18. Exercise, Obesity and Diets for Weight Loss

Having seen the Basics of Nutrition in the previous chapter, it is time to examine the causes of obesity and what can be done about it.
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There can be no doubt that overweight and obesity is a pandemic in the developed world.

Genetics or Environment?

It is very easy to blame our genes for making us overweight, and they do increase the risk. A study gives evidence that genetically predisposed people are at greater risk for higher BMI and that genetic predisposition interacts with bad diet resulting in higher BMI, as observed between the mid-1980s and mid-2000s. Nevertheless, BMI has increased for both genetically predisposed and non-predisposed people, implying that the environment remains the main contributor.1Quantifying the impact of genes on body mass index during the obesity epidemic Over the past 60 years, the gene pool of this country has not changed much, but the prevalence of obesity has risen enormously.

The following table shows levels of obesity in England by age group. The source is the NHS Digital, Health Survey for England 2019. It is possible that the level of obesity, which rises with age, falls in those who are 75 and over because the obese often do not live to that age group.

Age Cohort Underweight Normal Overweight Obese
16-24 7% 56% 24% 13%
25-34 0 42% 35% 23%
35-44 2% 34% 34% 30%
45-54 0 27% 40% 33%
55-64 0 27% 39% 34%
65-74 2% 23% 39% 36%
75+ 1% 28% 45% 26%

The European Union produced figures on obesity for member nations from 2008/2009, published in 2011.2British women ‘the fattest in Europe’ They showed that British women had the highest incidence of obesity at 23.9%. British men came second with 22.1%, behind Malta at 24.7%. However, the following, rather newer table, suggests others are now ahead of us.

European table of overweight and obesity from 2011

What is causing the current epidemic of obesity? Is it affecting those who are genetically susceptible or is it simply a self-inflicted condition? A report of a debate at the Society for Endocrinology in 2019 makes interesting reading.3 Nature vs Nurture: What’s Fuelling the Obesity Epidemic? It seems that there is an interplay between our genes and environment which affects obesity. Genes which may well have been beneficial in times when poor harvests and starvation were common, may now be predisposing us to obesity in a world of plenty. This may also explain why people of Indian race are more susceptible to diabetes and heart disease. Identical twins reared apart were found to have a very similar body weight.4 Genetic and Environmental Influences on Eating Behavior – A Study of Twin Pairs Reared Apart or Reared Together Adopted children have been shown to have a similar weight to their biological, rather than adoptive, parents. 5Genes and the intergenerational transmission of BMI and obesity

Another speaker in the debate pointed to data from the World Obesity Federation on adult obesity which showed that, between the 1960s and 1990s, the prevalence of obesity topped more than 15% in only a few developed countries and no developing nations but from 2000 onwards, the situation has changed. At least 15% of the population is obese in most developed countries, rising to over 25% in the United States, Canada, Australia, and the UK, among others. The prevalence of obesity is also rising rapidly in many middle-income countries.

We now walk about a Marathon a week less than we used to

Exercise matters too. It is estimated that, compared with the 1950s, the average adult now walks about 26 miles or a marathon less per week. In the 1960s, there was a sudden end to Soviet subsidies to Cuba which led to food shortages, the loss of public and private transport, and the import of 1.5 million bicycles from China. The subsequent drop in the prevalence of obesity was associated with a reduction in the incidence of diabetes and diabetes-related mortality. All three increasing substantially when food and transport levels were restored.

Obese parents give their habits to their children

It is thought that about 40% of weight is due to genetics and hence 60% is due to environmental factors. Both sides in the debate seemed to be eager not to blame the individual but to blame the genes or environment. This does not mean that the individual is powerless to do anything. That is obviously untrue. An article called 6Obesity Epidemic and Junk Food Consumption Go Hand in Hand makes it clear that junk food has much to do with obesity. It clearly contributes to a poor gut biome which we have seen has in Basics of Nutrition has an adverse effect on weight.

Several medical institutions have declared obesity to be a disease rather than a choice. 7 Is Obesity a Disease or a Choice? The causes have many factors and a multi-faceted approach is required. It is still up to the individual to do things for himself. Eat a good diet of proper food rather than take-aways. Keep fat and sugar down and limit processed food. Keep fibre up. Maintain healthy exercise. It is all too easy to become overweight or obese today, but it is up to the individual to correct it.

Obesity in pregnancy causes many complications

Obesity is a considerable problem in young women who are pregnant. UK figures from 2018 showed around 22% of pregnant women were obese, 28% overweight, and 47% within a normal range. Presumably, the outstanding 3% were underweight. This means that half were overweight or obese at booking for antenatal care. Complications for women who were obese included higher risk of miscarriage, stillbirth, pre-eclampsia, gestational diabetes, and postpartum haemorrhage (severe bleeding after delivery), while babies who had obese mothers had an increased risk of congenital anomalies, being born early, being a large baby (which is not healthy), becoming obese themselves, and having diabetes in later life.8Care of Women with Obesity in Pregnancy

Are we making our children fat?

The diet in pregnancy can have a long-term effect on the developing baby. Exposure to higher levels of glucose increases the risk of childhood obesity.9Maternal glucose levels during pregnancy and childhood adiposity in the Hyperglycemia and Adverse Pregnancy Outcome This occurs with glucose levels which are lower than those often found in diabetes. High glucose levels increase the number of fat cells in the baby.

A study of 2.8 million people, reported by the BBC in 2019 highlighted the scale of the obesity problem in the UK, with a significant risk of death and disease attached to weight gain.10Obesity: Study of 2.8 million shows increased disease and death risks Even a BMI of 25 to 30 doubled the risk of type 2 diabetes.

Obesity is also linked to depression in children and from the age of seven, mental health and obesity appear to be entwined and exacerbate each other.11Obesity and depression ‘hand-in-hand’ in children The importance of bacteria in the gut, called the biome, has been noted in the previous chapter Basics of Nutrition. The link between a poor biome and depression is discussed in the next chapter Diets and Nutrition for Health and Fitness. The abysmal diet, so often seen in adolescence is associated with both obesity and depression. A review called 12Microbiome and Mental Health, Specifically as It Relates to Adolescents suggested that the poor diets that are so common among adolescents may contribute to the rise in depression in this age group.

What many young people eat is appalling

Obesity is linked to several cancers as shown on the Cancer Research UK website.13Overweight and obesity statistics As smoking becomes less prevalent but obesity is a growing problem, the number of cancers attributable to smoking falls while the number attributable to obesity is rising.

Picture from the European Day of Obesity shows some of the complications. It should also include cancer

A review concluded, “Cancer in young adults, is occurring with increasing frequency. Overweight and obesity has become a major public health issue reaching pandemic proportions. Excess weight is associated with increased cancer risk, morbidity and mortality. Animal models indicate that obesity not only increases cancer incidence, but also accelerates its development. Thus, the possibility exists that overweight and obesity may be contributing to the appearance of specific malignancies at younger ages. This prospect, in association with the worldwide expansion of obesity, suggests an impending explosive increase in obesity associated cancers in young adults.”14Young Adult Cancer: Influence of the Obesity Pandemic As the incidence of smoking declines and the incidence of obesity rises, it is estimated that before long, obesity will overtake smoking as the most common avoidable cause of cancer.

Another possible contributor to obesity is sleep deprivation. The hormones leptin and ghrelin control appetite. Ghrelin increases hunger whilst leptin causes satiety and a feeling of hunger satisfaction. Sleep deprivation is associated with decreased leptin levels, increased ghrelin levels, and increased hunger and appetite.15Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite This is one of many papers that confirm this association and confirm the relationship between sleep deprivation and obesity.16The impact of sleep duration on adiposity and components of energy balance

I remember from days as a junior hospital doctor, that a hearty breakfast would help to alleviate the feeling of sleep deprivation. After a full day and a long night and with another day of work to follow, perhaps at 6am I would ask myself if I should take one hour of sleep but I would decide that this would probably make me feel worse. Instead, a bath and a cooked breakfast were a better approach.

It seems that people sleep less than they used to and as sleep has declined, obesity has risen. The two may well be related.17The epidemiology of sleep and obesity In adolescents, sleep disturbance is associated with other issues too.18Insufficient sleep in adolescents: causes and consequences The use of electronic media, and caffeine intake may contribute. Consequences range from inattentiveness, poor mental functioning and poor academic performance to increased risk of obesity and mood disturbances.

The results of studies about sleep deprivation and calorie intake and weight gain are often contradictory. Hence a review called 19The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis was interesting. It concluded that the pooled data from trials suggests that sleep deprivation leads to increased energy intake with no change in energy expenditure and increased weight. Some have found that late snacking is much more common with sleep deprivation and this is a bad time to eat.

Poor sleep and obesity are related in old people.20Is poor sleep associated with obesity in older adults?

Obesity increases the risk of snoring and sleep apnoea. The latter is when a person stops breathing during sleep.

The prevalence of obesity rises with falling income

Before the 20th century, the lower social classes were thin and obesity was the middle-class flaunting their ability to over-feed. Anyone who looks at photographs from before the 1940s, will be impressed by how few fat people there were. Now, obesity is more prevalent in lower social classes although by no means limited to them.

This reversal of association between weight with social class also applies to children. A study which spanned 1953 to 2015, included data from children born in England, Scotland and Wales who were enrolled in 4 birth cohort studies beginning in 1946, 1958, 1970, and 2001.21Socioeconomic inequalities in childhood and adolescent body-mass index, weight, and height from 1953 to 2015 A total of 22,500 children had their height and weight recorded and their BMI (body mass index) calculated at the age of 7 years, 34,873 at age 11, and 26,128 were assessed at age 15. The father’s occupation was used to assess social class, although the results remained the same when repeated using the mother’s education level.

Obesity is more common in deprived children

In the 1946, 1958 and 1970 groups, being a child or adolescent from a poorer background was associated with lower weight but by 2001 it was associated with higher weight. In the 1946 group the most disadvantaged 11-year olds weighed 2kg less than the least disadvantaged children. However, in the 2001 group, the most disadvantaged 11-year olds weighed 2.1kg more than the least disadvantaged children.

Even in childhood, obesity is an increasing problem and it heralds big problems for the future as fat children usually become fat adults

Throughout this time, in all groups, the most disadvantaged children tended to be shorter than the least disadvantaged children although the difference narrowed over time. In 1946 the most disadvantaged 7-year olds were 3.9cm shorter than the least disadvantaged children, whereas the difference in the 2001 group was just 1.2cm. I am a little surprised that the socially disadvantaged groups had not overtaken the more affluent for height as overweight or obese children tend to be comparatively tall. Thus, the weight may be on the 90th centile but height is on the 70 th centile. Perhaps this indicates that the diet is poor despite being high in Calories. War-time rationing did not end until 1954. At the time, diets typically included more vegetables, less sugar, and fewer soft drinks than today.


The mathematics is simple. If we take in more Calories than we use, we gain weight. If we take in fewer Calories than we use, we lose weight. Therefore, we should look at both sides of the equation. The first law of thermodynamics states that energy can neither be created nor destroyed.

Where possible, weight loss diets should be accompanied by exercise. However, the number of calories that must be burned to make a significant difference to weight is very disheartening. Thus, a good workout in the gym or elsewhere may be 500 Calories or even 800 or more for the energetic. If 100 grams of fat gives 930 calories, then to burn a kilogram of fat takes 9,300 Calories. This is disappointing. However, exercise has benefits above and beyond simply burning Calories.

Exercise and diet should be used together

Exercise is good for us. That is beyond reasonable doubt. However, exercise alone as a means of losing weight may be more difficult than we suppose, especially if exercise gives us an increased appetite. When Calorie intake is reduced, the body goes into starvation mode and the basal metabolic rate (BMR) slows. This means the baseline rate of using Calories, just sitting quietly in a warm room. A meta-analysis has shown that at least in the middle-aged women in the study, BMR does slow with diet alone but diet and exercise reduce this fall.22Effects of diet and diet-plus-exercise programs on resting metabolic rate Considering the importance of this observation it seems to be remarkably under-investigated. Exercise during dieting may also help to reduce muscle loss.

A trial comprised 25 men and 40 women aged 19 to 48 who were moderately obese and on a moderately strict diet. One group did aerobic exercise and the other did strength training. The resting metabolic rate declined in both groups by a similar amount. They lost a similar amount of weight. The aerobic exercise group became more fit as indicated by peak oxygen consumption. The muscle strength group lost less lean body weight.23Effects of strength or aerobic training on body composition, resting metabolic rate, and peak oxygen consumption in obese dieting subjects From this it appears that exercise does reduce the slowing of the resting metabolic rate during dieting. Aerobic exercise will burn more calories per session and increase physical fitness. Strength training will reduce the loss of muscle during dieting.

Cardio, weights or both?

Both strength training and aerobic exercise are associated with a lower prevalence of obesity, but which should we choose? Most of the evidence around exercise for health is based on aerobic exercise like walking, cycling, and jogging. A very large survey from the USA of roughly 1.7 million adults found that those who did at least 150 minutes of aerobic activity a week plus two muscle-strengthening exercises per week had the lowest prevalence of obesity. 24 Muscle Strengthening, Aerobic Exercise, and Obesity: A Pooled Analysis of 1.7 Million US Adults The aerobic exercise is described as moderate to vigorous. Therefore, it should not be a choice between either aerobic exercise or strength training, but we should do both. The survey found that the greater the level of obesity, the greater the benefit from combining both modalities. An editorial said that this was by far the largest study of its kind and it supports the concept of combining the two.

One problem is that BMI does not differentiate between weight from fat and weight from lean muscle mass. Lean muscle mass is raised by muscle training, but the weight training was still found to be associated with a lower risk of obesity as defined by BMI.

The researchers pooled data on 1,677,108 adults age 18 years and older from four US Behavioural Risk Factor Surveillance System (BRFSS) surveys for 2011, 2013, 2015, and 2017. Just over a quarter of respondents were 65 years or older, 51.6% were female, and most were white or Hispanic. More than half had never smoked, and 18.6% reported “excellent” health. There were 40% who did not meet guidelines for aerobic or strength-training exercise, 9.5% met strength-training guidelines only, 30.2% met aerobic guidelines only, and 20.2% met guidelines for both. Gender, socioeconomic status, education, lifestyle characteristics, and chronic health conditions, did not affect the results. In short, this recommendation should be for everyone, regardless of age, gender or race. This is not a prospective, controlled study, but it still offers very good evidence and the size of the study makes it by far the most convincing to date. Very often, in the gym, I see men doing weight training only and women doing cardio training only. Both should do both, but women should have less iron on the bar.

Age is no bar to exercise but be sensible

Humans have evolved over many millennia to be physically active. We have not evolved as couch potatoes. Exercise is good for us. Lack of exercise or indolence predisposes to weight gain, heart disease and type 2 diabetes. As we get older, both body and mind tend to deteriorate and the adage of “use it or lose it” rings true. However, there are more papers to support physical exercise than mental exercise to keep the brain functioning well, but I think the main reason for this is that physical activity has been much more actively researched. A paper showed that both aerobic training and stretching and toning have a beneficial effect in previously sedentary people with memory impairment over the course of 12 months, but it does not slow the deposition of beta amyloid in the brain. This is a crucial feature of Alzheimer’s disease.25Exercise Training in Amnestic Mild Cognitive Impairment I do not think that exercise will prevent Alzheimer’s disease, which is a very specific disease and not just natural aging, but for most of us it is helpful to slow the natural decay.

Dancing of any sort is helpful in older age groups

Both learning a musical instrument26Older adults benefit from music training early in life and learning a foreign language27Language Training Leads to Global Cognitive Improvement in Older Adults are said to be helpful to stave off the mental ravages of the years. I also recommend ballroom dancing as it offers aerobic exercise, strength, balance, coordination and the ability to learn new tasks as well as social interaction.

An article in The Times was called 28Don’t bother with brain supplements: exercise is best for dementia. It said that “Health-store shelves and websites are crowded with costly brain-boosting, cognitive-supporting supplements with seductive formulations of omega 3, vitamin B12 and healthful exotics such as ginkgo biloba, green tea essence, curcumin and turmeric.” It went on to explain that these are all quite useless, quoting many authorities. The best treatment is physical exercise. The marketing of these products is a cause for concern.

Find an exercise that is appropriate for you and you enjoy

Exercise effects the bacteria in the gut with a positive effect on health.29Exercise Modifies the Gut Microbiota with Positive Health Effects This includes both weight loss and reduction in risk factors for coronary and other disease. Moderate intensity exercise can reduce hunger, limit food intake and aid weight loss.30Effects of exercise on gut peptides, energy intake and appetite

Some people carry a gene called FTO which makes them genetically susceptible to obesity. It has often been thought that in such people, exercise does not have much benefit. However, a massive meta-analysis, based on more than 200,000 adults and nearly 20,000 children and adolescents found that the odds of obesity is reduced by 27% in physically active adults with this gene.31Physical activity attenuates the influence of FTO variants on obesity risk The conclusion was that it is extremely important for susceptible people to keep active.

Aerobic exercise plus resistance exercise has been assessed in overweight and obese youth with a meta-analysis. It appears to be effective in lowering body weight, body mass index (BMI) and body fat, especially if the sessions were at least an hour long.32Effects of Aerobic Plus Resistance Exercise on Body Composition in Pediatric Obesity Recommendations are that alongside aerobic exercise, there should be some weight training for better effect.

Usually, when advising exercise, the term aerobic exercise is used. This means that it can be kept up for quite a long time as with a brisk walk, a cycle ride or a long-distance run. There is not much “oxygen debt” and lactic acid does not build up to any significant level. Anaerobic exercise is a sprint and builds up an “oxygen debt” so that it is not possible to tolerate it for very long. In athletics, the event which produces the highest level of blood lactic acid at the finish is the 400 metres. Interval training is a type of training that involves a series of high- and low-intensity workouts interspersed with rest or relief periods. They are very demanding of physical fitness. Because of the emphasis on aerobic exercise, we tend to ignore high-intensity or anaerobic exercise.

HIIT workouts are very demanding

High intensity interval training (HIIT) is popular nowadays and it does seem to be better than moderate-intensity continuous training for burning fat. A systematic review found that interval training provided 28.5% greater reductions in total absolute fat mass than moderate continuous exercise.33Is interval training the magic bullet for fat loss? One reason for the popularity of HIIT in a busy world is that it does not take long. However, it is very intensive and may not be suitable for those who are not already quite fit and those with a few years behind them. Other techniques are effective, including endurance and resistance training (doing weights).34Effect of combined resistance and endurance exercise training on regional fat loss. In the past the emphasis has always been on aerobic exercise, but HIIT includes anaerobic exercise with recovery.

Exercise does affect the hormones that control appetite but the nature of this is rather complex and at present unclear.35Effects of exercise intensity on plasma concentrations of appetite-regulating hormones. Sometimes we have a greater appetite after exercising but for those who use exercise with diet to lose weight, it seems to improve appetite control.

Very serious athletes, including many professionals, can suffer a variety of problems in their career. A systematic review starts with the statement, “Fatigue, mood disturbances, under performance and gastrointestinal distress are common among athletes during training and competition.” They go on to explain that the bacteria in the gut effect the release of various hormones. Physical and emotional stress can also have an effect. They note that dietary recommendations for elite athletes include a low consumption of plant polysaccharides (starch and fibre).36Exercise-induced stress behavior, gut-microbiota-brain axis and diet Again, it seems that advice to athletes is not as scientifically robust as may be expected.


The concept of mens sans in corpore sano (a healthy mind in a healthy body) has been acknowledged for millennia. As Cicero observed around 65BC, “It is exercise alone that supports the spirits, and keeps the mind in vigour.” Exercise has beneficial effects on academic performance.37Be smart, exercise your heart: exercise effects on brain and cognition

Patients with cancer often get toxic effects on their hearts from the chemotherapy drugs that are used. These adverse effects can be limited by exercise and exercise training before treatment has been advocated.38The benefits of exercise in cancer patients As noted above, exercise may also improve the gut biome and help to reduce effects on the bowel from radiotherapy.

Football teams have started for men with prostate cancer

A statement from multiple organisations around the world says that exercise is of value in reducing the risk of many cancers and in helping the prognosis of those who have them. A commentary on the paper said that if exercise were a drug, there would be enormous pressure to prescribe it. Exercise improves fatigue, anxiety, depression, function, and quality of life. However, most people living with and beyond cancer are not regularly physically active. What is required is a cultural change in which people with cancers do not see themselves as too debilitated to exercise, but they see it as a way to improve their resistance to the disease along with their quality of life.39Exercise is medicine in oncology In a paper from Denmark which described a group of men with prostate cancer who started a football team, one was quoted as saying, “I would rather die on the football pitch than in a hospice.”

Weight bearing exercise is important to prevent osteoporosis

Exercise appears to have a beneficial effect on preventing or slowing osteoporosis in post-menopausal women.40The Effectiveness of Combined Exercise Interventions for Preventing Postmenopausal Bone Loss Weight bearing exercise is best and the benefit seems to be limited to the area of the exercise. Water based exercise is less effective than weight bearing exercise.41Effects of water-based exercise on bone health of middle-aged and older adults Most of the evidence relates to women with very little about men although they represent 15% of cases of osteoporosis. Exercise in older people also improves strength and balance, reducing the risk of falls, and if osteoporosis is reduced, even if they do fall, they are less likely to sustain a fracture.42Interventions to Prevent Falls in Older Adults

In summary, exercise is very important for weight control and modification of risk factors for various diseases. This is not so much because of the number of Calories burned during the exercise, but the effect on the gut biome and the many implications of this. They include appetite control, often a greater feeling of well-being and a generally healthier lifestyle.

Weight Loss Diets

Yo-yo dieting must be avoided

The fact that there are so many weight loss diets shows that there are an enormous number of people seeking to lose weight and that no diet is totally satisfactory for all. If any diet did what was claimed for everyone, it would have cornered the market. Most people lose weight then gain it again. This is called “yo-yo dieting”. It is said that 94% of weight losers have regained the weight within five years. As a business model, this is wonderful news for the market in weight loss as it means that customers keep returning.

When people start to diet, weight loss is often quite fast, and they then become disenchanted as it slows. In the early stages, much of what is lost is not fat. For example, middle aged and older women who are overweight or obese often have swollen legs, as do a significant number of overweight or obese men. This is called oedema. Many more may be retaining water but not enough to cause such obvious swelling. Sometimes diuretics are prescribed to make them pass more urine to get rid of this water but soon the tablets lose their effect. The only effective way to lose the water is to lose weight. Again, this is a poorly researched area. People who lose weight do see a reduction in total body water.43Effect of weight reduction on the renin-aldosterone axis This may account for some of the early rapid weight loss. A litre of water weighs a kilogram.

Failed weight loss is a standing joke

If a person goes on a diet with significant calorie restriction, the body goes into “famine mode” and the general rate of burning calories, called the basal metabolic rate, reduces. This makes it more difficult to lose weight. This is based on evidence, much of it going back quite a long way. In the Minnesota starvation experiment in the 1940s, participants were fed an extreme low-calorie diet, 44 Overfeeding Studies but in the Vermont prison over-feeding study in the 1960s, inmates were fed up to 10,000 calories a day. 45 The Vermont Prison Overfeeding Study People did not lose as much weight as might be expected on a starvation regime and people did not gain as much weight as might be expect with marked overeating. In both cases, I have been unable to get the original paper, so I have had to rely on websites that discuss them.

When people go on a strict diet to lose weight, they are hampered by the body’s metabolic rate slowing down. Furthermore, this can be prolonged and irreversible. A study based on the American show “The Biggest Loser” in which contestant compete to lose vast amounts of weight, found that six years later, their bodies were still in low metabolic rate mode.46Persistent metabolic adaptation 6 years after “The Biggest Loser” competition.

Take-away meals are extremely popular with a great many busy, working people opting for the convenience over shopping and cooking, both for themselves and their families. This leads to very poor nutrition with its attendant problems such as obesity and poor sleep and mental function. As well as often being highly processed foods, the Calorie content can be very high. A stuffed crust pizza may contain nearly 2,000 Calories. For people who like the food, the equivalent ready-meal in a supermarket often contains far fewer Calories. As for those who equate vegan with healthy, vegan dishes often contain rather more Calories than the meat equivalent.

Sugar, which normally means table sugar or sucrose, is a rapid source of calories that offers nothing else in terms of nutrition. It is rapidly absorbed, blood glucose rises quickly, insulin is produced and fat is laid down. It makes sense to cut out these “empty” calories but often people have a craving for sweetness and the obvious solution would seem to be artificial sweeteners. For example, sucralose is a molecule that will stimulate the taste buds in the same way as sucrose but it does not give calories. However, there is a problem with artificial sweeteners.

Artificial sweeteners may increase appetite

Artificial sweeteners can increase appetite. People were given a drink that was sweetened with either sucralose (an artificial sweetener) or sucrose (ordinary sugar). They were then invited to help themselves to a buffet and what they consumed was noted. They found that drinking artificially sweetened drinks may trick the brain into feeling hungry, which may in turn result in more calories being consumed. There were two groups that were particularly susceptible. One was women. The other was those who were obese.47Obesity and Sex-Related Associations With Differential Effects of Sucralose vs Sucrose on Appetite and Reward Processing. A Randomized Crossover Trial. It seems that people should try to give up their quest for sweetness and not just replace sugar with sweeteners. Those who have given up sugar in tea and coffee can attest that after a while they find tea or coffee with sugar to be unpleasant.

It is not enough to lose the weight. It must be kept off

Being overweight or obese is a chronic problem. Therefore, when looking for a suitable diet, think long term. Any diet that cuts out whole food groups should be rejected. The Atkins Diet which cuts out carbohydrates is an example. It may also exacerbate muscle loss. It is a very unpleasant diet with an even higher drop-out rate than most. Avoid fad diets and those promoted by celebrities. Celebrity status allows people to pontificate on subjects that they know nothing about, and people still take them seriously. Very low-calorie diets such as the Cambridge diet may have a limited place, but generally a less ambitious and more achievable diet should be sought. Excessive Calorie counting should be avoided as it causes preoccupation with food.

Opinions vary about Weight Watchers and the like

Groups such as Weight Watchers do not promote a specific diet but offer support. Many people find the encouragement and advice very useful. They seem to be successful in that people lose weight, but they still have more than 90% regaining the weight within five years.

Almost anyone can write a book about their own “sure way” to lose weight and people will buy it. Remember the basic science and the principles and do not be deceived by charlatans. An American meta-analysis and review of diets concluded that “Significant weight loss was observed with any low-carbohydrate or low-fat diet. Weight loss differences between individual named diets were small. This supports the practice of recommending any diet that a patient will adhere to in order to lose weight.”48Comparison of weight loss among named diet programs in overweight and obese adults

Breakfast and Dinner- The Two Most Important Meals

Breakfast been said to be most important meal since 1917. A study called “Effect of breakfast on weight and energy intake: systematic review and meta-analysis of randomised controlled trials” confirmed this but the researchers warned that their findings should be treated with caution, as the quality of the studies in the meta-analysis is low: all 13 studies they included were at a high or unclear risk of bias.49Effect of breakfast on weight and energy intake In a blog called “Breakfast—the most important meal of the day?” Professor Tim Spector agrees.50Breakfast—the most important meal of the day?

The time of dinner is important

Another meal to consider is dinner. A randomised cross-over clinical trial examined the issue. They recruited 10 healthy men and 10 healthy women, with an age around 26.0 and a BMI around BMI 23 or 24 who usually went to bed between 10pm and 1am. The cross-over trial involved them eating dinner at either 6pm or 10pm, without changing the calorie or basic nutritional content of dinner. Both that night and the next morning they checked hourly plasma glucose, insulin, triglycerides, free fatty acids (FFAs), cortisol and dietary fatty acid oxidation. They also did overnight polysomnography to assess the quality of sleep.

The late dining caused a shift in the after dinner metabolism which overlapped with the sleep. Independent of this, the postprandial (after food) period following a late dinner saw higher glucose, a triglyceride peak delay, and lower free fatty acids and dietary fatty acid oxidation. Late dining did not affect sleep, but it increased plasma cortisol. The conclusion was that late dining induces nocturnal glucose intolerance, and impairs fat metabolism. If this is habitual, it may promote obesity.51Metabolic Effects of Late Dinner in Healthy Volunteers This may also imply that late night snacks are bad.

Have an early dinner around 6pm and a good breakfast.

Drugs to Aid Weight Loss

Drugs are not the answer to weight loss

The use of drugs to aid weight loss has not been very successful. The earliest drugs were amphetamines. They were effective in suppressing appetite but with considerable adverse effects. This includes hyperactivity, insomnia, addiction and depression on ceasing the drug. I expect that most people will recognise the spelling as amphetamines but nowadays the British National Formulary (BNF) spells them as amfetamines. They are in class B of controlled drugs along with barbiturates, cannabis and dihydrocodeine. Phenteramine and ionamine were really no better and are not in the current BNF. The BNF says, “Various centrally acting (acting on the brain) appetite suppressants, including stimulants and serotonergic drugs (such as dexfenfluramine, fenfluramine, sibutramine, and rimonabant), have been used in the management of obesity but have been withdrawn or are no longer recommended due to serious safety concerns or their addictive potential.”

Substances such as methylcellulose and sterculia which produce a feeling of fullness have not been licensed for use as there is little evidence that they are effective.

There are a great many desperate people who are vulnerable to the claims of the snake oil salesmen. As usual, beware those whose claims are too good to be true. Beware those who trumpet the latest “scientific advances” that even your doctor has not yet heard of. Beware those who say that you can eat whatever you like and lose weight or those who offer herbs to make you lose weight. Tablets to suppress the appetite are related to the amphetamines and like them have unacceptable effects including addiction and depression on stopping them.52Obesity drug therapy Other combinations including caffeine, ephedrine and thyroid extract have been used but these have never been approved as any effect is minimal whilst side effects and dangers are significant, especially if there is any heart problem. Any drugs that increase the metabolic rate, including caffeine and thyroid tablets have side-effects beyond their tiny benefit.

A drug called orlistat reduces the absorption of fat from the gut.53Obesity. NHS Choices It is imperative to stick to a very low fat diet or it has very unpleasant side-effects. Some argue that it works by enforcing a low-fat diet as any breach is severely punished. It is now available without a prescription.

Swollen ankle are common with overweight

People who are overweight often retain water and this may produce ankle swelling called oedema. This is especially common in middle-aged or older women, but it can occur in anyone of either gender or at any age. Diuretics, which are tablets to make the kidneys excrete more urine may apparently have early success in that oedema reduces and weight falls. A litre of water weighs one kilogram. However, it is only water that is lost, not fat, and after a while the diuretics cease to be effective.

The only drug that is currently licenced for weight loss is orlistat. This has a novel approach in that it impairs the absorption of fat. Therefore, anyone who takes it must stick to a low-fat diet or the result is called steatorrhoea. This is very unpleasant with a type of diarrhoea that it fatty and frothy. It floats and is difficult to flush away. It leaves a greasy stain round the pan. Some people argue that it works by making the user adhere to a low-fat diet or there is punishment. There are three classifications of medicines. POM or prescription-only medicines need a doctor’s prescription. P can be sold by a pharmacist. OTC or over the counter can be sold anywhere, including supermarkets. Orlistat is classified as P.

A paper from 2021 has suggested that a high dose of caffeine before exercise may improve fat burning although the question mark in the title may suggest that even the authors are sceptical.54Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation? Fifteen men took 3mg per kg body weight of green coffee bean powder, which is about the equivalent of a strong coffee, or a placebo dissolved in water. Each person completed the test under all four conditions of active or placebo and at 8am or 5pm. Overall, the dose of caffeine 30 minutes before an aerobic workout increased fat oxidation during exercise at both times of day. Compared to the placebo, caffeine increased fat oxidation by 10.7% in the morning and 29% in the afternoon. Caffeine also increased exercise intensity by 11% in the morning and 13% in the afternoon. The maximum oxygen uptake was also higher in the afternoon. It will be interesting to see if others confirm this finding from the University of Granada. Note that this is about a high dose of caffeine combined with exercise, not caffeine alone.

Herbs to Aid Weight Loss

Over the years, many herbs and supplements have been advocated to aid weight loss. They are usually claimed to increase the metabolic rate and hence to burn Calories faster.

The first systematic review and meta-analysis for nearly 20 years of herbal products to aid weight loss was published in early 2020.55Effectiveness of herbal medicines for weight loss: A systematic review and meta-analysis of randomized controlled trials It was a substantial piece of work which included:

  • Green tea (12 studies)
  • Malabar tamarind (11 studies)
  • White kidney bean (seven studies)
  • Ephedra (five studies)
  • African mango (three studies)
  • Yerba mate (three studies)
  • Veld grape (two studies)
  • Licorice (two studies)
  • Mangosteen (two studies)
  • Miscellaneous herbal medicines (17 studies)

Statistically and clinically significant weight loss was reported for some products that were studied in three or fewer trials, but the investigators advised cautious interpretation because of the small number of studies, poor methodology, and poor reporting of herbal medicine interventions. Once again, the problem is poor quality studies. Their conclusion was that they could not recommend any of the interventions.

There are plenty of “natural” weight loss products, all without evidence and they may be dangerous

For those who wish to try these substances, thinking that even if they do not work, there will be no harm, there is bad news. Many of these substances have been associated with adverse effects, especially damage to the liver. Furthermore, when patients see a doctor with symptoms of these problems, they may fail to tell that they have been using them. This may be because they cannot believe that something that is “natural” can also be deadly. Approximately 10% of cases associated with green tea extract have been fatal.56Liver injury from herbals and dietary supplements

This heading and the contents are reproduced in the chapter Herbal Remedies. You may wish to look at that chapter for further information.

Bariatric or Weight Loss Surgery

An intervention for obesity that must not be overlooked is surgery. This is often called bariatric surgery. It may seem rather excessive if obesity can be managed by diet and lifestyle alone but, in reality, it can produce better results than other interventions and the results last long-term. In people who are morbidly obese or who have obesity and type-2 diabetes, NICE is encouraging. 57NICE CG189 Weight loss surgery is also discussed on the NHS website. 58 Weight loss surgery

They state that weight loss surgery is available on the NHS if:

  • A person has a BMI of 40 or more (morbidly obese), or a BMI between 35 and 40 and an obesity-related condition that might improve with weight loss such as type 2 diabetes or high blood pressure.
  • Possibly for a person who has tried all other weight loss methods, such as dieting and exercise, but has struggled to lose weight or keep it off.
  • It requires long-term follow-up after surgery including making healthy lifestyle changes and attending regular check-ups.

There are various types of bariatric surgery, but the most common types are:

  • Gastric band in which a band is placed around the stomach to produce an earlier feeling of fullness.
  • Gastric bypass where the top part of the stomach is joined to the small intestine. This also produces earlier feeling of fullness plus it reduces the number of calories absorbed from food.
  • Sleeve gastrectomy is when some of the stomach is removed. It also leads to earlier feeling of fullness.

The three main types of bariatric surgery

All these operations can lead to significant weight loss within a few years, but each has advantages and disadvantages. I do not wish to go into detail about the procedures, but they can be very effective where all else has failed, and obesity is often a very refractory condition.

The effects can be long lasting. NICE finds that with suitable selection, they are cost-effective. They are a last resort but a good last resort.

As with all surgery, there can be complications and the patients are very obese and so at high risk with any surgical procedure.

Further Resources


  1. Brandkvist M, Bjørngaard JH, Ødegård RA, Åsvold BO, Sund ER, Vie GÅ Quantifying the impact of genes on body mass index during the obesity epidemic: longitudinal findings from the HUNT Study BMJ. 2019 Jul 3;366:l4067 [full text]
  2. British women ‘the fattest in Europe’ The Times 26th November 2011
  3. Nature vs Nurture: What’s Fueling the Obesity Epidemic? Medscape 22 November 2019
  4. Elder SJ, Neale MC, Fuss PJ, Lichtenstein AH, Greenberg AS, McCrory MA et al. Genetic and Environmental Influences on Eating Behavior – A Study of Twin Pairs Reared Apart or Reared Together. Open Nutr J. 2012 Apr 6;6:59-70. [full text]
  5. Classen TJ, Thompson O. Genes and the intergenerational transmission of BMI and obesity. Econ Hum Biol. 2016 Dec;23:121-133
  6. Obesity Epidemic and Junk Food Consumption Go Hand in Hand. Medscape 10 January 2020.
  7. Is Obesity a Disease or a Choice? Medscape 25 July 2018.
  8. Denison FC, Aedla NR, Keag O, Hor K, Reynolds RM, Milne A, Diamond A. RCOG Green‐top Guideline No. 72 Care of Women with Obesity in Pregnancy. Royal College of Obstetricians and Gynaecologists. 21 November 2018
  9. Lowe WL Jr, Lowe LP, Kuang A, Catalano PM, Nodzenski M, Talbot O, HAPO Follow-up Study Cooperative Research Group. Maternal glucose levels during pregnancy and childhood adiposity in the Hyperglycemia and Adverse Pregnancy Outcome Follow-up Study..Diabetologia. 2019 Apr;62(4):598-610. doi: 10.1007/s00125-018-4809-6. Epub 2019 Jan 15.[full text]
  10. Obesity: Study of 2.8 million shows increased disease and death risks BBC 29th April 2019
  11. Obesity and depression ‘hand-in-hand’ in children BBC 29th April 2019
  12. Simkin DR. Microbiome and Mental Health, Specifically as It Relates to Adolescents. Curr Psychiatry Rep. 2019 Sep 2;21(9):93
  13. Overweight and obesity statistics. Cancer Research UK
  14. Berger NA. Young Adult Cancer: Influence of the Obesity Pandemic. Obesity (Silver Spring). 2018 Apr; 26(4): 641–650. [Full Text]
  15. Spiegel K, Tasali E, Penev P, Van Cauter E. Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004 Dec 7;141(11):846-50
  16. Capers PL, Fobian AD, Kaiser KA, Borah R, Allison DB. A systematic review and meta-analysis of randomized controlled trials of the impact of sleep duration on adiposity and components of energy balance. Obes Rev. 2015 Sep;16(9):771-82. [full text]
  17. Ogilvie RP, Patel SR. The epidemiology of sleep and obesity. Sleep Health. 2017 Oct;3(5):383-388 [full text]
  18. Owens JA, Weiss MR. Insufficient sleep in adolescents: causes and consequences. Minerva Pediatr. 2017 Aug;69(4):326-336
  19. Al Khatib HK, Harding SV, Darzi J, Pot GK. The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis. Eur J Clin Nutr. 2017 May;71(5):614-624
  20. Norton MC, Eleuteri S, Cerolini S, Ballesio A, Conte SC, Falaschi P, Lucidi F. Is poor sleep associated with obesity in older adults? A narrative review of the literature. Eat Weight Disord. 2018 Feb;23(1):23-38
  21. Bann D, Johnson W, Li L, Kuh D, Hardy R. Socioeconomic inequalities in childhood and adolescent body-mass index, weight, and height from 1953 to 2015: an analysis of four longitudinal, observational, British birth cohort studies. Lancet Public Health. 2018 Apr;3(4):e194-e203. [full text]
  22. Thompson JL, Manore MM, Thomas JR. Effects of diet and diet-plus-exercise programs on resting metabolic rate: a meta-analysis. Int J Sport Nutr. 1996 Mar;6(1):41-61
  23. Geliebter A, Maher MM, Gerace L, Gutin B, Heymsfield SB, Hashim SA. Effects of strength or aerobic training on body composition, resting metabolic rate, and peak oxygen consumption in obese dieting subjects. Am J Clin Nutr. 1997 Sep;66(3):557-63
  24. Bennie JA, De Cocker K, Pavey T, Stamatakis E, Biddle SJH, Ding D. Muscle Strengthening, Aerobic Exercise, and Obesity: A Pooled Analysis of 1.7 Million US Adults. Obesity (Silver Spring). 2020 Feb;28(2):371-378. [full text]
  25. Tarumi T, Rossetti H, Thomas BP, Harris T, Tseng BY, Turner M, et al. Exercise Training in Amnestic Mild Cognitive Impairment: A One-Year Randomized Controlled Trial. J Alzheimers Dis. 2019 Aug 8
  26. White-Schwoch T, Woodruff Carr K, Anderson S, Strait DL, Kraus N Older adults benefit from music training early in life: biological evidence for long-term training-driven plasticity. J Neurosci. 2013 Nov 6;33(45):17667-74 [full text]
  27. Wong PCM, Ou J, Pang CWY, Zhang L, Tse CS, Lam LCW, Antoniou M. Language Training Leads to Global Cognitive Improvement in Older Adults: A Preliminary Study. J Speech Lang Hear Res. 2019 Jul 15;62(7):2411-2424
  28. Don’t bother with brain supplements: exercise is best for dementia. The Times 8 March 2019
  29. Monda V, Villano I, Messina A, Valenzano A, Esposito T, Moscatelli F Exercise Modifies the Gut Microbiota with Positive Health Effects. Oxid Med Cell Longev. 2017;2017:3831972 [full text]
  30. Martins C, Morgan LM, Bloom SR, Robertson MD. Effects of exercise on gut peptides, energy intake and appetite. J Endocrinol. 2007 May;193(2):251-8
  31. Kilpeläinen TO, Qi L, Brage S, Sharp SJ, Sonestedt E, Demerath E, Ahmad T, Mora S, Kaakinen M, et al. Physical activity attenuates the influence of FTO variants on obesity risk: a meta-analysis of 218,166 adults and 19,268 children. PLoS Med. 2011 Nov;8(11):e1001116. [full text]
  32. García-Hermoso A, Sánchez-López M, Martínez-Vizcaíno V. Effects of Aerobic Plus Resistance Exercise on Body Composition Related Variables in Pediatric Obesity: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Pediatr Exerc Sci. 2015 Nov;27(4):431-40
  33. Viana RB, Naves JPA, Coswig VS, de Lira CAB, Steele J, Fisher JP, Gentil P. Is interval training the magic bullet for fat loss? A systematic review and meta-analysis comparing moderate-intensity continuous training with high-intensity interval training (HIIT) Br J Sports Med. 2019 May;53(10):655-664
  34. Scotto di Palumbo A, Guerra E, Orlandi C, Bazzucchi I, Sacchetti M. Effect of combined resistance and endurance exercise training on regional fat loss. J Sports Med Phys Fitness. 2017 Jun;57(6):794-801
  35. Hazell TJ, Islam H, Townsend LK, Schmale MS, Copeland JL. Effects of exercise intensity on plasma concentrations of appetite-regulating hormones: Potential mechanisms. Appetite. 2016 Mar 1;98:80-8.
  36. Clark A, Mach N. Exercise-induced stress behavior, gut-microbiota-brain axis and diet: a systematic review for athletes. J Int Soc Sports Nutr. 2016 Nov 24;13:43 [full text]
  37. Hillman CH, Erickson KI, Kramer AF. Be smart, exercise your heart: exercise effects on brain and cognition. Nat Rev Neurosci. 2008 Jan;9(1):58-65. Review
  38. D’Ascenzi F, Anselmi F, Fiorentini C, et al. The benefits of exercise in cancer patients and the criteria for exercise prescription in cardio-oncology. Eur J Prev Cardiol 7 October 2019
  39. Schmitz KH, Campbell AM, Stuiver MM, Pinto BM, Schwartz AL, Morris GS, Et al. Exercise is medicine in oncology: Engaging clinicians to help patients move through cancer. CA Cancer J Clin. 2019 Oct 16. [full text]
  40. Zhao R, Zhang M, Zhang Q. The Effectiveness of Combined Exercise Interventions for Preventing Postmenopausal Bone Loss: A Systematic Review and Meta-analysis. J Orthop Sports Phys Ther. 2017 Apr;47(4):241-251
  41. Simas V, Hing W, Pope R, Climstein M. Effects of water-based exercise on bone health of middle-aged and older adults: a systematic review and meta-analysis. Open Access J Sports Med. 2017 Mar 27;8:39-60. [full text]
  42. Guirguis-Blake JM, Michael YL, Perdue LA, Coppola EL, Beil TL. Interventions to Prevent Falls in Older Adults: Updated Evidence Report and Systematic Review for the US Preventive Services Task Force. JAMA. 2018 Apr 24;319(16):1705-1716
  43. Vaswani AN. Effect of weight reduction on the renin-aldosterone axis. J Am Coll Nutr. 1985;4(2):225-31
  44. Overfeeding Studies. United Nations University.
  45. Ideal Body Weights. The Vermont Prison Overfeeding Study.
  46. Fothergill E, Guo J, Howard L, Kerns JC, Knuth ND, Brychta R et al. Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity (Silver Spring). 2016 Aug;24(8):1612-9. [full text]
  47. Yunker AG, Alves JM, Luo S. Obesity and Sex-Related Associations With Differential Effects of Sucralose vs Sucrose on Appetite and Reward Processing. A Randomized Crossover Trial. JAMA Network Open. 2021;4(9):e2126313. doi:10.1001/jamanetworkopen.2021.26313 [full text]
  48. Johnston BC, Kanters S, Bandayrel K, Wu P, Naji F, Siemieniuk RA et al. Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA. 2014 Sep 3;312(9):923-33
  49. Sievert K, Hussain SM, Page MJ, Wang Y, Hughes HJ et al. Effect of breakfast on weight and energy intake: systematic review and meta-analysis of randomised controlled trials. BMJ 2019;364:l42
  50. Tim Spector: Breakfast—the most important meal of the day?
  51. Gu C, Brereton N, Schweitzer A, Cotter M, Duan D, Børsheim E, et al. Metabolic Effects of Late Dinner in Healthy Volunteers – A Randomized Crossover Clinical Trial J Clin Endocrinol Metab 2020 Jun 11;dgaa354.
  52. Baretić M. Obesity drug therapy. Minerva Endocrinol. 2013 Sep;38(3):245-54
  53. Obesity. NHS Choices
  54. Ramírez-Maldonado M, Juan del Coso L, Ruiz J, Amaro-Gahete FJ. Caffeine increases maximal fat oxidation during a graded exercise test: is there a diurnal variation? Journal of the International Society of Sports Nutrition volume 18, Article number: 5 (2021)
  55. Maunder A, Bessell E, Lauche R, Adams J, Sainsbury A, Fuller NR. Effectiveness of herbal medicines for weight loss: A systematic review and meta-analysis of randomized controlled trials. Diabetes Obes Metab. 2020 Jan 27. doi: 10.1111/dom.13973.[full text]
  56. Navarro VJ, Barnhart H, Bonkovsky HL, Davern T, Fontana RJ, Grant L, et al. Liver injury from herbals and dietary supplements in the U.S. Drug-Induced Liver Injury Network. Hepatology. 2014 Oct;60(4):1399-408. [full text]
  57. NICE. Obesity: identification, assessment and management. Clinical guideline [CG189]
  58. NHS Conditions. Overview-Weight loss surgery

Site Index

This website is now completed, although I shall continue to do updates. The following list shows the sections or chapters. Just click on the topic in blue to go to that part of the site.

1 Introduction
2 A Very Brief History of Science And Medicine
Fundamentals of Medical Science
3 Finding Good Medical Advice and Evidence Based Medicine
4 Randomised Controlled Trials
5 Cohort or Longitudinal and Epidemiological Studies
6 Qualitative Research
7 Basic Maths in Medical Research and Decision Making
8 How Good is the Evidence?
9 Ethics in Practice and Research
Public Health Issues
10 Screening Programmes
11 Fake News and Vaccine Scares
12 Electronic Cigarettes (E-Cigarettes)
13 Motor Vehicle Emissions, Air Pollution and Health
14 COVID-19. What You Need to Know
15 Who is at Risk from COVID-19
16 What we Must Learn from the COVID-19 Pandemic
17 Basics of Nutrition
18 Exercise, Obesity and Diets for Weight Loss
19 Diets and Nutrition for Health and Fitness
20 Supplements
Complementary and Alternative Medicine
21 Introduction to Alternative Healthcare
22 Homeopathy
23 Acupuncture
24 Manipulation of the Spine
25 Reflexology
26 Herbal Remedies
27 Other Natural Products
28 Chelation Therapy
29 Hypnosis
30 Other Modalities of Complementary and Alternative Medicine
Some Controversial Diseases
31 Fibromyalgia
32 Chronic Fatigue Syndrome (CFS) or Myalgic Encephalitis (ME)
33 Systemic Candidiasis and Leaky Gut Syndrome
34 Mobile Phones, Masts, Wi-Fi and Electro-sensitivity
The Environment
35 Global Warming and Climate Change
36 Alternative Energy
Some Final Thoughts
37 Still Searching for the Age of Reason