Australian scientists Garry Egger and Sam Egger separate truth from fiction in the quest for weight loss.
There is a great deal of misunderstanding about weight loss, which extends well beyond the public to health professionals. On one level, that is hardly surprising because the evidence can be very unclear. The science of health behaviour – including nutrition, exercise, sleep and weight management – is generally less developed than research relating to other medical questions. Unvetted ”expert” claims abound.
Commercial sponsors of weight-loss diets make loud proclamations for the superiority of their product but lifetime adherence to a restrictive diet – which is necessary to keep off weight once it is lost – is unrealistic for most people.
We assessed the best available evidence on weight loss and maintenance and used this to compile a 20-statement survey – with true or false responses – which we then gave to two groups of people: 173 GPs and 129 truck drivers and tradesmen.
We found doctors were almost as confused as truckies and tradies. The doctors disagreed with most of the supporting evidence on 40 per cent of our questions, the others on 49 per cent.
The statements below attracted the most incorrect answers, with our summary of evidence for and against them.
It seems doctors could benefit from more education and training in this area, and much more research into these questions is required, to confirm or challenge the accuracy of so-called ”facts” on which weight-loss advice is based.
Fruit juice is about as fattening as beer – TRUE
In terms of kilojoule content, equivalent servings of fruit juice and beer are similar. But as alcohol cannot be stored in the body, and is never directly converted to fat, any fattening effect of alcohol is dependent on other factors, particularly accompanying energy intake. So the often-quoted ”beer belly” is really more of a ”beer plus food and drink” belly. Fruit juice is as potentially fattening as beer in equivalent amounts.
Humans need eight glasses of water a day – FALSE
The physiologist Heinz Valtin tried to track the basis of this belief, which he claims may be responsible for the excessive intake of high-calorie fluids in the modern diet.
Valtin showed a person’s fluid needs depended on age, gender, activity level and state of health – as well as the weather – and varied from 500 millilitres (about three glasses) to four litres (24 glasses) a day. Despite the popularity of the eight glasses ”rule”, international guidelines on fluid intake, now under development, suggest it is arbitrary and meaningless.
Dairy products can help weight loss – TRUE
The accuracy of this statement remains controversial. Because of the fat content of most natural dairy products, a common belief exists that all dairy products cause weight gain. But recent research – both across communities and in dietary experiments with individuals – suggests eating low-fat dairy is linked to weight loss.
There are indications that certain dairy ingredients, such as whey protein, and combinations of ingredients, such as protein and calcium, can increase feelings of fullness, and increase the calories lost in the faeces – both of which may assist weight loss.
Chocolate is healthy provided it is dark – FALSE
There has been more than a decade of research on the health benefits of dark chocolate since the antioxidant effects of cocoa were discovered. Cocoa is high in bitter-tasting flavinoids, which are the prime source of such antioxidants but which many chocolate manufacturers extract to improve taste.
However, there are no labelling requirements to inform the consumer of this. Sugar, which can lessen the benefits of cocoa, is also often added to improve palatability. Hence, while genuine dark chocolate has health benefits, chocolate that is simply labelled ”dark” does not necessarily have these benefits.
Exercise is better than dieting for weight loss – FALSE
It is easier to reduce energy intake by a given amount than to increase energy expenditure by the same amount. Reducing intake by 1000 calories a day, for example, is the equivalent of walking an extra 15 kilometres daily. For this reason, dieting is more likely to be successful in the early stages of a weight-loss program. But exercise is important in weight loss and it may be more important than dieting in the maintenance stage, after effective weight loss. And both psychological and physiological factors must be considered, in which case neither exercise nor dieting is better than the other.
A low-protein diet is best for weight loss – FALSE
The success of a weight-loss diet depends mainly on the total calories. Specific nutrients generally make little difference but some have advantages. Protein can increase the sensation of fullness, particularly in comparison to sugary, starchy carbohydrate foods. In the context of the modern high-calorie diet, a reasonable intake of protein is likely to be better for weight loss than a low-protein diet.
The present protein intake of about 13 to 15 per cent of total energy is well below the estimated 25 to 30 per cent often proposed for weight loss and a healthy diet.
Fat people don’t get more hungry than lean people – TRUE
It is difficult to evaluate a subjective feeling such as hunger among individuals, but research indicates hunger is not a distinguishing factor in obesity. Much overeating has a psychological and environmental, rather than physiological, basis and hence there is little reason to believe in a difference in genuine hunger – as distinct from psychologically conditioned ”appetite” – between slim and overweight people.
Swimming is better than walking for weight loss – FALSE
In general, the best exercises for weight loss are those that are weight-bearing, such as walking or jogging. Up to 30 per cent less energy is used in activities such as swimming or cycling, which support weight and can be carried out at a more leisurely pace.
Because fat floats, an obese individual is likely to use relatively less energy while swimming, particularly if that person is an experienced swimmer. This does not negate the benefits of swimming as an exercise but reduces its relative effectiveness for fat loss compared with walking.
Weight lifting is good for fat loss – TRUE
In general, any form of exercise involving energy expenditure has benefit for weight loss. Resistance training is often underrated and considered only for the development of strength or size. However, where large muscles or muscle groups are used – or in resistance training using light weights at high repetitions – weight lifting can be effective for weight loss as well as muscle strengthening.
The best measure of body fat is body mass index -FALSE
Body mass index – a ratio of weight to height – does not correlate well with fatness in individuals. Body mass index is less accurate in people with a more muscular body type, some ethnic groups such as Pacific Islanders, and the elderly, whose height shrinks with age. This can lead to unrealistic goal weights. Waist circumference and some other body measures, or bioimpedance analysis, provide better estimates of body fat.
You lose more weight doing exercise you are good at – FALSE
Individuals become more efficient and expend less energy as they become experienced with a particular form of exercise. A fit, experienced runner, for example, requires less energy to cover a set distance than an unfit individual of the same weight, age and gender. Weight loss requires excess energy expenditure, which comes more from activities with which an individual is not so familiar.
An obese person can be fit and healthy – TRUE
While fitness and fatness are usually inversely linked, studies have shown that many active individuals can maintain good health irrespective of body weight. There is also accumulating evidence that a significant proportion of obese individuals do not suffer the damaging metabolic effects from their extra weight that might be expected, while a significant proportion of lean individuals do suffer such health problems. This has led to new questions about the effects of obesity as a marker, rather than a cause, of disease.
Garry Egger is Adjunct Professor of Health and Applied Sciences, Southern Cross University. Sam Egger is a statistician at the Cancer Council NSW.
Article Via SMH.com