Positive Health Online

The "global epidemic" as the World Health Organisation describes the increasing rate of obesity (WHO, 1997) shows no signs of slowing down. Modern technology provides ever more sources of information about healthy eating – computer programmes to help you calculate the nutritional content of all foods, low-fat cookery programmes on television, books and magazine articles full of sensible advice – but the latest figures show the number of people who are overweight and obese continues to rise in Britain as in every other country. Meanwhile the costs of obesity to the individual and to the state are reiterated in the media constantly by the medical profession. Doctors have known about the risks to health of being overweight for centuries; Hippocrates (460-377 BC) noted that stout people were more likely to die suddenly and unexpectedly. These observations have been confirmed and extended; many studies have shown that obesity is a major risk for heart disease, stroke, type II diabetes, many types of cancer, infertility and lung disease (see e.g. Manson et al. 1995). People have been trying out different methods of reducing weight for centuries, too, and this article aims to give an overview of these.

There was dismay when it was found people desperate to lose weight were being cynically exploited by unscrupulous salesmen on the Internet advertising soaps guaranteed to "wash fat away". However, eating soap was an early medical treatment, and an Edinburgh doctor reported some success with this treatment in the eighteenth century. Weight loss treatments then as now were worth money to those who provided them; billions are now spent on slimming foods and products worldwide, and billions more on drug developments. Pills to help you slim have been sold for hundreds of years, with the most appalling ingredients, including strychnine, camphor, digitalis, and arsenic. These were supposed to act as purgatives, in that they were laxatives or made you sick, or were said to have magic anti-fat properties (which they didn't) or that they could suppress appetite (which they couldn't). The list of food items, supplements, herbs, animal derivatives, and combinations of all of these promoted as weight loss agents would fill many pages. However, the same ingredients are re-packaged and sold as a new product year after year, and I will describe some of the most common used in weight control products.

High-fibre supplements and bulkers

High-fibre supplements work on the premise that they fill you up so much before a meal that you don't feel so hungry and therefore eat less when you do eat; these generally contain bran, pectin, fibre and/or vegetable extracts. It is also sometimes claimed that eating a lot of fibre reduces absorption of energy from the gut. Scientific investigation on the role of fibre in stopping you feeling hungry while you are eating (called satiation) and reducing how much you eat at a later meal (called satiety) has been carried out. In experiments two groups of people were given meals of the same calorie content, but for one group they were high and for the other low in fibre. How much both groups ate then immediately after the meal, how much they ate later, and how full they said they felt was measured. The people on the high fibre meal (10gm or so) said they felt fuller, but in fact both groups ate the same amount! There isn't any scientific evidence that eating fibre before a meal actually reduces the amount you eat at the meal.

Other substances called bulkers swell up in the stomach, as bran does, and this is supposed to reduce appetite. One bulking agent used is guar gum, which may be described as cyamopsis tertraglobula or as cyamopsis psoraloides. Guar gum has been shown to make people both feel less hungry and eat less. However, this was in quantities much greater than permitted under British law; after reports of the lethal possibilities of gums their level was restricted to 15% of any tablet or supplement (in some cases the gums swelled up in people's mouths, before getting to the stomach, and the poor unfortunates were asphyxiated).

Starch blockers

Fifty years ago it was theorised that wheat and kidney beans could reduce the absorption of starch through inhibition of an enzyme, amylase. The purified ingredient was extracted from the kidney bean, Phaseolus vulgaris, and named Phaseolamin in 1975. Billions of starch-blocker pills were consumed by people in the USA in the 1980s, believing that these would allow undigested starch to pass through the bowel, thus reducing the calorific effect of any starch foods eaten. Research proved conclusively that starch blockers were completely ineffective when taken by mouth – as measured by the amounts of calories in faeces after taking a high-starch meal and starch-blocker pills or a placebo, or by blood tests.

Amino acid pills

Amino-acids such as arginine, lysine, ornithine and phenylalanine are essential to body processes concerned with the breakdown of food, including fat, and are often included in slimming products. But a study of an ornithine/arginine pill compared with other methods of weight loss found that a "pretend" diet – eating half a carrot before meals – was just as effective. There's no evidence that taken in capsules or tablets amino-acids have any effect on anything at all, and the United States Food and Drug Administration banned them from being included in over the counter diet products, because the manufacturers couldn't prove that they worked.

Seaweed tablets

Seaweed tablets made from kelp or the brown seaweed Fucus vesiculosus contain iodine. Iodine is used to make thyroxine, the thyroid hormone which regulates metabolism. The first use of iodine as a treatment for obesity took place over 100 years ago, but kelp tablets have not been shown to have any effect on metabolism. Only in people with an iodine deficiency (and there are very few of them) do iodine supplements increase the production of thyroxin and so increase metabolism.

Diuretics

Some tablets contain diuretics, from natural sources, which will make you urinate more and apparently lose weight. These include all sorts of natural herbs, extracts and oils. Dandelion is a well-known diuretic – it's old English name was "piss in bed", although recent scientific research shows no strong diuretic effect.

Fennel was thought by the Ancient Greeks to help in slimming, and does act as a diuretic. Hydrangea, orange peel, meadowsweet, bearberry, pokeberry, horsetail and juniper are also believed by herbalists to either irritate the bowel, with a laxative effect, or act as a diuretic.

Guarana

From South America comes guarana, which is described as a stimulant; it doesn't have any more effect on slimming than drinking coffee would, for the very simple reason that it's almost completely composed of caffeine. However, every year there is a crop of new straight-from-the-jungles-of-somewhere-exotic, just-discovered miracle plant extracts which make you lose 5 pounds overnight without dieting or exercising and are only £39.99 for a small bottle of useless pills: beware.

Lecithin

Many tablets contain lecithin from soya oil, which is used as an emulsifier to make the tablets smooth. It is sometimes suggested that lecithin has some sort of fat-burning qualities as well. It will not decrease fat absorption. It has no known effect on metabolism or on fat-burning when taken in this form.

Herbal teas

Although claims have been made for various teas, made from kombucha, Chinese herbs or whatever, there is no scientific evidence that they are effective in promoting weight loss either. Recent work on chitosan, claimed to be a "miracle fibre" and the main ingredient in a new variety of slimming pills sold over the counter, shows it does not absorb ingested fat and does not aid weight loss; not very surprising, since there's no physiological reason why eating ground up sea shells (which is what it is) should have effects on human digestion.

However, we all know people who will swear that they did lose weight on some esoteric extract of weeds. How can this be, if there's no evidence of actual scientific proof? Many of these products suggest you follow a reduced-fat or reduced-carbohydrate diet while taking the product, or insist that strange combinations of unusual foods be eaten. This will generally result in a lower calorie intake, and it is the reduced calorie intake which leads to the weight loss, not the weight loss product.

What pills and potions do work, then?

Not until ephedrine was discovered in the late 19th Century was an effective agent to increase metabolic rate found, and would-be slimmers drank copious quantities of it in tea. The study of how ephedrine worked led to the development of amphetamines in the 1930s and eventually to the new drugs used today, which act on the central nervous system to reduce appetite. These drugs are only available on prescription, and only for a limited period of time, under medical supervision, to the seriously obese. However, two of these, which had been shown to aid weight loss – Adifax and Ponderax – were last year removed from the list of permitted drugs; they had been shown to have caused long-term damage to heart tissue in some patients. However, Orlistat, marketed as Xenical, was approved last year. It is a gastric and pancreatic lipase inhibitor. It has been found that 30% of the fat eaten in the diet will be excreted in the faeces when the drug is taken. However, the drug will only be prescribed to those of Britain's 8 million obese persons if they agree to lose at least 2.5 kg in the month before starting the programme of exercise and calorie control with which they must comply while they are taking the drug, or it will be withdrawn. In trials, those taking the drug for two years lost an average of about 8 kg; but half of this weight loss was accounted for by the reduced calorie diet. A very unpleasant side effect of eating large amounts of fat while taking the drug is faecal incontinence, and it is thought fear of this consequence contributed to people's sticking to the reduced fat diet (Garrow, 1998).

Famous diets

Doctors have been profitably sharing their views about weight loss treatments ever since Professor Yudkin published his immensely successful book This Slimming Business 40 years ago. Nutritional advice about weight loss has changed since 1958 – he advocated cutting down on all carbohydrates – bread, cakes and pasta – while eating plenty of cream, cheese, butter, meat and fish!

Dr Hay didn't live long enough to benefit from the huge sums of money created by the Hay System and its spin-offs. He believed that ill health resulted from the accumulation of toxic wastes in the body, partly caused by mixing starches with protein in the same meal, and thus not providing the alkaline environment he considered essential to good digestion. Everything we eat, according to the theory, is either acid-or alkaline-forming. Acid-forming foods (e.g. meat, cereals) should be cut down, and the intake of alkaline forming foods (e.g. fruit, vegetables) increased. In any case you shouldn't mix the two kinds of food together. Dr Hay's ideas about food combining are entirely without scientific proof. If eating eggs and bacon together was as bad as he suggest it's a wonder the human race has survived. Try telling the millions of poor people all over the world who live on a diet of vegetables and rice, whose parents and grand parents did so, that their diet is making them fat.

Then came Dr Herman Tarnower's Scarsdale Diet. Dr Tarnower was a physician specialising in heart disease in private practice who developed his diet for his own patients. His is said to be the world's best-selling diet book ever. The diet is a high protein, low fat and low carbohydrate one. No alcoholic drinks are allowed nor oils or fats; meat must be lean, and you should stop eating when you are full. Dr Tarnower wasn't much of an advertisement for his diet – he was always a stone overweight himself, according to his own charts – but this diet has been in and out of favour in different forms ever since he devised it.

The contradictions between all these eminent doctors' views still persist among experts. For example, a recent book claimed that dieters shouldn't cut out sugar – "eat chocolates and still lose weight" – (System S, by Sally Ann Voak and Professor Anne de Looy) while another stated that sugar is worse for you than fat (Sugar Busters!(tm) Cut Sugar to Trim Fat, by H. Leighton Steward et al). How are people to decide between these competing claims?

How to lose weight

There's no evidence that eating a low carbohydrate or a high carbohydrate diet or a high sugar or low sugar one or a high protein or low protein one is going to make any difference to the amount of weight lost on a diet (although it might to your overall health). All that matters is the calorific content of the diet. As a very rough guide your basal metabolic rate, which determines how much food you need to keep going at the weight you are, if you are just lying in bed all day, is about 1/2 a calorie per kilo of body weight per hour. So if you weigh 140 lbs you will use up approximately 70 calories an hour, 1680 calories per day doing nothing except living. If you weigh 14 stones, you will need 2352 calories per day to keep on going at that weight.

In the real world we all have to get up, and BMR accounts for only about 60-70 per cent of energy expenditure. Another 10% or so is taken up by what is called the thermic effects of food, or diet-induced thermogenesis. On a daily requirement for the average woman, it is only about 190 calories, and eating your food cold, three times a day, as breakfast, or six meals, with coffee or doused with chilli won't make any difference.

The last component of total energy expenditure is the amount of exercise taken – not as aerobics or swimming necessarily but just the total level of physical activity, which could be knitting, taking the dog out, or bathing the children. This, of course, varies from person to person.

There is no doubt that exercise causes you to expend energy, and the more vigorously you exercise, the more energy you expend. So while gentle walking uses up only 100 calories per hour, only a little more than lying in bed at approximately 70 per hour, really brisk walking could use up 400 calories per hour.

Another way to calculate how many calories you eat at present uses the metric system. For a man, calculate the resting metabolic rate (RMR) as 900 + 10 times (wt in kilos) and for a woman, 700 + 7 times (wt in kilos). Then multiply this estimate of the resting metabolic rate by 1.2, 1.4 or 1.8, depending on whether your lifestyle is very sedentary, moderately active or very active. This gives a rough estimate of your current intake.

Now, to lose a pound in weight you have to eat 3,500 calories fewer than you normally do, over a period of time. So if you ate 10 calories fewer per day you'd lose a pound in a year or so. It seems strange such a small amount can make a difference – but that's the way weight is put on; a small excess of intake over output is the reason most people gain about a pound in weight each year after 21. If you ate 500 calories a day fewer, you'd lose a pound a week. Most calorie controlled diets recommend eating between 1000 and 1800 calories per day, which for most people would result in a weight loss of 1–2 pounds per week, the medically advised rate of weight loss.

Of course, although there's no evidence you are more likely to lose weight on a diet containing more carbohydrate than on one containing less, there's some evidence that it's easier to stick to a diet with more carbohydrate. Carbohydrate itself may produce feelings of fullness earlier, or the fact that the food itself is more bulky might affect appetite; or carbohydrate rich diets may be cheaper, or more palatable.

However, there is now evidence which supports dieters' anecdotal reports of mood changes – "low fat rage" – consequent on the adoption of low fat diets. British researchers have shown that when half of a group of healthy men and women were changed to a diet containing 25% instead of 41% fat they were rated as more angry and hostile than the group who remained in the 41% fat diet. It's possible these feelings of anger could lead to people being less likely to continue with a low-fat diet. And it's the question of sticking to a diet that is the paramount one; the best advice is to find one that suits you and your life style. Diets work if calories are reduced; there are no magic ingredients which cause weight loss.

In fact, there's no magic. There just isn't. If you want to lose weight you have to eat less; and once you've lost weight, you have to keep on eating less. If you go back to your old ways of eating you will put on weight again. And that, unfortunately, is what happens to most people who lose weight successfully. Only a permanent change in lifestyle can assure a permanent change in weight.

References

Manson et al (1995) Body Weight And Mortality Among Women. New England Journal of Medicine, 333, 677-685.
Wells et al (1998) Alterations In Mood After Changing To A Low Fat Diet. British Journal of Nutrition, 79, 23-30.
WHO (1997) Obesity: preventing and managing the global epidemic. Geneva, WHO.
Garrow, J. (1998) Flushing away the fat. BMJ, 317: 830-831