At any given time, as much as 50 per cent of the population is on a diet. Yet, surveys show that we are getting fatter, not leaner.

No one could deny that taking an appetite suppressant to lose weight is the fast track to nowhere. Recent health scares related to heart and respiratory problems linked to the conventional diet pills fenfluramine and dexfenfluramine led to their voluntary withdrawal from the market in 1998.

In the wake of this, there was a renewed interest in ‘natural’ alternatives, particularly those which claim to boost metabolism.

Among supplements, the most well-known thermogenic is ma huang (Ephedra sinica), the active ingredient of which is ephedrine. This herb has been shown in several trials to help the body burn up fuel faster (Aliment Pharmacol Ther, 1991; 5: 413-8; Int J Obes, 1982; 6: 343-50).

Other studies suggest that the effects of Ephedra can be enhanced when used with other stimulants such as caffeine and theophylline (Am J Physiol, 1987; 252: R507-13; Int J Obes, 1986; 10: 467-81) and with salicylates (Am J Clin Nutr, 1987; 45: 564-9). Indeed, many alternative medicine handbooks uncritically list this supplement as the best way to speed up the metabolism.

But ephedrine (which is only available on prescription in the UK) should be taken with some caution. As its popularity has increased (and with it, the number of reported side-effects), it has become the subject of intense debate, especially in the US where it is still
available as an over-the-counter supplement. Ephedrine can be effective under some circumstances. In one study, it was compared with dexfenfluramine - the participants taking ephedrine lost more weight, but complained of more adverse effects (Int J Obes Relat Metab Disord, 1994; 18: 99-103) - though these were shortlived.

To date, the FDA reports that 273 individuals have either been sickened or have died as a result of taking ephedrine-containing products. The number may seem small in relation to the number of individuals who may be taking these products. But the fact that such adverse reactions have been reported at all (when most GPs are notorious for underreporting drug reactions) suggests that many more may be experiencing mild-to-moderate adverse reactions without their being reported.

Overuse can lead to heart palpitations, nausea, irritability and, according to recent evidence, the formation of kidney stones (Am J Kidney Dis, 1998; 32: 153-9). Ephedrine has many contraindications, and those who have heart, blood pressure, thyroid or prostate problems, or who have diabetes or are on antidepressants should not take products containing ephedrine. It is best taken under the supervision of a therapist and perhaps best reserved, and most effective, for those who are very obese.

No industry preys on people's fears and insecurities about their bodies as much as the diet industry. In the natural-health sector, there are hundreds of products which typically promise to help you burn fat, increase the rate of your metabolism and control your appetite - sometimes all in the same pill. One survey into the advertising of nutritional supplements in health and body-building magazines counted 89 brands, 311 products and 235 unique ingredients (most frequently unspecified amino acids). More than 20 per cent of the products advertised listed no ingredients at all (JAMA, 1992; 268: 1008-11).

The question is how many of these actually work and what level of satisfaction can you expect if you take them?

A recent study into the effectiveness of non-prescription weight-loss supplements was revealing. It concluded that there was no good evidence for any weight-loss benefits with most of the products reviewed by the researchers (Med J Aust, 1999; 171: 604-8).

Similar studies into the claims for body-building and weight-loss supplements aimed at athletes showed a similar lack of efficacy and little basis in scientific evidence (Sports Med, 1993; 15: 90-103; Ann Pharmacother, 1993; 27: 607-15). Another review was similarly scathing about the lack of data on dietary supplements such as chromium, creatine, and certain vitamins and their role in weight loss (Phys Med Rehabil Clin N Am, 1999; 10: 673-703).

We decided to find out if there is any evidence for the claims made by manufacturers of weight-loss supplements. We perused a selection of health magazines and leaflet displays in healthfood shops and selected, at random, a few products that claim to aid weight loss. PROOF! then carried out an investigation which included contacting their distributors for more information about the products.

Rating such products is an exercise in relativity. For the purposes of this feature, we awarded one star for those products that have published human studies to back up their claims. One star was given for those with anecdotal evidence to back up their claims, and one star for inclusion of ingredients that have a theoretical basis for their use. Although value for money takes into account whether or not the product actually works, we have also awarded one star for those products which appear to be reasonably priced.

It should be emphasised, however, that a high rating of four stars does not necessarily mean that the product is guaranteed to produce weight loss. Indeed, none of the products reviewed was categorically able to show that it could produce weight loss independent of a controlled diet and exercise regime.

THE PRODUCTS

Citrilean
Distributor: Higher Nature
Price: £17.99 for 90 tablets (6-week supply)
Rating: ****
Contains a standardised form of hydroxycitric acid (HCA), also known as tamarind or Garcinia cambogia. HCA does not appear to stimulate metabolism (Int J Obes Relat Metab Disord, 1999; 23: 867-73). Instead, it is thought to act by suppressing the appetite (Biochem J 1990; 272: 181-6; Fed Proc, 1985; 44: 139-44) and, in places where it is regularly used as a cooking ingredient, it is known to make food more ‘filling’ (Med Hypoth, 1988; 27: 39-40). Most of the trials were small and, when the supplement was subjected to a recent double-blind placebo-controlled study, no evidence was found in favour of HCA (JAMA, 1998; 280: 1596-600).

In the debate which followed the publication of this study, several practitioners protested that the study participants were on a high-fibre diet and that this probably interfered with the intestinal absorption of HCA (JAMA, 1999; 282: 233-5). We could find no evidence to support this. In fact, additional fluid and fibre intake appears to heighten the effects of HCA, while a high-fat diet and high levels of alcohol consumption (more than two glasses of wine or two bottles of beer per day) will interfere with them.

There is no optimal dose for HCA, although success has been achieved by taking between 800 and 1500 mg daily (JAMA, 1998; 280: 1596-1600). Different individuals may require different doses.

The best we can say for HCA is that it appears to be non-toxic and may work for some individuals, but only as part of a regime which includes reduced calorie intake and regular exercise. Its price per tablet is about 20 p (or 40 p per day), making it relatively good value.


Reshape
Distributor: Reflex
Price: £39.99 for a 28-day supply
Rating: **
Reshape is an amino-acid and mineral combination containing L-carnitine, hydroxycitric acid, chromium chelate and magnesium chelate. Amino acids and minerals are a popular combination in many slimming products. Since our own diets are so mineral- and amino acid-poor, some individuals may well respond to such supplements.

But here's the problem: most of the trials of amino acids like L-carnitine have been carried out on healthy, active, athletic types. By their very nature, these individuals will be eating a better diet than most of us and burning more calories each day. Among this population, L-carnitine has been shown to improve stamina and to help build lean body mass. But this does not mean that it will act this way in a sedentary obese person.

There are also a number of clinical trials on some of the ingredients, particularly hydroxycitric acid (see information under Citrilean, page 3) and chromium, some of which show that they can assist weight loss but, again, these are often in specific subgroups of the population. Chromium, for instance, can aid glucose control in diabetics, but studies into its effects in non-diabetic obese individuals have mixed findings (Acta Med Aust, 1997; 24: 185-7; Nutr Rev, 1998; 56: 266-70; J Sports Med Phys Fitness, 1995; 35: 273-80).

This product is a powder which is mixed into water and taken three times daily. Taken as directed, it will give a very high dose of each supplement. Certainly, its distributor Reflex deserves full marks for full disclosure in their advertising of what is in the product and how much you will get per dose. Very few companies do this.

However, questions such as whether a combination is better than the single supplement still remain. The answer is: nobody knows.

Reshape contains no stimulants and is likely to be safe to use over the longer term. But, at 48 p per serving (£1.43 per day), it is pretty expensive. It is available from healthfood stores and gyms, and by mailorder on 01273 297 295 or from their website (www.reflex-nutrition.com).


LipoTone
Manufacturer: BioCare
Price: £44.95 for 28-day supply; £9.25 for 60 maintenance capsules
Rating: ***
LipoTone's main ingredient is conjugated linoleic acid, or CLA (a relative of linoleic acid). While relatively new to the UK, CLA has been a mainstay of slimming supplements in the US for several years. This naturally occurring fatty acid is found in ruminants such as sheep and cows (cud-chewing animals; CLA is produced by the normal bacterial flora in their gut) as well as in turkeys and dairy products (not the low-fat variety), and is involved in the efficient transportation, storage and metabolism of fats in the body.

The majority of the research into CLA has been focused on its anticancer properties (in the lab and in animals). However, recently, the focus has shifted to its potential for increasing lean tissue mass while reducing fatty tissue storage. In fact, CLA is the only animal fat with these properties. Research in this field is still in its infancy (Curr Opin Clin Nutr Metab Care, 1999; 2: 499-506) and, in some ways, the product has become widely available in advance of long-term studies and conclusive published data in humans.

Plants also contain small amounts of CLA. LipoTone's CLA is derived from sunflower and safflower plants, and is GMO-free. In addition to CLA, the LipoTone powder also contains L-carnitine, potassium and hydroxycitric acid - supplements which may aid weight loss in some individuals.

A review in the Journal of Chemical Education (1996, 73: A302) suggested that CLA derived from plants is different from CLA found in animals and may be less biologically active, but this appears to be due to differences in the manufacture of plant-derived CLA. In the case of LipoTone, the manufacturer claims that the CLA is identical to that found naturally in animals.

We have seen data which does indeed indicate that CLA can improve the fat-to-lean ratio - but, thus far, only in rats (J Nutr, 2000; 130: 1140-6). Human studies so far have concentrated on the ability of CLA to build muscle and improve stamina in body-builders and weight-trainers, but these results may not truly reflect the results which might occur in an ordinary person’s body (J Strength Cond Res, 1998, 11: 280; Med Sci Sports Exer, 1998; 30: S182).

There are a lot of ironies attached to this product. A dieter might need to take it because of nutritional deficiencies caused by years of stringent dieting. Even those of us not seeking to lose weight may be deficient in CLA because of our modern-day lifestyles.

Having said this, the idea that we are deficient in CLA seems to have originated (as far as we can see) from the US manufacturers of the supplement. There is no recommended daily allowance for CLA and, therefore, no official definition of a minimum daily amount that humans need to achieve a basic level of health.

With the right microorganisms in their gut, non-ruminant animals such as rats can synthesise linoleic acid into CLA. It is thought that humans can too (Am J Clin Nutr, 1998; 67: 332-7), but only those who maintain an excellent diet, a health-supportive lifestyle and a good balance of gastrointestinal flora - and how many of us meet all three criteria?

This is potentially a useful supplement, but watch out for the marketing men. There is already talk of fortifying farm animal food, dairy products and prepackaged low-fat foods with CLA so that they can be marketed as healthy alternatives - probably with a high price tag. At £1.61 per one-a-day sachet, LipoTone is one of the most expensive products we reviewed.


Fat Magnets
Distributor: Swiss Health
Price: £19.95 for 100 capsules (one-month supply)
Rating: **
This product is one of many made from chitosan, the fibre in crushed shellfish shells. The advertising leaflet, which can be picked up in healthfood shops, also claims that the product has a positive ionic charge, and it is this positive charge which attracts negatively charged fat.

There is at least some theoretical basis for products containing chitosan. Unfortunately, most of the evidence for its efficacy is based on studies with rats. The only human clinical trial we could find suggested that chitosan on its own did not help reduce body weight (Eur J Clin Nutr, 1999; 53: 379-81) - thus, it is impossible to say whether chitosan can act on its own to encourage weight loss independent of a calorie-controlled diet. Odds are that it can't.

There's also the concern, as with all fat-binding products, that the fat-soluble vitamins (A, D, E and K) will also be removed from the body when using it. Taking it with EFA supplements may also negate the effects of EFA since it may theoretically bind with good fats as well as bad.

The information about the positive ionic charge is somewhat confusing. Most data suggest that a negative charge - such as in the water we drink - is healthgiving, while a positive charge promotes disease. We could find no evidence that a positive charge attracts fat like a magnet. What's more, the information which we received from the distributors contradicted the published literature, saying that chitosan was negatively charged and attracted the positively charged fat like a magnet. There is, in fact, little scientific evidence either way, but the inconsistency with popular perceptions gives pause for thought.

Fat Magnets are available at Safeway, Superdrug, Harrods and Selfridges, and will cost you just under 20 p per capsule (approximately 60 p per day), which is reasonable.


Ultra Diet Pep 2000
Distributor: Capital Cliff Ltd
Price: £20.95 for 60 capsules (30-day supply)
Rating: **
Ultra Diet Pep 2000 is a long-established American over-the-counter diet aid. Although it contains HCA (375 mg per tablet) and an assortment of amino acids, B vitamins and chromium, it is primarily a herbal stimulant.

The main ingredients are in a herbal base which includes kola nut, guarana, Siberian ginseng, wild yam powder, dandelion root, kelp, passion flower, gotu kola and liquorice.

Apart from the HCA, there is little in this blend which has evidence of guaranteeing weight loss. It probably won’t work in the absence of a calorie-controlled diet.

Its price per capsule works out at 35 p, or 70 p per day, which most people would consider reasonable.

7-Keto Naturalean
Distributor: Enzymatic Therapy Natural Medicine
Price: £36.95 for 30 capsules (two-week supply)
Rating: **
The active ingredient in this supplement is 7-keto DHEA, a naturally occurring metabolite of DHEA which has no known hormonal effect on the body. Instead, says the manufacturer, it boosts metabolism and supports optimal thyroid function.

The other ingredients which make up the mixture are amino acids (L-tyrosine, choline, inositol), minerals (copper, manganese, iodine) and asparagus root extract.

7-Keto DHEA is also relatively new in the UK. However, in the US, it is being hailed as the “ultimate DHEA”, a new wonder supplement used to treat a staggering variety of health problems, including Parkinson's disease, chronic fatigue syndrome, ‘stress’, migraines, sagging libido, flabby muscles, diabetes, osteoporosis and, of course, obesity.

Research conducted by the man credited with its discovery, Dr Henry Lardy at the University of Wisconsin, reports, not so surprisingly, many positive effects, including improved thyroid function and greater thermogenesis (Proc Natl Acad Sci, 1995; 92: 6617-9; Arch Biochem Biophys, 1997; 341: 122-8; Steroids, 1998; 63: 158-65).

These claims, unfortunately, were based on rat studies. We found some evidence that 7-keto DHEA combined with one hour of cross-training three times a week could yield a significant weight loss - more than three times that of the exercise/placebo group - over an eight-week period (J Exer Physiol [online], 1999; 2(4); ISSN 1097-9751).

Once again, we have a product which promises results in people which have primarily been found only in lab rats and in a limited segment of the population which has enough energy to do cross-country running three times a week.

Don’t expect miracles and also be aware: while it is thought to have no hormonal effects, some of the other 7-keto DHEA products we found contained the caution that 7-keto DHEA can sometimes cause breast enlargement - is there something that we are not being told?

This was the most expensive product in the review, costing a whopping £1.23 per capsule, or £2.46 per day.


Bonsal
Distributor: Nashi Pharmacy
Price: £19.99 for 60 capsules (two-week supply)
Rating: *
Bonsal announced itself on the pages of a health magazine with the questions “Have you ever wondered why sea animals never get fat?” Apart from the fact that many sea animals depend on fat to survive the extreme cold of the water, this was not a question we had ever considered.

When we phoned the information number, the representative for Bonsal was unable to tell us what the product was exactly, only that it was “made from shellfish”. Between the distributors and the advertising for the product, we have gleaned that, once in the body, Bonsal is supposed to function like a sponge to soak up the fat from your food and take it out of the body before it has a chance to be digested.

It all sounds fairly outrageous and maybe even dangerous. After all, we need some fat to live and the implication of such advertising is that you can eat what you like in any quantity you like, and Bonsal capsules, taken 10-15 minutes before each meal, will act as a kind of damage limitation. For something with only limited evidence and no guarantees, at around 33 p per capsule or £1.32 per day, Bonsal seems pretty pricey compared with other chitosan products. It is available at Superdrug and Lloyds.


Diet Phen
Distributor: Source Naturals
Price: £19.99 for 90 tablets (six-week supply)
Rating: **
The active ingredient in this product is the well-known amino acid and nervous system stimulant L-phenylalanine, which is most commonly found in aspartame. It also contains chromium and L-carnitine, both of which have a role in energy metabolism. The inclusion of St John's wort is a new twist which, according to the manufacturer, helps dieters by inducing a sense of ‘active calm’. The name is a direct reference to the (recently withdrawn) appetite suppressant fenfluramine - a ploy which suggests to dieters that it will work just as well as the conventional drug. Our concern is the combination of ingredients, which may exert a push-pull effect on the body. St John's wort stimulates the production of serotonin whereas L-phenylalanine blocks its formation.

Diet Phen also contains green tea extract, which may also boost metabolism (Arkopharma’s Phyto-Facts, 1989; 2: 2), cayenne, ginger and mustard seed as stimulants, and dandelion, which works as a diuretic, and chromium. Suggested use is one tablet to be taken 30 minutes before breakfast and lunch. Taking the product before dinner is not advised presumably because the level of stimulants in it will prevent sleep. There is no published research to show that this combination is effective.

The price per tablet is around 22 p, or 44 p per day.


AppleSlim
Distributor: Bional
Price: £8.95 for 40 one-a-day capsules
Rating: **
This simple formulation claims to help you absorb more energy from your food by keeping your digestive system healthy. It contains apple cider vinegar and vitamins E, B6, B12, folic acid, riboflavin and thiamine.

Apple cider vinegar has a long folk use, and is popular among naturopaths as a way of improving digestion and avoiding constipation. To our knowledge, there is no actual evidence that it does either although, once again, there may be some theoretical basis for the claim. Acids like apple cider vinegar act paradoxically in the body, helping to create a more alkaline environment in the gut. This favourable shift in the acid/alkali balance may help some individuals and may even work to even out cravings for certain foods. Who will benefit most, though, is unknown. It is recommended that users follow a low-calorie diet since the product is unlikely to produce weight loss without one.

The product itself has not been subjected to any research trials although, according to the technical department at Bional, it is due to be subjected to a clinical trial next year. Simple ingredients make for a cheap price - just over 22 p per one-a-day capsule - making AppleSlim the least expensive of all the products we reviewed.


Citrimax
Distributor: BioCare
Price: £20.10 for 90 capsules (30-day supply)
Rating: ****
Yet another hydroxycitric acid product, the potential benefits of HCA have already been explained (see Citrilean, page 3). Like all other HCA products, this one must be taken before meals so there is an inconvenience factor no matter who manufactures it. Each capsule contains 500 mg of HCA and 100 mcg of chromium.

Pricewise, Citrimax compares favourably with other HCA products at just over 22 p per capsule, or around 66 p per day.


Super Fat Burners
Distributor: Action Labs
Price: £14.95 for 60 capsules (2-week supply)
Rating: **
An amino-acid complex (aimed mostly at the athlete) with a twist. Included with the choline, L-carnitine, inositol and L-methionine are several herbs and other supplements such as corn silk, bromelain (from pineapple), Arctostaphylos uva-ursi and couch grass, all said to aid the thermogenic process. Chromium completes the mixture.

As we all know, our modern-day diets can be very poor and dieters, in particular, may skimp on protein from meat and so may be missing out on essential amino acids. You may feel better taking such a supplement, but there is no guarantee that you will lose weight.

Arctostaphylos uva-ursi (also known as bearberry), corn silk and couch grass have diuretic properties and will not aid the ‘thermogenic’ process.

Bromelain is an interesting addition. In sports medicine, it is used as an anti-inflammatory to reduce swelling due to injury or after surgery. When taken with food, it may be a useful digestive enzyme.

You are required to take this product four times a day at least 30 minutes before eating. The label recommends drinking 8-10 glasses of water per day while on the regime. The cost works out at 25 p per capsule or 10 p per day.


Chito-slimmer
Distributor: Healthcare Products Ltd
Price: £22.99 for 120 tablets (30-day supply)
Rating: **
As the name suggests, this is a fat absorber containing chitosan. We are still not convinced of its usefulness or even safety. Thus, we were glad to see some warnings on the label suggesting that this product, especially if used with other fibre supplements, can interfere with the absorption of some medications and should not be taken by those with gastrointestinal illnesses. The label also warns that the product will only work as part of a calorie-controlled diet.

The price is not bad at 19 p per tablet, or 76 p per day.

One question which arises from our survey is how these products get away with making such grand claims for their efficacy in their advertising. According to the Advertising Standards Authority (ASA), advertisements for slimming aids are fraught with problems - none the least of which is that it is aimed at a very vulnerable section of the population.

This has led to a specific subsection (51) in the British Codes of Advertising and Sales Promotion to deal with the advertising of slimming products. The code requires that 'any claims for the effectiveness or action of a slimming method or product should be backed up where appropriate by rigorous practical trials on people; testimonials that are not supported by trials do not constitute substantiation.' It also states that 'combining a diet with an unproven weight-loss method does not justify making slimming claims for the method.'

Just these two points alone are justification enough for reporting most of the products we have reviewed to the ASA.

In fact, the ASA has challenged several ads for slimming products over the years. In 1998, the ASA received 196 complaints about slimming ads, of which 59 (relating to 50 ads) were upheld. This is an improvement on 1997 figures when, of 107 complaints, 26 (relating to 26 ads) were upheld.

Unfortunately, the ASA can only monitor a limited number of publications and advertising leaflets each week, and many slip by unnoticed. Their own surveys into this field suggest that only around 60 per cent of slimming ads actually comply with the Code.

The truth is, every product will work for someone somewhere. The range of products on the market is truly staggering. Proof of their efficacy ranges from the bold-faced lie to the barely credible to the theoretically sound. Chances are, because such items are considered food supplements, whatever you take off the shelf will never have been subjected to any rigorous testing.

If anyone ever doubted that the health industry is the new religion, the slimming industry provides ample proof. Investing in such products often requires a substantial amount of faith over evidence. It also represents a kind of wish fulfilment, a belief in the magic bullet, and a reluctance to alter our lifestyles as well as our thinking about our bodies.

A tea made from the grapple plant (Harpagophytum procumbens, also known as Devil's claw) may help patients with metabolic problems, and also reduce cholesterol and neutral fat levels (see Josenhaus S et al., Ausserschulische Methoden bei Rheumatischen Erkrankungen, 1981; Heidelberg: E. Fischer Verlag). With supplements, look for those that are made only from the storage tubers and not the whole root, as only these preparations have been shown to be medicinally effective.

Exercise, of course, is not as easy to work into your life as a pill, but it is another well-proven way to boost metabolism. On its own, exercise may produce a smaller weight loss than a calorie-restricted diet. But this, say researchers, is compensated for by better weight maintenance in the longer term (J Am Diet Assoc, 1996; 96: 342-6). Many studies have shown that exercise is an important part of both weight reduction and maintenance after weight loss (Am J Clin Nutr, 1992; 56 [Suppl 1]: 190S-4S; South Med J, 1991; 84: 1470-4).

Food can be thermogenic, too The type of foods you choose can aid the thermogenic process. Studies show that carbohydrates have a greater thermogenic effect in the body than other foods (Ann Nutr Metab, 1984; 28: 245-52), though this response may be dulled in very obese subjects (Acta Diabetol Lat, 1989; 26: 155-62).

There is evidence that a high-carbohydrate diet can improve insulin sensitivity (Am J Clin Nutr, 1994; 59: 686S-9S), and insulin resistance is known to be a contributing factor to overweight in some individuals. Although the high-carbohydrate approach has mostly been used to help those with diabetes (Am J Clin Nutr, 1991; 54: 846-54), its use has been advocated in weight-loss regimes as well.

Unfortunately, not all carbohydrates are the same. While all eventually break down into sugar in the body, some do so more quickly than others, placing a burden on the pancreas to produce more and more insulin. Many are nothing more than simple sugars that create an enhanced insulin response in the body. Stick to a steady diet of these kinds of carbohydrates, and your pancreas can become exhausted and unable to produce enough insulin. Or your body may simply become insulin-resistant. While many of us now look for the hidden salt in foods, few of us are aware of the importance of monitoring hidden sugars as well.

The subtle differences in the way the body reacts to different carbohydrates was discovered 25 years ago when US scientists measured blood sugar after feeding human subjects a variety of foods. This research led to the development of the glycaemic index, or GI - a list of foods grouped according to how they affect blood sugar levels.

The GI index is widely used in the control of diabetes, but it has implications for weight control, too. Consumption of food with a high GI value may actually cause hormonal and metabolic changes that promote overeating in obese individuals (Pediatrics, 1999; 103: E26).

Professor Jennie Brand Miller, one of the co-authors of The Glucose Revolution (Hodder & Stoughton, 2000), has spent many years researching the GI index. She believes that carbohydrates are natural appetite suppressants and that, of all the carbohydrate foods, those with a low GI are the most filling and prevent hunger pangs for longer. In addition, she says, insulin not only regulates blood sugar, but is involved in how and where the body stores fat. By regulating insulin levels with low-GI foods, Brand theorises that this helps the body to burn fat more efficiently.

Her research has shown that even when the kilocalorie intake is the same, people who eat low-GI foods lose more weight than those eating high-GI foods. In her book, she quotes evidence from a South African study where participants were divided into low-GI and high-GI groups. The amount of calories, fat, protein, carbohydrate and fibre was the same for both groups - the only difference was the GI factor of their diets.

After 12 weeks, participants in the low-GI group had lost an average of 9 kg (20 pounds) - 2 kg (4 and a half pounds) more than those on a high-GI diet. Other evidence confirms the usefulness of using the GI to choose suitable carbohydrates for the diet of obese people (Nutr Rev, 1999; 57: 273-6).

Foods which produce a relatively low glycaemic response include legumes, pasta, barley, bulgur wheat, parboiled rice and wholegrain bread such as pumpernickel. Incorporating these foods into the diet has been associated with reduced blood glucose, insulin and lipid (fat) levels (World Rev Nutr Diet, 1990; 62: 120-85).

Some experts believe that obesity can be a response to accumulated toxins in the body. Many of the most harmful toxins, such as pesticides, are absorbed by the body and stored in fat.

According to Dr John Briffa, 'Toxins have an affinity for fat. They like to lodge themselves in the fat that is contained within the fat cells around the body. As a rule, the body does not like to let the concentration of potentially harmful substances rise too high. One way to reduce toxicity is to clear them more quickly. However, if this is not appropriate, or just doesn’t work quickly enough, the body's other option is to ‘dilute’ the toxins.'

Under these circumstances, fat becomes the body's storage system - a way of controlling and keeping these toxins from circulating to and damaging other parts of the body.

Dr Elson Haas, director of the Preventative Medicine Center of Marin County in San Rafael, CA, and author of Staying Healthy With Nutrition (Celestial Arts), concurs that obesity is almost always associated with toxicity and that any weight-loss regime should include measures to support the body as toxic chemicals are released. 'When we lose weight,' he comments, 'we reduce our fat and thereby our toxic load. However, during weight loss, we release more toxins and thus need protection through greater intake of water, fibre and the antioxidant nutrients such as vitamins C and E, beta-carotene, selenium and zinc.'

Another way in which the body attempts to dilute toxins is through the accumulation of water. Those who feel that their extra weight is the result of water retention may also benefit from a sensible detoxification programme.

Lowering the amount of fat in your diet may help to reduce your weight even if you do not lower the number of calories you consume each day (Am J Clin Nutr, 1998; 68: 1157-73), although evidence is mixed as to whether the low-fat diets or those which are simply calorie-restricted produce the best weight loss (Eur J Clin Nutr, 1995; 49: 79-90).

Certainly, a diet high in saturated fats tends to be less satisfying (J Am Diet Assoc, 1997; 97: S82-7; Int J Obes Relat Metab Disord, 1997; 21 [Suppl 3]: S2-11; Am J Clin Nutr, 1995; 61 [Suppl 4]: 960S-7S) and so may encourage overeating and yo-yo dieting.

According to fats expert Udo Erasmus, we need to change our views on fat in the diet, and we have to stop being fat-phobic. His experience is that those who take 45-70 mL of mixed fats (omega-3 and omega-6 fatty acids), the equivalent of 4-7 dessertspoons or 2-3 tablespoons, will consistently lose weight even if they don’t alter their diet.

He adds, however, that results will be better if EFAs are made part of a comprehensive diet regime including an increase in your intake of greens, cutting down on saturated fats, switching to organic foods wherever possible and supplementing with digestive enzymes.