Tuesday, 12 October 2010

The truth about diet pills

reposted from:

We all want a quick fix for our weight problems. But are slimming pills really the answer?
Dr Porter’s verdict: Alli has proved disappointing; Capsiplex: the four clinical studies on this diet aid are too small, and too short, to be taken seriously; Slimweight patch: pseudoscience at its best
An effective slimming pill has been the holy grail of the pharmaceutical industry for decades, but despite spending billions of pounds on the quest, it has proved elusive. Most of the drugs developed over the past 40 years have been withdrawn, and few doctors rate the only licensed version still available in the UK (orlistat, which works by impairing absorption of fat). So why are pharmacists, health-food shops and online retailers doing such a brisk trade in over-the-counter slimming aids?
I wish I could report that the nutriceutical industry had pipped the pharma giants to the post, but the truth is far more mundane and the fact that people in the UK spend an estimated £75 million a year on this type of slimming pill simply reflects a triumph of marketing over common sense. The wilder the claim, the more popular the product seems to be. Capsiplex — available online and from high street chemists and health-food shops — is a case in point. It uses a “proprietary patented matrix of excipients and coatings” to deliver capsicum extract, which the manufacturers claim will boost your energy levels and help you to “burn 12 times more calories”. All for the sum of £29.99 for a month’s supply, although price wouldn’t seem to be an issue as suppliers were reported to have sold out within three days of the UK launch earlier this year.
Or how about the Slimweight patch (available online) that uses “transdermal technology ... previously found only in science fiction” to deliver a mix of ingredients, including seaweed and guarana, to help you to effortlessly lose up to 4lb a week? Yours for only £19.86 a month.
What nutriceutical slimming aids such as Capsiplex and Slimweight have in common is that they are based on some real science. Capsicum extract — the natural ingredient that gives chillies and peppers their kick — has been shown by researchers to boost the body’s metabolism temporarily, but that doesn’t necessarily translate into useful benefits in the real world, or in the longer term.
The four clinical studies trumpeted on Capsiplex are too small, and too short, to be taken seriously. The largest to be listed on the website monitored 14 volunteers over two weeks, the smallest followed only six subjects over eight days.
Suffice to say that I could not find any quality research suggesting that Capsiplex has anywhere near the potential to meet the promise on the website that “now you can lose all the weight you want and keep it off”. And I will happily eat my words if such evidence does exist, along with the entire Saturday edition of The Times in which it appears.
The Slimweight patch stretches its scientific credentials even farther. By bombarding prospective purchasers with references to cutting-edge patch technology that results in “no side-effects due to transdermal admission methods”, the manufacturers seem to be hoping that they will be so impressed that they won’t notice the dearth of decent data to back up the slimming claims. Pseudoscience at its best.
It seems unfair to mention orlistat (Alli), the only fully licensed slimming aid, in the same breath as nutriceuticals, but it is flawed too. It may have taken more than a decade of research and development to bring to market, and gained the blessing of the National Institute for Health and Clinical Excellence, but my experiences suggest that it’s not all it’s been cracked up to be.
Orlistat works by blocking the action of enzymes in the bowel — lipases — that break down fats into their constituent components so that they can be more easily absorbed. The net result is a significant reduction in fat absorption with about 25 per cent to 35 per cent of the fat content of a meal that would otherwise have been absorbed passing straight through the bowel, significantly reducing a person’s calorie intake.
Not surprisingly, when combined with a sensible diet and exercise programme, there is good evidence that orlistat speeds up weight loss. Overweight volunteers taking the prescription-only dose (120mg versus the 60mg in over-the-counter Alli) have been shown to lose 2-5kg (4-11 lb) more over a 12-month period than those given dummy versions of the drug.
But, away from the controlled environment of clinical trials, orlistat has proved a disappointment. While it may accelerate short-term weight loss, it doesn’t work in the longer term — most of my patients using it have failed to get anywhere near their target weight, or ended up even heavier after stopping the drug. And there is now a dawning realisation among doctors that surgery (such as gastric banding) is the only truly effective medical intervention for tackling obesity — which is a sad indictment of the profession, the individual and society.
Even if the pharmaceutical industry does find its holy grail — and there are contenders in the pipeline with modes of action ranging from tricking the brain into thinking that the stomach is full, to making eating less enjoyable by impairing smell and taste — slimming drugs are only ever likely to be a useful tool for getting people down to a healthy weight in the short term. The difficult part is keeping them there, and that requires a profound and sustainable change in their diet and lifestyle (the reason, of course, why they were fat in the first place).
Pills are all very well, but unless you take them for ever they strike me as part of the problem rather than the solution.
How can taking a short-term slimming aid help unless it is accompanied by long-term dietary and lifestyle change? Or, to put it another way, could slimming pills make matters worse by encouraging overweight people to have their cake and eat it

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