The burning question

Yet another study has shown that the Atkins Diet works, but even the scientist in charge is baffled as to why the low-carb regime rduces fat more effectively than low-calorie eating plans. Robert Matthews reports

As an academic nutritionist at the University of Cincinnati, Dr Bonnie Brehm is at the cutting edge of research into the biggest question to hit her field in decades: does the Atkins diet work?

Most nutritionists faced with the torrent of anecdotal evidence for its effectiveness have simply parroted the mantra that more research is needed, while muttering darkly about possible long-term health effects. Dr Brehm and her colleagues, in contrast, have spent the past few years actually doing the research, and will unveil their findings at the American Dietetic Association's annual meeting next week.

They have been studying the effectiveness of the Atkins diet in scientific trials involving people classed as clinically obese, implying a weight of more than 14.5 stone in a person 5ft 9in tall. Now the latest results are in - and it looks like vindication for the late Dr Robert Atkins, whose diet books have sold 15 million copies over 30 years.

According to Dr Brehm, those following Atkins's low-carbohydrate diet for four months achieved twice the weight loss of those on a conventional calorie-controlled, low-fat diet. Furthermore, the team found no evidence of harmful effects from following the diet - at least over the timescale of the study.

These results are in line with those found in similar small studies now starting to emerge. As well as backing the claims made for the Atkins diet, these latest results seem to further undermine standard nutritional advice about the need to focus on cutting fat and calories. They are certainly something of an embarrassment to Dr Brehm, whose research is funded by the American Heart Association, which has long advocated calorie-controlled, low-fat diets.

As a scientist, Dr Brehm puts unearthing the truth above pleasing her paymasters - but it is this that is causing her most concern. She is having problems explaining her findings - and in the increasingly vociferous debate over the Atkins diet, that may well land her in a lot of trouble at next week's meeting.

The scientific world is becoming increasingly polarised in its views over the diet, with researchers such as Dr Brehm being given a tough time over their apparent support for what some scientists believe is the nutritional equivalent of crystal therapy. At the heart of the controversy is the science behind the Atkins diet - first published 30 years ago - and whether it is really anything more than a collection of buzzwords.

Conventional wisdom dictates that calories are the key to weight loss, and so those who lose weight must simply be consuming fewer calories than they burn up. Yet according to Dr Brehm, the obese people who lost weight on the Atkins diet ate and burned up essentially the same number of calories as those on the standard diet. What was very different was the proportion of body fat shed by each group, which mirrored their percentage weight loss. On the face of it, this backs the central claim of the Atkins diet: that a low-carb diet turns the body into a "fat-burning machine".

To trigger this effect, Atkins dieters are instructed to begin by eliminating all but 20 grams of carbohydrates from their diet for a fortnight, forcing their bodies to get energy by burning up fat reserves instead. The result is supposed to be weight loss, plus the production of compounds known as ketones; the higher the level of "ketosis", the more fat is being burned.

That is the theory. Yet studies of the patients in Dr Brehm's trial failed to reveal a connection between ketosis and fat loss. "We didn't see any correlation - all of our expectations were confounded," she told The Sunday Telegraph. "I'm hoping someone in the audience might have some answers."

Dr Brehm is confident that there is a reasonable - if not simple - explanation for her findings: "In the end, the energy in has got to match the energy out," she says.

Still more baffling is why there are such huge gaps in knowledge about how humans respond to diet. The past 20 years has seen obesity reach record levels in the UK, with more than 20 per cent of adults now classified as clinically obese. According to the National Audit Office, obesity is responsible for 30,000 premature deaths each year - more than 50 times the number of Aids-related deaths in the UK.

Such statistics have led scientists to concede that the standard advice on nutrition and healthy eating has been an abject failure. Even so, official sources such as the British Nutrition Foundation continue to promote the standard high-carbohydrate, low-fat diet. Meanwhile, the Atkins diet is officially dismissed as a "fad" by the British Dietetic Association, with leading nutritionists insisting that there is insufficient scientific evidence to go on.

This lack of evidence has not deterred many in the medical profession from condemning the diet out of hand. Last week a poll of GPs revealed that one in four would advise their patients to stay fat rather than try the Atkins diet - despite the proven life-threatening effects of obesity.

According to some, such attitudes suggest that the scientific world is in the grip of cognitive dissonance over the Atkins diet, preferring to ignore whatever evidence it does not like. Professor Eric Westman, a clinical trials expert at Duke University, North Carolina, and author of a forthcoming study of the evidence for and against the Atkins diet, says: "It is making people re-examine dogma - and it's not always appreciated."

According to the review, to appear in Current Atherosclerosis Reports, studies to date show that the Atkins diet does produce weight loss over six months, without obvious health effects. And contrary to the claims of many nutritionists, there is even evidence that it may be healthier than the standard diet. Despite its promotion of fat and eggs, studies suggest that the diet may boost levels of the healthy forms of cholesterol.

Prof Westman thinks that this unexpected effect may explain a long-standing mystery surrounding heart disease. In the late 1980s, researchers began investigating the unusually low rates of heart attacks and stroke among Eskimo communities in Greenland. Until now, the explanation was thought to lie in their diet of oily fish. Yet attempts to reduce heart disease using supplements of fish oil extracts proved disappointing. Prof Westman says the studies of the Atkins diet point to another explanation: that the lo-carb diet forced on the Inuit by their environment gives them higher levels of healthy forms of cholesterol, proven to cut heart disease risk.

Despite this, Prof Westman cautions anyone with a medical condition against rushing onto a low-carb diet. "The problem is that it works too well," he explains. "The diet can cause insulin levels to drop by 50 per cent in one day, so diabetics could find themselves over-medicated. It's the same for those with high blood pressure."

Even so, Prof Westman believes that the results to date are impressive enough to warrant an intensive research effort on the Atkins diet: "We're in a period when we will learn a lot."

It is not a prospect that thrills the whole nutrition science community. Prof Westman has been personally vilified for conducting research with financial support from the Atkins Foundation - despite the fact that some vocal critics of the diet, such as Dr Susan Jebb, the head of nutrition at the UK Medical Research Council, have received funding from bodies such as the Flour Advisory Bureau.

Dr Brehm has also run into resistance even over her research findings that were funded by the American Heart Association. "We had a tough time getting our results published - it took 18 months altogether," she said. "The big journals really couldn't handle it. But we're not endorsing the diet, it's just our results."

What both sides do agree on is the paucity of scientific evidence on the long-term benefits and health effects of the Atkins diet. With the world-wide obesity problem now claiming an estimated two million adult lives a year, Dr Brehm believes that the time has come to commit serious resources to studies of low-carb diets. She said: "We need much more doing - and doing quickly."

It is a sentiment endorsed by Professor Tom Sanders, the director of the Nutrition, Food and Health Research Centre at King's College, London - and a sceptic of the Atkins diet. "The evidence is that it's the calorie intake that counts," said Prof Sanders. "But in the end, diets don't work because people don't follow them. We need large scale, randomised controlled trials of treatments of obesity running for one to two years."

Those already embarked on such research suspect that it will take a great deal to overcome the visceral response the mere mention of Atkins provokes among academics. Says Dr Brehm: "A lot of people just want to hold on to what they learned in college."

Source: telegraph.co.uk