After decades of ridicule by the American medical establishment, it’s fittingly ironic that Dr. Robert Atkins had his epitaph published in the New England Journal of Medicine. Atkins, who died on April 17 at age 72, spent most of his life advocating a diet low in carbohydrates and high in fat and protein. The May 22 issue of the journal contained two studies that examined the effects of such low-carbohydrate diets. Both studies were led by Penn faculty and both offered a qualified vindication of the Atkins approach, concluding that it is an effective weight-loss regimen and—to the authors’ surprise—a safe way to reduce cardiac-risk factors.
One study was led by Dr. Gary Foster, an associate professor and the clinical director of Penn’s Weight and Eating Disorders Program, a multi-center operation that put the Atkins plan head-to-head with the Department of Agriculture’s Food Pyramid guidelines. Having received independent funding from the National Institutes of Health (NIH), the year-long study isn’t vulnerable to the criticisms leveled at some previous research, particularly studies that were paid for and initiated by the Atkins Center.
At the three- and six-month marks, Foster’s team found that the participants lost significantly more weight on the Atkins diet (at six months, 15.4 pounds on Atkins versus 4.2 pounds on the low-fat diet). Even more important, the Atkins dieters registered greater increases in “good” cholesterol (HDL) and greater decreases in triglycerides (fats in the blood) than those following the conventional diet.
Foster’s findings were echoed by another study, led by Dr. Frederick Samaha, assistant professor of medicine at Penn and head of the cardiovascular division at the Philadelphia Veterans Affairs Medical Center. It examined a group of 132 severely obese men and women (average weight: 286 pounds) with a high prevalence of diabetes. After six months, the participants lost an average of 12.8 pounds on Atkins versus 4.2 on the low-fat, calorie-restricted diet, and showed a “relative improvement in insulin sensitivity and triglyceride levels.” (The authors also said the findings should be interpreted with “caution,” given the “small magnitude” of weight-loss differences and the relatively short duration of the study.)
The only apparent drawback to the Atkins diet, as reported in the Foster-led study, is that after a year, the participants had regained about a third of their lost weight. While that still amounts to an average net loss of 9.7 pounds, or four pounds more than the low-fat dieters reported, it also suggests that the Atkins diet is difficult to adhere to for more than one year.
For Foster, the decision to study the Atkins diet was difficult, primarily because of the stigma it carries in the medical community. “There are some negative connotations,” Foster says. “He [Atkins] has flown in the face of conventional wisdom for a long time, and hasn’t done it in a particularly scientific way … It’s sort of like abortion, it seems to me. People feel very strongly about it, on one end or the other. There’s lots more opinions than data.”
This lack of empirical data, combined with the diet’s overwhelming popularity, was what ultimately convinced Foster of the need for a long-term study. “I consider it a public-health issue. If 10 million copies of this book have been sold and people are doing the diet, we ought to know something about it in the scientific community,” he says, referring to the perennial bestseller Dr. Atkins New Diet Revolution, which has actually sold 15 million copies since 1972. “From my vantage point, we’re not doing well in the long-term treatment of obesity, so we need to take alternatives seriously. Not every quack thing that comes down the pike, but for obvious reasons Atkins is a longstanding, popular diet.”
Unlike many previously published reports on low-carb dieting, Foster’s study was the first to follow the strict Atkins regimen verbatim. At the outset, participants met with a dietician and were given either the Atkins-authored book or a manual on the Food Pyramid—the standard low-calorie, high-carb diet (the guidelines for which may soon be revised by the federal government). After this initial meeting, however, the dieters were left to their own devices. This self-help model was intended to mimic the way most people attempt to lose weight, but, of course, it also mimicked the high attrition rate that’s so common with dieting in general.
By the end of the 12-month study, 39 percent of the Atkins dieters had dropped out. On the flip-side, the conventional diet had a 43 percent dropout rate. So, while neither diet was easy to stick to, the lack of bread, rice, and sweets in the Atkins approach didn’t make it any more difficult to follow.
One interesting—and under-reported—finding in Foster’s study is that subjects following the Atkins diet lost weight regardless of whether or not their body was in a state of ketosis (having excess ketones, a byproduct of fat metabolism).
That debunks a long-held belief by the Atkins camp that its diet functions on an alternate metabolic system, whereby the human body burns fat stores, generating ketones when it is deprived of carbohydrates. Although Foster found that some subjects did indeed produce ketones, it wasn’t an appreciable amount and it wasn’t predictive of weight-loss.
So, if ketosis is a scientific red herring, what then explains the Atkins diet’s effectiveness? “From a scientific point of view, there’s no way to explain great weight loss besides eating fewer calories or exercising more,” says Foster. In other words, despite unrestricted amounts of butter, mayonnaise, and T-bone steaks, the subjects following Atkins consumed fewer calories than the low-fat dieters. To skeptics who suggest that the diet is thus of little consequence, he responds: “We’ve got an epidemic of obesity and we’ve got to find ways that are more palatable for people to lose weight. If low-carb diets help you do that—if they make you less hungry, if they make you more full, and it’s more tasty—then we have to look at that.”
To that end, Foster and his colleagues have secured additional grant money from the NIH to continue studying the long-term effects of low-carbohydrate dieting. They are currently enrolling participants for a five-year study, in which they plan to measure such things as kidney function, endothelial function (the elasticity of arteries), and people’s ability to exercise.
Ultimately, Foster hopes that his follow-up research will explain why the Atkins diet works for some sub-groups, but not for others. “It may be that people who have high insulin-resistance do better on a low-carb diet, but people who have okay insulin-resistance do better on a high-carb diet,” he says. “Those kinds of sub-types are exactly the questions we need to be asking in the field. Not why it works or doesn’t work, but for whom and under what conditions.”
—Ted Mann C’00