A study appeared in the current issue of the Journal of the American Medical Association (JAMA) slated to land on doctors’ desks tomorrow that will, I’m sure, make all the major news services. This study purports to show that a long term low-fat diet doesn’t cause weight gain, and that it actually brings about a weight loss.
You will be able to witness the bias in the reports on this study by how enthusiastically the writers embrace the supposed findings.
It’s all pretty much nonsense, however, as the study didn’t really show anything much at all.
The researchers randomized almost 50,000 women between the ages of 50 to 79 into a study group, the members of which consumed a lower-fat, higher-carbohydrate diet, and a control group, the members of which continued on with their regular diets. These two groups were followed for almost nine years, and were evaluated for dietary compliance and weight loss along the way.
During the first year the members of the study group (the low-fat group received constant attention from the research staff whereas the control group were basically given a pat on the back and sent on their way.
Women assigned to the control group received a copy of the Dietary Guidelines for Americans as well as other diet- and health-related educational materials, but otherwise had no contact with study dietitians.
In contrast, women randomized to dietary intervention were assigned to groups of 8 to 15 participants for a series of sessions structured to promote dietary and behavioral changes that would result in reducing total dietary fat to 20% and increasing intake of vegetables and fruit to 5 or more servings and grains (whole grains encouraged) to 6 or more servings daily. Participants were informed that the diet was not intended to promote weight loss and were encouraged to maintain usual energy intake by replacing fat calories with calories from other sources, mainly carbohydrate. Eighteen group sessions were scheduled during the first 12 months, after which the session frequency was reduced to 4 per year for the duration of the trial. Individual contacts were completed in person or by telephone or mail for women who could not attend the sessions. Group activities were supplemented throughout the course of the study by an intervention protocol consisting of 3 individual interviews that used reflective listening techniques that were validated in a pilot study at 3 centers, targeted message campaigns, and personalized feedback.
So, we’ve got two groups of women, one of which has intense attention and counseling on dietary and behavioral changes while the other didn’t really get squat in terms of attention or care. What happened?
Hold on to your seat for this one.
During the first year the women in the group that got the constant attention lost a little over 4 pounds more than the women in the group that were ignored. By the end of the study the weight loss difference had narrowed to less than a pound.
All I can say is that if I conducted a study that showed these puny differences given all the time, effort, and instruction I had put into the control group, I certainly wouldn’t be crowing about it.
When the study results are probed a little, some interesting findings bubble to the surface, the most important of which is that the difference in caloric intake between the women in the two groups is about 120 kcal per day. If we multiply this 120 kcal per day times 365 days per year times 9 years, we find that over the course of the study the women in the control group consumed almost 400,000 (394,200 to be exact) fewer calories than did the women who ate what they wanted. If we take those calories and divide them by 3500 (roughly the number of calories in one pound of body fat) we find that, based on the reduction in calories alone, the women on the lower-fat, higher-carb study diet should have each lost over 112 pounds more than the women on the control diet. Yet they lost less than one pound more. Doesn’t sound much like a recommendation for the diet to me.
It’s interesting to see how the editors of JAMA have played this situation. Most medical journals make their full-text content available only to subscribers or to those who have university affiliations. Anyone can get the abstract, but the full test can be had only by a few. Occasionally a few of these journals – JAMA is one of these few – will release the full text of certain papers to the public that the editors feel are of considerable public health importance. This paper is one of those papers and can be had in full by clicking here.
What’s interesting is that this same issue of JAMA contains an editorial about this paper that is less than flattering. But, strangely, this editorial paper is not available to the public. What’s more, the editorial can’t even be had in abstract form.
What does this editorial say? Let’s hit the high spots.
It starts out thus:
The article by Howard and colleagues in this issue of JAMA, which reports on the largest, most ambitious randomized dietary intervention trial conducted to date, has concluded that a low-fat diet program does not produce weight gain. Despite the impressive features of this landmark study, the findings on long-term weight change are somewhat underwhelming.
It goes on to note:
The article by Howard et al is quick to focus attention on popular diets such as Atkins, the Zone, and Sugar Busters!, whose authors have blamed the current obesity epidemic in large part on the low-fat (high-carbohydrate) eating pattern advocated by most authorities during much of the past quarter century. Does the recent study refute allegations that the low-fat dietary approach caused weight gain on a national scale? Perhaps it does to some extent. On the other hand, despite some successes, overall the low-fat dietary approach has been a failure with the US public, [my italics] which is in desperate need of effective obesity treatment and prevention strategies.
The authors of the editorial point out, as I did in my post yesterday, that what is required for serious weight-loss is commitment and adherence to a program.
This is a general truth for virtually all aspects of medical treatment, especially for the most potent disease cures. Great results usually are predicated on great adherence levels. Modern medicine has much more work to do in the area of facilitating high long-term adherence levels. Focusing collective efforts on addressing this challenging aspect of obesity treatment and prevention would no doubt serve society well.
Unfortunately, the public has become so entrenched in current obesity prevalence and treatment trends that many have come to view lifestyle modification as a mediocre means of preventing and reversing obesity, but this could not be further from the truth. Many have accepted the belief that living in today’s society is incompatible with what is required to apply lifestyle changes, or even worseâ€”that they barely work. Inadequate lifestyle counseling by physicians might contribute to this perception. However, most able-bodied persons who can find a way to overcome the monumental logistical and psychological barriers that prevent the full application of lifestyle change can reverse obesity within months. It seems simplistic, but a potential solution for the obesity crisis depends directly on finding a means of properly dosing lifestyle change recommendations. The medical profession and society in general have underdosed this potent cure by a long shot.
And the authors end by finding the above study a little less than stupendous and recommending more work on self discipline.
Even though the WHI Dietary Modification Trial was not a weight-loss study, the modest weight-loss findings somehow still seem dissatisfying. Much more work needs to be done on the obesity front, including a concerted collective effort focused on developing reliable methods of facilitating high long-term adherence levels to substantial lifestyle efforts…
I wonder why the editors of JAMA saw fit NOT to make this editorial available for your reading pleasure when they were so fre with the actual article?
Remember all this as you read the press reports tomorrow rabbiting on about how the low-fat diet really does work.