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Battle of the Bulge

Scientists study popular diets: Who wins the war on weight loss?

If you look at any list of best-selling books, you’re likely to find at least one on weight loss. That isn’t surprising, considering that one-third of Americans are clinically obese and that the figure is rising. While excess fat may be undesirable from an aesthetic viewpoint, carrying it around places a severe burden on the body that’s linked to many degenerative diseases, including cardiovascular disease and cancer. Fat isn’t the inert storage site that many thought it was. Instead, fat is extensively active, releasing chemicals that have far-ranging effects on health.

The question is, What’s the best way to lose excess bodyfat via dieting? Scientists say that you must increase activity and eat fewer calories than you burn in activity. That solution isn’t attractive to many people, as most seek an easier, less painful method of shedding excess pounds. If you can present a diet plan that appears to help people effectively lose fat yet somehow avoid food deprivation or hunger, you’ve got a best-seller in the making.

Some of the most popular diet plans include the Atkins low-carb diet; the Zone diet advocated by biochemist Barry Sears; the Weight Watchers diet, a plan usually favored by women; and the Ornish low-fat plan. Which one is best?

A recent study didn’t seek to determine the superiority of any particular diet but instead focused on the health and adherence aspects of the plans, as well as their cardiovascular benefits’or lack of same.1 One hundred sixty subjects, age range 22 to 72, were randomly assigned to one of the four popular diet plans. All subjects had at least one cardiovascular risk factor, such as high blood pressure or elevated blood cholesterol. They were monitored for a year.

Those in the Atkins group began with a carb intake of only 20 grams a day, gradually increased to 50 grams. They got relatively large amounts of fat and protein. Those in the Zone group followed the Zone precepts of carb, fat and protein percentages of 40, 30 and 30, respectively. The Weight Watchers group could eat any food but counted points, with each point averaging 50 calories. The Ornish diet, developed by cardiologist Dean Ornish, limits fat intake to no more than 10 percent of total calories. The participants were told to exercise about an hour a day and maintain a food diary.

The first finding that stood out was the lack of adherence to any of the diets. Only 58 percent of the subjects maintained their diets for one year. The greatest dropout rates occurred in the Atkins and Ornish groups, which were considered the most restrictive of the diet plans. But even those who stuck with their diets cheated more as time went on. Those who persevered lost between 4.6 and 7.3 pounds over a year. One aspect of this study that didn’t make sense was advice given to the participants that they could adjust the diets any way they wanted after two months. Those in the Atkins low-carb group increased their carb intake to 190 grams by the six-month mark, which means they were no longer on the Atkins or any other low-carb plan. Even those in the Ornish lowfat group were eating an average of 30 percent fat by the end of the study, or three times the maximum suggested.

The diets varied in their effects on cardiovascular risk factors. All the diets except the low-fat Ornish plan led to a higher level of protective high-density-lipoprotein cholesterol. The lower-carb diets, such as the Atkins and Zone plans, showed greater reductions in blood triglyceride (fat), diastolic blood pressure and insulin. The authors say their results don’t support the notion that low-carb diets are superior to standard diets in terms of weight loss or cardiovascular benefits’a notion disputed by other recent studies. Besides, as noted above, those in the low-carb group had abandoned their low-carb diets by the study’s halfway point.

The authors also suggest that the best diet is the one that you stick with. Adherence is a major problem with most diets, especially among those who aren’t highly motivated. That’s rarely a factor with bodybuilders, who are highly motivated to improve their appearance and lose fat, though many don’t consider the health aspects of dieting.

The study didn’t examine the effects of what are probably the best diets overall with respect to promoting health and fitness, the Mediterranean diet and the so-called Paleolithic, or Stone Age, diet. Both are moderate in carbs but feature a lot of the nutrients and food factors known to prevent most degenerative diseases. They’re the best long-term diets to follow, without a doubt. IM

1 Dansinger, M.L., et al. (2005). Comparison of the Atkins, Ornish, Weight Watchers and Zone diets for weight loss and heart disease risk reduction. JAMA. 293:43-53.

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