According to leading nutrition experts, the best diet for weight loss and overall health is a diet low in total fat.  Low-fat diets have long been considered the gold standard for both weight loss and general health.  However, when less fat-restrictive diets such as low-carbohydrate diets and Mediterranean-style diets, rose in popularity, experts were forced to consider the possibility that these alternative diets also successfully promoted weight loss.  Still, skeptics wondered about the physiological safety of such alternatives.  They argued that Atkins-type diets could negatively affect cholesterol levels and glucose metabolism. 

Now, it turns out that such fears are unfounded.  A two-year Israeli study, recently published in The New England Journal of Medicine, concludes that low-carbohydrate and Mediterranean-style diets are as effective for weight loss as low-fat diets.  Moreover, not only do low-carbohydrate diets have enhanced positive effects on participants' lipid profiles, but Mediterranean-style diets outscored both the low-fat and the low-carbohydrate diets in glycemic control.  While follow-up studies confirming these findings are important, nurses should not feel bound to endorse only low-fat dietary plans when educating patients about nutritional choices.

The authors of the study, Shai et al, enrolled 322 overweight or obese subjects and randomly assigned them to one of the following three diets; low-fat, low-carbohydrate, or Mediterranean-style.  The low-fat diet was based on American Heart Association guidelines.  It was calorie-restricted, cholesterol-limited, and only ten percent of total caloric intake was comprised of saturated fat.  The low-carbohydrate diet was not restricted by calories, fat, or protein, although carbohydrate intake could not exceed 120 grams daily.  The Mediterranean diet was limited by calories, and fat intake was capped at 35 percent of total caloric consumption.  At regular intervals, all participants' weights, fasting blood glucoses, and cholesterol levels were checked.

By the twenty-four month mark, 272 participants remained in the study.  All of them lost weight.  Those assigned to the low-fat group lost a mean of 6.6 pounds; the Mediterranean-diet participants lost a mean of 9.7 pounds; and the low-carbohydrate group lost a mean of 10.3 pounds.  Authors speculate that weight loss in the Mediterranean and low-carbohydrate groups may have been higher than the low-fat group because the former diets were more forgiving.  The low-carbohydrate participants, for example, were not limited at all in the amount of food they consumed as long as chosen foods met the stated criteria. 

Additional benefits upon serum biomarkers were surprising.  The low-carbohydrate diets significantly decreasing LDL and increased HDL cholesterol levels, an unexpected result given that this group consumed the most fat.  Further, Mediterranean-style diets produced pronounced improvements in glucose metabolism and insulin stabilization. 

This information has important ramifications for overweight people with heart disease and type 2 diabetes.  Medical professionals should take note of these results. Patients can and should be given greater latitude in selecting individualized dietary plans. 

Reference:

Shai I, et al. (2008, July). Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet. The New England Journal of Medicine, 359, 229-241.

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