Imagine that you are between the ages of 40 and 65, are overweight, and have decided that it is time to lose weight. Being more compulsive than most of us, you undertake to compare three widely-touted approaches to weight reduction: the American Heart Association-recommended low- fat, low-calorie diet; the moderate fat-restriction and moderate calorie-restriction Mediterranean diet; or the low-carbohydrate no calorie-restricted (Atkins) based diet.
Just such a study, comparing the three diets in randomly-assigned volunteers, was carried out at the International Center for Health and Nutrition, Department of Epidemiology and Health Systems Evaluation, Ben-Gurion University of the Negev, and reported in The New England Journal of Medicine in 2008. The program included ongoing contact with and encouragement by trained dietitians who kept in touch with all participants over the course of a two-year study. All participants were weighed regularly at their workplace and blood tests were taken at pre-defined intervals.
Interestingly enough, within the framework of the study and with the ongoing supervision of a dietitian (and accepting that these were well-motivated volunteers) at the end of one year, 95% were still following their diets. At the end of the second year, compliance was lower at 85%; 90.4% in the low-fat group; 85.3% in the Mediterranean diet; and 78.0% in the low-carbohydrate group. All participants lost weight and the patterns of weight loss were similar, with the maximum weight loss taking place in the first six months of the program and the last eighteen months being primarily maintenance of the weight reduction.
There were differences in the amount of weight loss. Average weight loss in the low-fat (AHA) group was 2.9kg, 4.4kg for the Mediterranean diet and 4.7kg in the low-carbohydrate (Atkins) diet. Waist circumference and blood pressure reductions were equivalent in all three groups. What was also striking was that HDL cholesterol (the “good” cholesterol) increased in all three groups with the largest increase being in the low-carbohydrate – high-fat diet. LDL cholesterol did not change significantly.
The take-home message appears to be that a supervised program with well-intentioned volunteers and regular exercise, combined with either the Mediterranean or the Atkins diet, is as effective as the traditional low-fat, low-calorie diet – and possibly even more effective..
Does this establish scientific truth? No! As I have written in this magazine previously, truth becomes approximated when several well-done studies yield similar results. This was a well- done study and credit goes to the team at Ben-Gurion University of the Negev who carried it out. We eagerly await confirmatory studies, but in the interim we each have some justification for choosing the diet to which we feel we can adhere in order to prolong our healthy and enjoyable lives.