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I am sure that this study will not put an end to the controversies comparing various types of diets, but recent research published in the New England Journal of Medicine—coming from the Harvard School of Public Health—strongly suggests that, to achieve weight loss, it really doesn’t matter what type of diet you adopt…the important point is that you significantly reduce your caloric intake.

Most diet research involves short-term studies and a relatively small number of participants (or have many more participants of one sex like the Israeli study mentioned below), but this Harvard study went on for two years, and involved 811 participants, and each of those was randomly assigned to one of four diets:

* Low-fat, average protein: 20% of calories from fat, 15% of calories from protein, 65% of calories from carbohydrate
* Low-fat, high-protein: 20% fat, 25% protein, 55% carbohydrate
* High-fat, average protein: 40% fat, 15% protein, 45% carbohydrate
* High-fat, high-protein: 40% fat, 25% protein, 35% carbohydrate

All of the diets encouraged lots of fruits and vegetables, the participants were encouraged to do 90 minutes of moderate exercise weekly, and all underwent first individual, then later in the study, group weight-reduction counseling. All participants were encouraged to cut about 750 calories from their previous diet, but all people during the study ate at least 1200 calories per day.

The results: people in all four diet types lost an average of 13 pounds (5.9 kg.) after the first six months, and then after about a year, most people slowly gained back some of their original weight, but at two years, all four diet groups were about nine pounds (4 kg.) less than their original weights.

One important differentiating point was that those people who faithfully continued attending group-counseling sessions over the two years lost an average of 22 pounds (10 kg.) rather than nine pounds!

Now while this seems to be a good study, it isn’t perfect; for example, the study group was 62% female rather than the ideal 50%.  And an Israeli study published last year in the same journal showed that people who followed a low-carbohydrate diet for two years had a larger weight loss than those who followed a low-fat diet, but this study consisted mostly of men (86%), and the study was partially funded by the Atkins Foundation (which advocates a low-carbohydrate diet).

Without doubt, the diet wars will continue, and I will not be surprised if I report within the next two years a different large controlled study with completely different results. Still, I think we can take away a couple lessons: first, that cutting calories is the most critical factor in any diet. Daily calorie counting might well be worthwhile to make sure you keep to your daily goal. You could take this approach: choose whatever diet (Atkins, Ornish, Mediterranean, etc.) you can stick to! (Consult with your physician, and you might have to experiment with several to see which you can really follow.) Second, it’s likely that if you consistently work with group support or counseling while you diet, you will have better results.

Next post: a nutritious recipe idea from Brazil, whether you are dieting or not!