A major, well-designed research study of the effectiveness of various “diets” on weight loss and health has been published in the current issue of the New England Journal of Medicine. The researchers carefully followed 322 moderately obese people (mostly middle-aged men) for two years in a workplace setting where a lot of support and education was given along with a controlled diet. The research subjects were divided into three groups who ate one of the following: a low-fat, restricted-calorie diet; a Mediterranean, restricted-calorie diet; or a low-carbohydrate, non–restricted-calorie diet. In the final analysis, all three groups lost weight (mostly in the first six months) and had health benefits, but the Mediterranean and low-carb groups had the best outcomes. Overall, 85% of subjects stuck to their diet for the full 2 years.
What we can learn is that education, structure and support are important in maintaining a consistent eating pattern (this study took place in Israel where the mid-day meal is traditionally the main meal, so the impact of the workplace is significant). We also learned that the two diets with the best outcomes (in terms of weight loss maintenance, reduction in waist circumference, and some health measures) were the Mediterranean and low-carb. Finally, as written in the original article, we learned:
Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets. The more favorable effects on lipids (with the low-carbohydrate diet) and on glycemic control (with the Mediterranean diet) suggest that personal preferences and metabolic considerations might inform individualized tailoring of dietary interventions. … The low-carbohydrate and Mediterranean diets had some beneficial metabolic effects, a result suggesting that these dietary strategies might be considered in clinical practice and that diets might be individualized according to personal preferences and metabolic needs [e.g., diabetics might do better on the Mediterranean diet; people with lipid problems might choose the low-carb diet]. The similar caloric deficit achieved in all diet groups suggests that a low-carbohydrate, non–restricted-calorie diet may be optimal for those who will not follow a restricted-calorie dietary regimen. The increasing improvement in levels of some biomarkers [health indicators] over time up to the 24-month point, despite the achievement of maximum weight loss by 6 months, suggests that a diet with a healthful composition has benefits beyond weight reduction.
One limitation of the study is the fact that most of the subjects were middle-aged men (only 16% were women).
Diet research is hard to do, and this study benefited from having a relatively controlled setting (workplace with main meal being served there). This is also a weakness, because few in the real world have that much structure and support.
The take home message for me is that even with almost ideal conditions it is hard to lose much weight, but weight can be maintained after the initial six months and the health benefits continue in the maintenance phase. Also, the study does help us (a little) choose what kinds of foods to add or subtract from our permanent diet (lifestyle), as opposed to a temporary “weight loss” diet. So, for example, I may decide to add more fish and chicken (and less red meat), more Tabouli (I love it), and less sugar and starch (if I cut way down on these, I won’t have to count Calories so much). Nothing we didn’t already kind of know, but this is reinforcement for that.
For a more detailed summary of the research see this site.