Low-fat, low-carb-which is best?

The news is out. Low-carb is as good as low-fat for losing weight, and may be even better for your cholesterol. The Mediterranean diet is better for reducing fasting glucose according to the study that was published in the New England Journal of Medicine this week. In the same issue of the NEJM there is a book review on the latest thinking on Metabolic Syndrome, the collection of biomarkers that puts a person at high risk of diabetes and heart disease at the very least. Apparently about 60% of those over 60 years of age in the US suffer from Metabolic Syndrome (previously known as Syndrome X, and maybe now known as Dys-metabolic Syndrome) which manifests as abdominal obesity, high blood pressure, insulin resistance and an unfavorable cholesterol profile. The NEJM study showed the Mediterranean diet reduced fasting glucose, while the low-card diet yielded better weight loss and an improved cholesterol profile which made me think that either of these diet approaches could have far-reaching health benefits beyond weight loss if we took a closer look at what such diets do to Metabolic Syndrome as a whole.

The study took two years and participants appeared to remain compliant to the diets they were assigned. Weight loss was between 3 and 6kg for all groups with the least in the low-fat group and the most in the low-carb. The low-carb group, was the only group where calories were not restricted. Perhaps the low-carb diet curbs appetite in itself?

The article was interesting because it cobbled a sacred cow that says low fat diets reduce cholesterol. From this study it seems you are better off with low-carb to improve your cholesterol profile. The low-carb increased HDl and decreased LDL, whereas the low-fat diet had a negligible effect on LD although it did raise HDL.

The study has some flaws; it relies on self reporting for dietary compliance although relatives were instructed to encourage participants to stick to the plan. There were also few women in the study which is significant because the data did suggest some gender-based differences in effects of the three diets. Overall, I found the data interesting, and hope to see more of these longer term studies that study the effect of dietary composition on factors relating to weight and health. If 60% of us are truly suffering from Metabolic Syndrome, and hence will be looking for ways to slim down and de-fat our blood streams in the future, then the more of this type of study the better. Or maybe not. As Michael Pollan (author of In Defense of Food, 2008, The Penguin Press) might say, there should be little need to tell us what our bodies already know. We evolved to eat. Not too much, Mostly plants.

So why does it seem so hard?

Shai, I., et al., ., , . (2008). Weight loss with a low-carbohydrate, Mediterranean, or low-fat diet.. New England Journal of Medicine, 359(3), 229-241.