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What Do the New Studies on Low-Carb Diets Really Mean?

Straightening out the mixed messages from the media

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Updated May 28, 2004

Updated May 28, 2004
By DrRich

Researchers published 2 new studies on low-carbohydrate diets last week in the Annals of Internal Medicine, and while the general media reported widely on these studies, the messages they conveyed were mixed. Some reports indicated that low-carb diets were better than more conventional low-fat diets; other reports indicated the opposite, that low-carb diets turned out to be no better than low-fat diets. Few reports mentioned anything at all about the blood lipids of patients on low-carb diets.

What did the studies actually show?

One study, from the Philadelphia VA Medical Center, reported the 1-year findings in 132 obese adults randomized to either low-fat or low-carb diets. The second study, from the Duke University Medical Center, reported the 6-month results in 120 overweight, hyperlipidemic patients randomized in the same way.

Both studies showed a greater long-term weight loss in patients treated with low-carb diets as compared to low-fat diets, but the difference in weight loss was statistically significant in only one of the studies (the Duke study).

However, both studies showed that over the long-term, changes in blood lipids were more favorable in the low-carb patients than in the low-fat patients. In particular, the low-fat diets resulted in reduced HDL cholesterol in both studies, while the low-carb diets resulted in significantly better HDL levels than in the control groups. The same was true for triglyceride levels.

What this means

First, it appears that the major objection to low-carb diets - that reducing carbohydrates in favor of fats and protein in the diet would worsen blood lipid levels - is not actually a problem. Indeed, low-carb diets appear to result in favorable metabolic changes.

Second, patients on low-carb diets tended to lose more weight over the long term than patients on low-fat diets, but the difference in weight loss was not particularly impressive.

The bottom line

Honest medical observers are now forced to consider low-carbohydrate diets as possibly reasonable alternatives for many of their patients; the diets can no longer be dismissed out of hand as obviously dangerous and harmful. If anything, contrary to popular expectations, low-carb diets improve the lipid profile.

However, proponents of low-carb diets should now temper their more outlandish claims about how much weight a person will lose on a low-carb diet. While weight loss occurs, it is often not dramatically better than with other kinds of diets.

Why is the early weight loss seen with low-carb diets often not maintained? Whatever type of diet is chosen, weight loss depends on consuming fewer calories than one expends. For one reason or another, even with low-carb diets enough calories are often consumed to prevent dramatic weight loss. Perhaps this is a function of all the "low-carb" snacks now being marketed, which, while probably low in carbohydrate content, are nonetheless absolutely loaded with calories. DrRich has observed many citizens consuming these snacks in prodigious quantities. Just as you can get fat eating the previously popular "low-fat" snack foods (which were jam-packed with carbs,) you can also get fat eating currently popular "low-carb" snack foods.

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