Pro & Con; Low-carb diets: are they safe and effective?(Opinion)

YES

With the low-carbohydrate diet craze sweeping the nation, concerned doctors have worried about emergency rooms filled with patients whose arteries are clogged. As many as 40 million people have tried low-carb diets in the past decade, yet these problems have not materialized.

Low-carb advocates make four central claims about this approach: Dieters will lose more weight and keep it off; calories count less than where the calories come from; dieters take in fewer calories because they aren't as hungry; and the changes are safe enough to last a lifetime.

Does the evidence bear out these claims? The long-term jury is still out, but the answer so far is more yes than no.

I reviewed one metaanalysis and three randomized controlled trials, all published in 2003, that looked at obese subjects on low-carb diets (typically less than 60 g/day, but in one study less than 30 g/day) versus patients on low-fat diets.

Low-carb dieters did lose weight. In all three trials, subjects on the low-carb diets had lost a lot more weight than their low-fat, low-calorie counterparts after 6 months (N. Engl. J. Med. 348[21]:2074-81, 2003; N. Engl. J. Med. 348[21]:2082-90, 2003; J. Clin. Endocrinol. Metab. 88[4]:1617-23, 2003). One study followed dieters for an additional 6 months and found that after 12 months, low-carb dieters had lost no more weight than those on the conventional diet. In the meta-analysis greater weight loss was associated with fewer calories and longer duration, but not with carbohydrate content (JAMA 289[14]:1837-50, 2003).

These studies don't directly address the third claim, that low-carb dieters have less hunger than other dieters. But in the two randomized trials that reported calorie intake, those on a low-carb diet ate the same number of calories as those on a low-fat, low-calorie diet, even though the low-carb folks had no calorie restrictions.