Recent evidence on low-carbohydrate diets

I first heard of the Atkins diet back in medical school 12 years ago when one of my classmates abruptly began eating steak without potatoes and hamburgers without the bun. I was skeptical that this odd regimen would work, but his experience and subsequent research has shown that low-carbohydrate diets are as effective as traditional low-calorie, low-fat diets for losing weight.

A more important question is whether a low-carbohydrate diet, which includes higher amounts of protein and fat than the typical higher-carb diet, is as good for your heart in the long run. Two recent studies published in the journal Annals of Internal Medicine seem to provide conflicting answers. In the first study, researchers randomly assigned 307 overweight adults to a low-carbohydrate or a low-fat diet, in addition to exercise counseling. After 2 years, participants in both groups had lost an average of about 15 pounds, but the low-carbohydrate group had a significantly greater increase in HDL "good" cholesterol.

The second study, though, found that all low-carbohydrate diets aren't created equal. This one followed 100,000 male and female health professionals over a period of 20 years or more to see whether the amount of carbohydrates, fat and protein they ingested had any impact on their health. Participants whose diets were classified as the lowest in carbohydrates were 12 percent more likely to die during the study than those who consumed the highest amount of carbohydrates. But it was the low-carb, meat-loving folks who had the highest risk of death from heart disease and cancer compared to low-carb dieters whose protein sources were mostly vegetables.

So which study should you believe? Unfortunately, neither provides a definitive answer about whether low-carb diets are good or bad in the long run. Although the first study confirms that low-carb diets lead to weight loss and an increase in HDL cholesterol, that doesn't mean followers of these diets will wind up with less heart disease down the road. Also, participants in the first study had access to trained health counselors who met with them 37 times over two years to make sure that they rigorously adhered to the diet and exercise plan—a valuable resource that most people can't afford. While the second study provides more long-term data on low-carb diets, the researchers couldn't control for every factor that might affect a person's risk of dying such as, for example, exposure to air pollution. Rural folks might be more likely to eat more plant proteins like soybeans, while also having less exposure to air pollution than urban folks who might gravitate towards meat-based meals. So the type of protein people ate may not have been completely responsible for the difference in death risk.

If you're thinking of trying a high-protein, low-carb diet to lose weight or improve your health, consider the following factors based on the latest research.

1) You have a good chance of losing weight if you follow the diet faithfully, and you will most likely find it easier to stick with than a low-fat diet.

2) In order to keep off any weight you lose, you need to increase your physical activity. Aerobic exercise (walking, jogging, swimming) produces better results for weight maintenance than strength-building exercises (pushups, lifting weights), though a combination of both types may offer additional health benefits, such as prevention of injuries.

3) Although low-carb diets have been shown to improve cholesterol in some people, we don't know if they protect against heart problems in the long run. One thing I do know: If a diet sounds too good to be true, it probably is. In this case, current research is consistent with common sense. Replacing carbs with tofu and steamed vegetables is likely to be better for your health than baby-back ribs and pork loins.

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The above post was first published on my Healthcare Headaches blog at USNews.com.