Harvard Heart Letter

What the latest diet trial really means

Any diet that helps you take in fewer calories will help you shed pounds.

The "Atkins is best" headlines you may have seen in March 2007 had champions of the low-carbohydrate, high-fat diet smiling — and hoping that people wouldn't read the study on which the news reports were based.

An article in the March 7, 2007, Journal of the American Medical Association compared weight loss over the course of a year in 311 overweight but healthy women who used one of four popular diet plans: Atkins, the Zone (balanced protein, carbohydrate, and fat), Ornish (very low fat, very high carbohydrate), and the LEARN program (standard low fat, moderately high carbohydrate).

The women in all four groups steadily lost weight for the first six months. The most substantial weight loss occurred among women assigned to the Atkins plan, who lost an average of 14 pounds, compared with 6–8 pounds for the other three plans. After six months, most of the participants started to regain weight. At the end of a year, the women in the Atkins group were about 10 pounds lighter than when they had started, compared with 5.7 pounds for the LEARN group, 4.9 pounds for the Ornish group, and 3.5 pounds for the Zone group.

Read the fine print, though, and you realize that few of the women actually stuck with their assigned diets. Those in the Atkins group were aiming for 50 grams of carbohydrate a day but took in almost triple that amount. The Ornish dieters were supposed to limit their fat intake to under 10% of their daily calories, but got about 30% from fat. There were similar deviations for the Zone and LEARN groups.

Beyond carbs, protein, and fat

The real message of this and other head-to-head diet comparisons isn't that one type of nutrient is better than another. Instead, it is that you can lose weight with any diet that helps you eat less. "In the long run, finding strategies that guide you to match your food intake to the calories you burn matters far more than macronutrients like protein, fat, or carbohydrates," says Dr. George Blackburn, director of the Center for the Study of Nutrition Medicine at Harvard-affiliated Beth Israel Deaconess Medical Center. Diet books that focus on individual nutrients may be good for short-term weight loss but don't necessarily offer good advice for a lifetime.

One worry about the Atkins diet is that eating meat, cheese, and other fatty foods will be bad for cholesterol and heart disease. In this trial, though, cholesterol levels in the Atkins dieters were fine.

To make the Atkins approach work for your heart as well as your waist, make smart protein choices. A study published in 2006 in the New England Journal of Medicine showed that over a 20-year period, women who followed low-carb diets high in plant protein and good (meaning unsaturated) fats were less likely to have developed heart disease than those whose low-carb diets were high in animal protein and fat. "If you plan to follow a low-carb diet, skip the butter and sausage and go for olive oil and fish," says Dr. Walter C. Willett, professor of nutrition at the Harvard School of Public Health.