Low Carb and Low Fat Diets Work Best with Support

Experts on diet and weight loss report a study that compares weight loss after two years on a low-carbohydrate diet versus a low-fat diet when both were combined with a program to help people change their lifestyle.

The study says that when combined with extensive guidance about eating and exercise, people lost about the same amount of weight whether they were on low-carb diet or a low-fat diet.

The study is reported in the Annals of Internal Medicine.

"In general, dieters should be less concerned about what diet they're on and more focused on finding strategies to stick to the diet they chose," advises study author Gary D. Foster, Ph.D., at Temple University in Philadelphia.

Low-Carb Diet Has Extra Benefits

However, the researchers also found that people in both groups only lost an average of about 7 percent of their weight two years after beginning their diet. Many participants were very overweight at the start of the study.

And those who were on the low-carb diet did get one extra benefit: Their blood pressure and levels of "good" cholesterol improved a bit more than those who cut down on fat.

There has long been research into which diet is the best. But this study is unique because it looks at how diets work over the longer term, says Dr. Foster.

In the study, funded by the National Institutes of Health (NIH), researchers followed 307 overweight people for two years as they participated in a low-carb diet - fashioned after the Atkins diet - or a low-fat diet that was also low in calories.

Their average age was 45 and their average body mass index was 36, meaning they were typically obese, a step beyond simply being overweight.

Those on the low-fat diet were told to eat 1,200-1,800 calories a day, with fewer than 30 percent of them from fat. Those on the low-carb diet were instructed to eat no more than 20 grams of carbs a day, although they could eat all the fat and protein they wanted.

In addition to dieting, the participants received guidance about dieting and exercise similar to that offered in commercial weight-loss programs, notes Dr. Foster.

On average, the participants lost 7 percent of their weight after two years, or an average of about just over 15 pounds. The results were similar, no matter which diet they were on.

Importantly, levels of "good" cholesterol grew by about 11 percent in the low-fat group but more than twice that - about 23 percent - in the low-carb group. Blood pressure also fell by a greater level in the low-carb group vs. the low-fat group.

Sticking to Calorie Reduction

It is not clear why the low-carb group might perform better in those areas, observes Dr. Foster, but the two differences are significant. Still, he says, "we can't say following this diet or that diet will result in less heart disease."

Overall, he said, the message of the study is that the diets work about equally well when it comes to weight loss.

Howard Sesso, Ph.D., at Brigham and Women's Hospital in Boston, says this suggests the kind of diet that a person adopts may be less important than his or her ability to stick to it.

There is another message from the study, explains Lona Sandon, R.D., at University of Texas Southwestern Medical Center. "It confirms what we have known for years: that it's not fat versus carbohydrates. It's the calories that lead to weight loss."

Losing weight and keeping it off takes serious commitment, says Sandon. For most, their lifestyles and environments just don't support that kind of commitment.

Always consult your physician or other healthcare provider for more information.