Carbs are OK: Certainly for Women

Abstract & Commentary

By Joseph E. Scherger, MD, MPH, Clinical Professor, University of California, San Diego. Dr. Scherger reports no financial relationship to this field of study.

Synopsis: In the largest randomized dietary intervention trial conducted to date, a low-fat predominately carbohydrate diet resulted weight maintenance over 7.5 years in postmenopausal women compared with a control diet higher in fat.

Source: Howard BV, et al. Low-fat dietary pattern and weight change over 7 years: the Women's Health Initiative Dietary Modification Trial. JAMA. 2006;295:39-49.

The women's health initiative (WHI) included a Dietary Modification Trial with the primary end points looking at breast and colorectal cancer. More than 48,000 postmenopausal women were randomized into either a dietary intervention with a goal of 20% calories from fat with a high intake of vegetables, fruit and grains, or a control group simply given nutrition information. At baseline, the women had a mean age of 62.3 years, mean body mass index of 29.1 (overweight), and a dietary fat intake of at least 32% of total calories.

This was not a weight loss trial, but the monitoring of the 2 groups included measuring body weight. The intervention group lost a mean of 2.2 kg during the first year and maintained this weight over 7.5 years. The control group had modest weight gain between ages 50 and 70. Among the women in the intervention group, the lower the fat intake the greater the weight loss. A greater intake of vegetables and fruit also resulted in greater weight loss. Grain intake was neutral with respect to weight.

The authors conclude that a low-fat predominately carbohydrate eating pattern does not result in weight gain in postmenopausal women.

Commentary

The low carb craze is finally winding down, and this study helps bring balance and sanity back into nutritional advice. Three recent studies did report that people assigned to a low-calorie, low-carbohydrate diet (with high protein and fat content) lost more weight during a 6-month period than did those assigned to a reduced fat diet.1-3 However, in the study which was extended to 1 year, no differences in weight loss were demonstrated.1 The long-term health effects of a high-protein and high-fat diet have not been determined, but raise considerable cause for concern with respect to cardiac risk factors.

What have we learned from the recent dietary swings with respect to carbohydrates, fat, and protein? Some might think confusion and cynicism, and there is no solution except eating less and exercising more. I think we have learned a lot about healthy eating and some clues for weight loss and weight maintenance. This study is large and gives us limited, but important, information. A healthy diet consists of vegetables, fruits and grains, is low in fat, and does not result in weight gain. Note that doughnuts, cookies, sodas, and candies were not included in the recommended carbohydrates. These unhealthy foods have a high glycemic index and drive hunger. Time honored evidence demonstrates that diets high in saturated fats are not healthy. We have learned about healthy fats such as monounsaturated and polyunsaturated oils which reduce cardiac risk factors.4 Finally, we know that ingesting protein with each meal is beneficial in reducing the glycemic index of carbohydrates resulting in less hunger and the tendency to eat less overall calories, the bottom line in weight loss and maintenance.

We live in a society with an unprecedented abundance and variety of food. People vary greatly in their food tastes. Promoting healthy nutrition requires flexibility in food choices. Understanding the basic principles of healthy carbohydrates, fats and proteins will go a long way in counteracting the epidemic of overweight and obesity. If people limited their food choices to healthy foods and kept active, we would not have today's epidemic obesity problem. This important study provides great reassurance and validation that the low fat diet recommendation is still valid, certainly in postmenopausal women.

References

1. Foster DG, et al. A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med. 2003;348: 2082-2090.

2. Samaha FF, et al. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med. 2003;348:2074-2081.

3. Brehm BJ, et al. A randomized trial comparing a very low carbohydrate diet and a calorie-restricted low fat diet on body weight and cardiovascular risk factors in healthy women. J Clin Endocrinol Metab. 2003;88: 1617-1623.

4. Appel LJ, et al. Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial. JAMA. 2005;294:2455-2464.