Many Paths to Successful Weight Loss
Low-fat, low-carb, and Mediterranean diets yield similar results.
“What’s the best way to lose weight?” is one of life’s persistent questions. A low-fat, lower-calorie diet has long been heralded as the one true way to shed pounds. That works for some people, but not for others—actually, not for many others. New results from a large, long,head-to-head comparison, published in the July 17, 2008, New England Journal of Medicine, shows that a low-carbohydrate approach or a Mediterranean-type eating pattern are just as good as a low-fat diet for losing weight. (1) They may also be better for preventing or controlling heart disease and diabetes.
- Low fat diet: Focus on low-fat grains, vegetables, fruits, and beans; limit additional fats, sweets, high-fat snacks. Targets: 1500 calories a day for women, 1800 for men; under 30% of daily calories from fat, under 10% from saturated fat.
- Low carb diet: Focus on vegetarian sources of protein and fat; avoid trans fats; no set limit on calories. Targets: Under 20 grams of carbohydrates daily for the first two weeks, under 120 grams a day thereafter.
- Mediterranean diet: Focus on fruits, vegetables, whole grains; poultry and fish instead of red meat; added olive oil and nuts to increase intake of unsaturated fats. Targets: 1500 calories a day for women, 1800 for men; under 35% of daily calories from fat.
For the Dietary Intervention Randomized Controlled Trial (DIRECT), researchers recruited 322 men and women who worked for the same company in Israel.Each volunteer had a body-mass index (BMI) above 30, putting them in the obese category. One-third of the volunteers were assigned to a low-fat diet, one-third to a low-carb diet, and one-third to a Mediterranean-style diet. They ate lunch—the main meal in Israel—in the workplace cafeteria, which served meals appropriate for each of the three diets. They regularly met with dietitians. And they were encouraged to exercise and make other healthy changes.
The Atkins Foundation provided partial funding for the study through an investigator-initiated grant, which ran for two years. The foundation had no influence on the study design, conduct, analysis, or reporting of the results, says Dr. Meir Stampfer, professor of nutrition and epidemiology at Harvard School of Public Health, who was the senior DIRECT investigator.
After two years, average weight loss was 6.4 pounds with the low-fat diet, 9.7 pounds with the Mediterranean diet, and 10.3 pounds with the low-carb diet. The average was even higher for the volunteers who were still following their diets at the end of the study. Most of the weight loss happened in the first six months.
There were other important differences between the three diets. The volunteers following the low carb diet had the biggest drops in triglycerides, the main fat-carrying particle in the bloodstream, and the biggest increases in protective HDL cholesterol. Both of those changes would be expected to protect against heart disease. Those following the Mediterranean diet showed the biggest reduction in low-grade inflammation, a process linked to the development of heart disease. Among the volunteers with diabetes, the Mediterranean diet yielded better fasting blood sugar and insulin than the other two diets.
What is a “Mediterranean” Diet?
There’s no such thing as the Mediterranean diet. Foods, eating patterns, and lifestyle in the countries that border the Mediterranean Sea differ. But there are similarities that define a Mediterranean eating pattern. These include the following:
- Fruits, vegetables, grains, beans, nuts, and seeds (minimally processed, seasonally fresh, and grown locally) are eaten daily and make up about half of the diet.
- Fats, mostly unsaturated fat from olive oil, may account for up to 40% of daily calories.
- Cheese or yogurt are usually eaten each day.
- Fish, poultry, or eggs are eaten more often than red meat.
- Small amounts of red wine are typically taken with meals.
- Dessert is usually fresh fruit; sweets containing sugars and honey are treats.
- Regular physical activity is a part of daily life.
DIRECT adds to the mounting evidence that there are several paths to weight loss. A handful of trials have shown that low-carb and low-fat diets both work in the long run, though the low carb approach yields somewhat faster weight loss. (2-5) The Mediterranean diet has been shown to help prevent or treat heart disease, (6, 7) but its effect on weight loss hasn’t been settled.(8) The DIRECT results are important because the study lasted two years and most (85%) of the volunteers stuck with their diets throughout the study. Earlier studies lasted just six months to one year, and up to half of participants dropped out.
The lesson from DIRECT is not that low-carb or Mediterranean-type diets are better than low-fat diets, though you will undoubtedly see that spin in some media reports and ads for Atkins and South Beach diets. “The key message is that you have choices when it comes to losing weight,” says Dr. Stampfer.
Different people respond differently to different diets. If you give a particular diet your best shot and it doesn’t work, it’s possible that it wasn’t right for what you like to eat, how you like to eat,your metabolism, or your social situation. “If one diet approach isn’t working well for you, try another instead of giving up,” advises Dr.Stampfer.
1. Shai I, Schwarzfuchs D, Henkin Y, et al. Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet. N Enl J Med. 2008; 359:229-41.
2. Gardner CD,Kiazand A, Alhassan S, et al. Comparison of the Atkins, Zone, Ornish, and LEARNdiets for change in weight and related risk factors among overweightpremenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007; 297:969-77.
3. Brehm BJ, Seeley RJ, Daniels SR,D’Alessio DA. A randomized trial comparing a very low carbohydrate diet and acalorie-restricted low fat diet on body weight and cardiovascular risk factorsin healthy women. J Clin Endocrinol Metab.2003; 88:1617-23.
4. Foster GD, Wyatt HR, Hill JO, et al.A randomized trial of a low-carbohydrate diet for obesity. N Engl J Med. 2003; 348:2082-90.
5. Dansinger ML, Gleason JA, GriffithJL, Selker HP, Schaefer EJ. Comparison of the Atkins, Ornish, Weight Watchers,and Zone diets for weight loss and heart disease risk reduction: a randomizedtrial. JAMA. 2005; 293:43-53.
6. Tuttle KR, Shuler LA, Packard DP, etal. Comparison of low-fat versus Mediterranean-style dietary intervention afterfirst myocardial infarction (from The Heart Institute of Spokane DietIntervention and Evaluation Trial). Am JCardiol. 2008; 101:1523-30.
7. de Lorgeril M, Salen P, Martin JL,Monjaud I, Delaye J, Mamelle N. Mediterranean diet, traditional risk factors,and the rate of cardiovascular complications after myocardial infarction: finalreport of the Lyon Diet Heart Study. Circulation.1999; 99:779-85.
8. Malik VS, Hu FB. Popular weight-lossdiets: from evidence to practice. NatClin Pract Cardiovasc Med. 2007; 4:34-41.
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