Moderate Fat Diet with Peanuts and Peanut Butter Keeps Weight Off Says Harvard Study

Oct 5, 2001

Researchers at Harvard School of Public Health and Brigham and Women’s Hospital in Boston have found that three times as many people were able to stick to a healthy moderate fat weight loss diet than those following the traditionally recommended low fat diet. Furthermore, they were able to keep the weight off for over 18 months, had better nutritional intakes and were more satisfied because they could eat some of their favorite foods each day such as peanut butter, nuts and healthy oils, in a healthy Mediterranean-style eating pattern. The landmark study was just released in the International Journal of Obesity.

Only one in five subjects could stick to the low fat diet versus more than half who stuck to the moderate fat diet. Both groups lost an average of 11 pounds in the first year. What makes this study revolutionary is that only the moderate fat group kept a significant amount of weight off for 18 months, whereas the low fat group did not. The moderate fat group was followed for an additional year (2 1/2 years total) and still kept a significant amount of weight off.

Half of the 101 overweight men and women in the study were instructed to eat a low fat diet (20% calories from fat) and half to eat a Mediterranean-style moderate fat diet (35% calories from fat, mostly monounsaturated from peanut butter, peanuts, mixed nuts, olive, canola and peanut oils). All participants were given dietary advice to eat a diet of approximately 1200-1500 calories that was low in saturated fat and cholesterol.

Kathy McManus, MS, RD, director of nutrition at Brigham and Women’s Hospital and coinvestigator of the study, says, “Any low calorie diet can work in the short run, but we need to know what kind of eating pattern can sustain long-term weight loss — which is key to preventing chronic disease. The subjects substituted high saturated fat foods, like butter, with healthy monounsaturated fat foods, like peanut butter. They tossed nuts on their salad instead of croutons and used small amounts of full fat salad dressings. My patients loved this diet because they could include favorite foods if they carefully watched portion sizes.”

Successful dieters in the Mediterranean-style moderate fat group increased peanut butter consumption by almost a serving (2 tablespoons) per day, increased peanut consumption by a half a serving (1/2 ounce or a small handful) and mixed nuts by almost a half a serving over their baseline diets. Other foods such as healthy oils (olive, peanut and canola) and avocados were added in small amounts. Surprisingly, those on the moderate fat diet increased consumption of vegetables by one serving per day. Intake of fiber, which most Americans don’t get enough of, was also increased significantly, and the moderate fat group tended to eat more protein compared to their baseline diets. In contrast, the low fat group decreased their consumption of vegetables and fiber compared to baseline.

One of the study’s success stories, Doralene Davis, of Boston, MA, is living proof that this can be a diet for life. She has now stuck with the healthy moderate fat diet for over two and a half years and has lost about 50 pounds and kept it off. She says, “I don’t feel deprived like I did in my past attempts at fad diets. This meal plan is easy to follow and I can still use it at restaurants and social gatherings. And, I can eat my favorite breakfast — peanut butter on whole wheat toast with bananas.”

Frank Sacks, MD, professor of cardiovascular disease prevention at Harvard School of Public Health and co-investigator of the study, says, “Our health care system will become bankrupt unless we can find a diet that will help Americans lose and kept weight off. Our study shows that this healthy moderate fat diet offers a successful alternative to the conventional low fat weight loss diet.” Experts agree that losing even 10 to 20 pounds can make a significant difference in disease prevention.

Despite decades of advice to the public to decrease total fat consumption, incidence of obesity is at epidemic levels in the U.S. and many other developed nations around the world. The Centers for Disease Control (CDC) estimates that over 60% of the adult U.S. population are overweight or obese. An increasing incidence of obesity is also on the rise for children. Overweight and obesity are associated with major chronic illnesses, including hypertension, heart disease, diabetes, arthritis, certain forms of cancer, and all-cause mortality.

Peanuts and peanut butter also contain fiber, vitamin E, folate, and many micronutrients important to health. Research studies have shown that peanuts and peanut butter can be part of a cholesterol-lowering diet and that they have a strong satiety value, keeping hunger at bay longer than some other low fat, high carbohydrate foods.

The Peanut Institute is a non-profit organization that supports nutrition research and develops educational programs to encourage healthful lifestyles.