New Study Says Don’t Go Too Low-Fat on a Weight-Loss Diet

Jan 29, 2004

Higher unsaturated-fat, lower-carb diet with peanuts and peanut butterhelps heart and waistline too

New research shows that a higher unsaturatedfat, peanut-rich, weight-loss diet reduces the risk of cardiovascular disease by 14% compared to baseline, whereas a low-fat diet does not. This ground– breaking study, published in the February issue of American Journal of Clinical Nutrition, proves that the way you lose weight is important for long-term health. Penny Kris-Etherton, PhD, RD, principal investigator and distinguished professor of nutrition at The Pennsylvania State University, says, “In this study, the peanutrich, higher-unsaturated fat diet resulted in favorable heart-health benefits. The low-fat group, in contrast, lowered the “good” HDL cholesterol and showed a rebound in triglycerides during weight maintenance.” Dr. Kris-Etherton continues, “Overall, the peanut-rich diet reduced the risk of cardiovascular disease by 14% compared to baseline.”

Participants in both the low-fat group and the higher unsaturated-fat group lost 2.5 pounds per week during the weight-loss phase, and lowered total and “bad” low-density lipoprotein (LDL) cholesterol. However, during the weight maintenance phase, those on the higher unsaturated-fat, peanut and peanut butter diet had the added cardiovascular benefit of maintaining “good” highdensity (HDL) cholesterol and lowering triglyceride levels, both important risk factors for heart disease. The low-fat diet saw a significant drop in good HDL cholesterol levels.

In addition, this is the first study to show that, even with weight-loss, a low-fat diet did not favorably affect triglyceride levels. The low-fat group saw triglycerides rebound to pre-weight loss levels during weight maintenance. Low-fat diets, often recommended for weight-loss, are higher in carbohydrates, and therefore, tend to raise trigylceride levels.

Further, the higher-fat, peanut and peanut butter diet group saw a favorable drop in the ratios of their “bad” cholesterol to “good” cholesterol. Conversely, there was no change in these important ratios in the low-fat group. Scientists think that measuring cholesterol ratios may be a more comprehensive risk assessment tool than looking at LDL cholesterol alone.

Fifty-three overweight and obese adults participated in the 10-week controlled clinical trial. Half consumed a higher unsaturated-fat diet (33% of calories from fat, half from peanut products) and half consumed a low-fat diet (18% of calories from fat). The higher unsaturated-fat diet contained 17% of calories from protein and 50% of calories from carbohydrate. The low-fat diet contained a similar amount of protein (18% of calories) and 64% of calories from carbohydrate. Both diets were low in saturated fat (less than 7%) and cholesterol (approximately 200 mg), consistent with the National Cholesterol Education Program Guidelines.

Although a low-fat diet has been recommend for weight-loss for the past 20 years, newer research shows that a calorie-controlled, higher unsaturated-fat diet may produce better weight-loss results. In a recent study at Harvard, 101 people followed one of two diets — one low in fat (20% of energy from fat) or one moderate in fat (35% of energy from fat, mainly unsaturated fat).

At the end of the Harvard study, researchers found that three times as many people were able to stick to a higher unsaturated-fat weight-loss diet versus the traditionally recommended low-fat diet. The dieters in the higher unsaturated-fat group were able to keep the weight off for two and a half years, had better nutritional intakes and were more satisfied because they could eat some of their favorite foods each day such as peanut butter, nuts, peanuts and healthy oils.

It’s not the “all-the-fat-you-can-eat” Atkins diet, which allows up to 20% of total calories from saturated fat — far exceeding current dietary recommendations for less than 7%. Nor is it the severely fat-restrictive Dean Ornish plan that provides less than 10% of calories from total fat, which is far from palatable. Rather, this peanut-rich diet is a truly balanced diet that provides a healthy range of “good,” unsaturated fat, carbohydrate, fiber, and protein, that also allows satisfying foods such as peanut butter. More importantly, it helped study participants achieve weight loss and reap cardiovascular benefits.

Peanuts and peanut butter contain important nutrients such as vitamin E, folate, fiber, magnesium, potassium, zinc, and phytosterols, and are naturally low in carbohydrate. Peanuts and peanut butter contain 2 grams of fiber and just 4 grams of “net carbs” (total carbohydrate minus fiber) per serving.

This study was funded by the Peanut Institute.