Nuts are not thought of as one of the foods to eat to lose weight. Just the opposite, nuts are avoided because nuts are thought of as adding to weight gain. This is a shame because nuts are one of the high potassium foods that reduce blood pressure and increase bone density.
They also are composed of heart healthy fats, being mostly monounsaturated and polyunsaturated fats. The only nut with mostly carbohydrates is chestnuts. Because so many of their calories come from fat, one concern often expressed is whether eating nuts leads to weight gain. But lately a number of scientific studies have debunked the weight gain myth.
There have been several scientific studies that have examined weight gain from nuts. The largest and longest in duration is a recent study (1) that was done of 51,000 healthy women over 8 years. They asked the women how often they consumed nuts and examined their weight gain over the 8 years. Those women that ate the most nuts had the least weight gain and also had the lowest average weight and BMI. These findings confirmed the findings of a number of previous studies.
The previous studies were shorter studies lasting a few months and usually substituting only one specific nut, such as almonds or walnuts. Rather than do a food questionnaire like the present study, they had the participants substitute the nut for other food in their diet for a few months. These studies also showed no increased weight gain in those who ate nuts.
The present study examined tree nuts and peanuts in the diet. The researchers found that neither peanuts nor other nuts caused increased weight gain in the study participants. This study did not artificially start the women on nuts, but instead looked at what they had been eating normally. The women were then divided into groups according to how often they ate nuts.
The researchers were able to follow the women's diet for 8 years. There were some other differences among the women besides how often they ate nuts. The women who ate nuts more than 2 times a week were more physically active, ate more calories and differed in several other ways from the women who ate fewer nuts. Because of this, the study adjusted the numbers for confounding conditions and still found those who ate nuts had less weight gain than those who did not.
Even with the correction for confounders, the women did not gain weight as expected. One possible explanation is that the nuts do not contribute as many calories as expected because they are not fully chewed and some calories pass through without being absorbed. Multiple other studies have shown the calories you would expect to be absorbed from nuts are not absorbed.
Nuts are a part of several healthy diets, such as the high potassium foods diet and the Mediterranean diet, contributing essential fats and some protein. This study is the largest to show that nuts as part of a healthy diet can help prevent or slow weight gain. They should not be avoided because of the fear of weight gain. Next week we will discuss some studies that used nuts in a weight loss diet.
To find tables of potassium values and the macronutrient content of nuts look here. For other foods, the list of posts also has links to posts with tables of food values listed.
1. Prospective study of nut consumption, long-term weight change, and obesity risk in women. Bes-Rastrollo M, Wedick NM, Martinez-Gonzalez MA, Li TY, Sampson L, Hu FB. Am J Clin Nutr. 2009 Jun;89(6):1913-9. Epub 2009 Apr 29.