Nut consumption and weight gain

Nutrition Research Newsletter, Feb, 2007

Nuts are a central part of the Mediterranean food pattern (MFP), which includes a considerable intake of fat (up to 35% to 40% of total caloric intake). Adherence to a Mediterranean diet has resulted in protection against mortality for all causes and against the development of coronary heart disease, stroke, hypertension, and cancer. Nut consumption has also consistently shown an improvement in serum lipid and lipoprotein profiles. For this reason, the American Heart Association has recommended nut consumption since 2000. However, there is continued concern that an increase in consumption of this calorie-dense, high-fat food will lead to excessive weight gain.

In Europe, rates of obesity are higher in Mediterranean countries compared with Nordic countries. Therefore, there is the concern that nuts, as part of the MFP, could explain the obesity trend in the Mediterranean region. Current epidemiological evidence regarding this topic is limited and based mostly on indirect studies. A recent study from the University of Navarra in Spain examined the relationship between the frequency of nut consumption and the risk of weight gain (or becoming overweight/obese) in a Mediterranean cohort.

The SUN project (Seguimiento Universidad de Navarra) is a prospective cohort study of 8865 university graduates designed to establish associations between diet and the occurrence of several diseases and chronic conditions including obesity. Information such as medical history, health habits, lifestyle, and sociodemographic variables, were collected through self-administered questionnaires sent by mail every two years. Dietary habits were assessed with a validated semiquantitative FFQ. The subjects' weight was recorded at baseline and at least two years after baseline. Nine hundred thirty-seven subjects reported a weight gain of >5kg at follow-up time. Participants who ate nuts two or more times per week had a significantly lower risk of weight gain than those who never or almost never ate nuts. Participants with little nut consumption gained an average of 424 grams more than frequent nut eaters. 434 cases became overweight during the study from an initial 6300 nonoverweight subjects. Nut consumption was not significantly associated with incident overweight/obesity in the cohort.

The results show that frequent nut consumption was associated with a reduced risk of weight gain (5 kg or more). Therefore, this supports the current recommendation of nut consumption as an important component of a cardioprotective diet and also calms fears of possible weight gain. Since the results are from an observational study, a causal relationship cannot be proved. However, there are still many strengths of this study, which include its prospective design and the previous validation of the methods used to analyze the main variables.

Maria Bes-Rastrollo, Joan Sabate, and Enrique Gomez-Gracia. Nut Consumption and Weight Gain in a Mediterranean Cohort: The SUN Study. Obesity Research; 15:107-116 (January 2007). [Correspondence: Maria Bes Rastrollo, Department of Preventive Medicine and Public Health, University of Navarra, c/Irunlarrea, 1, 31008, Pamplona, Navarra, Spain. E-mail: mbes@unav.es.]