Nuts are a powerhouse food that contain a wealth of healthy fats, fiber, bioactive nutrients,and phytochemicals. They have been linked to several potential health benefits including decreasing risk of heart disease, diabetes, and hypertension, lowering cholesterol levels, and improving control of type 2 diabetes. Nuts may also play a role in decreasing inflammation and insulin resistance. However, some are concerned with the high fat contents in nuts. At least 50% of the calories in most nuts are made up of fats. Although these fats are good fats, they do increase the calorie value of nuts and may contribute to weight gain. Excess weight and obesity are factors that increase the risk of heart disease and diabetes which the nuts are hoped to help.
Spanish researchers set out to find more conclusive information of the effect of nuts on weight gain. A systematic review, published in the American Journal of Clinical Nutrition, found that nuts were not associated with an increase in body weight, waist circumference, or body mass index.
The systematic review included 33 randomized trials with adult participants who were offered a nut-enriched diet or their usual diet. Participants were assessed for changes in weight, body mass index (BMI), or waist circumference. A variety of nuts were used including almonds, cashews, pistachios, walnuts, peanuts and pecans. The nuts may have been used to replace other food items in the diet or simply added to current diet. Most studies lasted for 2-24 weeks.
When looking at body weight, BMI, and waist circumference, participants on the nut enriched diets did not have any differences compared to participants eating other diets.
A systematic review is considered a reliable method of research because it pools a large number of participants. The higher number of participants in a study, the more likely the results are to be true and not due to chance. Many of the studies were fairly short and any changes in weight may have been too small to be noticed. Longer term studies may help identify if nuts are linked to weight changes.
Some are scared off from nuts because they are a fatty, calorie-dense food but it appears adding them to your diet may not be hazardous to your waist after all. Additional studies also seem to support that nuts could be beneficial to your overall health. As with any food, moderation is an important factor. Consider nuts as a regular part of a well-balanced diet. Work with your doctor or dietitian to develop a diet plan if you have a chronic health condition or are at high risk of health issues like heart disease.
Flores-Mateo G, Rojas-Rueda D, et al. Nut Intake and Adiposity: Meta-analysis of Clinical Trials. Am J Clin Nutr. 2013 Jun;97(6):1346-55
Last reviewed June 2013 by Brian Randall, MD
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