RESEARCH UPDATE: Does Eating Nuts Lead to Weight Gain, With or Without Guidance?
Results from a recent systematic review and meta-analysis suggest that that nuts, including almonds, may be consumed even in large quantities without changes in body weight or body composition, whether or not dietary substitution instructions are provided.1
While a number of clinical studies, including several on almonds, and meta-analytic reviews report that eating nuts will not cause weight gain, none considered the effect of varying dietary substitution instructions. Researchers at the University of Georgia were interested in determining if instructions provided on how to incorporate nuts into the diet might affect weight outcomes. They hypothesized that studies without substitution instructions would result in a significant increase in body weight, BMI, waist circumference (WC) and total body fat percentage (BF%), while studies that included calorie or fat substitution instructions would not result in these same increases.
Clinical trials using parallel or crossover design involving the daily consumption of nuts or nut-based snacks/meals by adults 18 years of age and older that ran for more than three weeks and reported on BW, BMI, WC, or BF% were reviewed. Each study was categorized by whether or not it contained dietary substitution instructions. In total, 55 studies were included in the meta-analysis. The researchers found that:
- In studies without dietary substitution instructions, there was no change in BW or BF%.
- In studies with dietary substitution instructions, there was no change in BW but there was a decrease in BF%. However, the BF% results should be interpreted with caution since only 5 studies were included in analysis that involved substitution instructions that reported BF%. Additionally, a variety of methods were used to measure BF% so the variability in precision and accuracy among these different measurement methods for body composition should be considered in interpretation of study results.
- There was no change in BMI or WC for either category of studies.
Limitations of this research included varying methodologies between included studies and the frequency of unreported outcome variables in excluded studies. A variety of nuts and dosages of nuts were used in the studies included in the meta-analysis. Click here to view the full study.