Eating walnuts doesn’t make adults gain weight over several weeks—even though they’re high in calories, studies show no real change in weight or BMI.

What we've found so far is that eating walnuts does not appear to lead to weight gain in adults over periods of 4 to 24 weeks, despite their high calorie content [1]. Our analysis of the available research shows no meaningful changes in body weight or BMI when walnuts are added to the diet. We reviewed one assertion based on existing studies, and it indicates that even though walnuts are calorie-dense, including them in the diet does not result in weight gain over several weeks [1]. This finding comes from research involving adults who consumed walnuts as part of their regular eating patterns for 4 to 24 weeks. The evidence we've reviewed leans toward the idea that walnuts may fit into a balanced diet without increasing the risk of short-term weight gain [1]. It’s important to note that this is based on limited data—only one assertion was analyzed, supported by 67.0 studies, with no studies refuting the claim. While the number of supporting studies appears high, we can’t assess the quality or design of those studies from this information alone. Our current analysis does not rule out the possibility that longer-term effects or different dietary contexts could lead to different outcomes. We also don’t yet have enough evidence to say how walnuts might affect weight beyond 24 weeks, or how they compare to other calorie-dense foods. There may be factors like overall diet, activity level, or portion size that influence results, but our current review doesn’t address those in detail. The takeaway: Based on what we’ve reviewed so far, adding walnuts to your diet for several weeks is not linked to weight gain in adults—even though they’re high in calories. This doesn’t mean walnuts cause weight loss or can be eaten without limit, but they may be a satisfying, nutritious addition without tipping the scale upward in the short term.