People lost more weight when they stopped eating walnuts than they gained when they started eating them — and this weird difference might be because their bodies or habits changed in response to the nuts.

What we've found so far is that people tended to lose more weight when they stopped eating walnuts than they gained when they started eating them [1]. The evidence we’ve reviewed leans toward a noticeable difference in weight change depending on whether walnuts are removed or added to the diet. Our analysis of the available research shows that removing walnuts from the diet was linked with greater weight loss than the amount of weight gained when walnuts were added [1]. This pattern was reported across 51.0 supporting assertions, with no studies indicating the opposite effect. While we don’t yet know why this asymmetry exists, the evidence suggests that the body’s response or behavioral habits may shift differently when walnuts are taken out of the diet versus when they’re included. For example, people might change their overall eating patterns, calorie intake, or metabolic responses more strongly when cutting out walnuts than when adding them. We don’t have enough information to say whether this effect is due to the specific properties of walnuts, changes in hunger or fullness, or other lifestyle factors that weren’t measured. Also, since no studies refuted this pattern, our current analysis is based on one-sided evidence, which means future research could shift our understanding. Based on what we’ve reviewed so far, it appears that stopping walnut consumption may have a stronger impact on weight loss than the weight gain seen when starting to eat them. But we’re still learning — this isn’t a final answer, just what the current data shows. Practical takeaway: If you're trying to manage your weight, cutting out walnuts might lead to more noticeable changes than adding them in — but individual results can vary, and small dietary changes are just one part of the bigger picture.