Eating a small handful of walnuts every day for a month might help shrink your waist a little bit if you're a middle-aged white adult at risk for metabolic problems and not on medication.

What we've found so far suggests that eating about 45 grams of walnuts daily for 4 weeks may be linked to a small reduction in waist size among middle-aged Caucasian adults at risk for metabolic syndrome who are not taking medication [1]. Our analysis of the available evidence shows this pattern, but we are still building our understanding. We looked at 46 supporting assertions and found no studies that contradict this idea [1]. The evidence we’ve reviewed leans toward a possible benefit of daily walnut consumption on waist measurement in this specific group. However, we don’t yet know how strong or consistent this effect is across different people or settings. Since all the data we analyzed come from the same type of population—middle-aged, white, and not on medication—our findings may not apply to other groups. We also don’t have details on how much the waist size changed, whether the results lasted beyond four weeks, or what might be driving the change—whether it’s due to the walnuts themselves or other shifts in diet or lifestyle. Because of this, we can’t say for sure what’s causing the change, only that the current evidence points in this direction. Our current analysis shows a consistent signal in one specific context, but we need more information to understand the full picture. As we review more studies over time, our understanding may shift. Practical takeaway: If you're a middle-aged white adult at risk for metabolic issues and not on medication, adding a small handful of walnuts to your daily diet might make a small difference in your waist size after a month—but don’t expect dramatic changes, and keep in mind that this is just one piece of what could support overall health.