Studies consistently show the beneficial effects of eating nuts, but as high-energy foods, their regular consumption may lead to weight gain. We tested if daily consumption of walnuts (approximately 12 % energy intake) for 6 months would modify body weight and body composition in free-living subjects. Ninety participants in a 12-month randomized cross-over trial were instructed to eat an allotted amount of walnuts (28-56 g) during the walnut-supplemented diet and not to eat them during the control diet, with no further instruction. Subjects were unaware that body weight was the main outcome. Dietary compliance was about 95 % and mean daily walnut consumption was 35 g during the walnut-supplemented diet. The walnut-supplemented diet resulted in greater daily energy intake (557 kJ (133 kcal)), which should theoretically have led to a weight gain of 3·1 kg over the 6-month period. For all participants, walnut supplementation increased weight (0·4 (SE 0·1) kg), BMI (0·2 (SE 0·1) kg/m 2 ), fat mass (0·2 (SE 0·1) kg) and lean mass (0·2 (SE 0·1) kg). But, after adjusting for energy differences between the control and walnut-supplemented diets, no significant differences were observed in body weight or body composition parameters, except for BMI (0·1 (SE 0·1) kg/m 2 ). The weight gain from incorporating walnuts into the diet (control ! walnut sequence) was less than the weight loss from withdrawing walnuts from the diet (walnut ! control sequence). Our findings show that regular walnut intake resulted in weight gain much lower than expected and which became non-significant after controlling for differences in energy intake.

Consumption of both nuts increased plasma polyphenol concentrations, increased the total antioxidant capacity and reduced plasma lipid peroxidation.

Background/Objectives: Walnuts have been shown to reduce serum lipids in short-term well-controlled feeding trials. Little information exists on the effect and sustainability of walnut consumption for longer duration in a free-living situation. Subjects/Methods: A randomized crossover design in which 87 subjects with normal to moderate high plasma total cholesterol were initially assigned to a walnut-supplemented diet or habitual (control) diet for a 6-month period, then switched to the alternate dietary intervention for a second 6-month period. Each subject attended seven clinics 2 months apart. At each clinic, body weight was measured, and in five clinics (months 0, 4, 6, 10 and 12), a blood sample was collected. Results: Our study showed that supplementing a habitual diet with walnuts (12% of total daily energy intake equivalent) improves the plasma lipid profile. This beneficial effect was more significant in subjects with high plasma total cholesterol at baseline. Significant changes in serum concentrations of total cholesterol (P ¼ 0.02) and triglycerides (P ¼ 0.03) were seen and nearly significant changes in low-density lipoprotein cholesterol (LDL-C) (P ¼ 0.06) were found. No significant change was detected in either high-density lipoprotein (HDL) cholesterol LDL to HDL ratio. Conclusions: Including walnuts as part of a habitual diet favorably altered the plasma lipid profile. The lipid-lowering effects of walnuts were more evident among subjects with higher lipid baseline values, precisely those people with greater need of reducing plasma total and LDL-C.