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.
The Mediterranean diet was associated with reduced depression risk, but we found no evidence of such an association for the MIND diet.
Childhood obesity is associated with a greater chance of a lifetime of obesity. Evidence suggests dairy at recommended levels could be beneficial in maintaining normal weight and body composition. We assessed whether dairy consumption is associated with anthropometric indicators of health (z-scores for weight-for-age (WAZ); height-for-age (HAZ) and body mass index (BMIZ); waist-to-height ratio (WHtR); fat-free mass (FFM); and fat mass (FM)) in adolescents. In a cross-sectional study, 536 males and females ages 12–18 completed a 151-item semi-quantitative web-based food frequency questionnaire that included 34 dairy-containing foods. Dairy foods were categorized into milk, cheese, sweetened dairy, and total dairy. Anthropometrics were measured during school visits. Total dairy intake was associated with WAZ (β = 0.25 (95% CI: 0.01, 0.49), p = 0.045) and HAZ (β = 0.28 (95% CI: 0.04, 0.52), p = 0.021). In boys, total dairy was associated with WHtR (β = 0.02 (95% CI: 0.00, 0.04), p = 0.039), FFM (β = 4.83 (95% CI: 1.79, 7.87), p = 0.002), and FM (β = 3.89 (95% CI: 0.58, 7.21), p = 0.021), and cheese was associated with FFM (β = 4.22 (95% CI: 0.98, 7.47), p = 0.011). Dairy consumption seems to influence growth in both genders, and body composition and central obesity in boys. Prospective studies are needed to identify how types of dairy relate to growth, body composition, and central obesity of adolescents.
Objective: To validate a 171-item semi-quantitative food-frequency questionnaire (FFQ) for measurement of nutrient intake in an intervention trial based on walnut supplementation. Design and setting: Free-living adults from Southern California were randomly assigned to either an intervention (walnut-supplemented) or a control diet. The prescribed 6-month intervention was $ 28 g of walnuts per day for the walnutsupplemented group and # 2 g of walnuts per day for the control group. Participants provided at least six 24-hour dietary recalls and completed a self-administered FFQ. Subjects: Eighty-seven adults aged 30-72 years (48 females, 39 males). Results: Our findings from validation (by correlation with six diet recall measures) of the measurement of 32 nutrients by the FFQ are as follows. We found significant positive correlations (corrected for measurement error) between the FFQ and diet recalls for total energy (r ¼ 0.34), total carbohydrate (r ¼ 0.42), vegetable protein (r ¼ 0.43), total fat (r ¼ 0.51), polyunsaturated fat (r ¼ 0.77), total fibre (r ¼ 0.60), linoleic acid (r ¼ 0.78) and a-linolenic acid (r ¼ 0.79) -the last nutrient being an excellent nutrient biomarker of the intervention (walnut supplementation). Significant positive correlations were also found for vitamin C (r ¼ 0.96) and certain minerals (r ¼ 0.46 -0.80 for calcium, phosphorus, magnesium, iron and potassium). Uncorrected correlations were also high (r . 0.40) for retinol, b-carotene, folate and alcohol. Both diet recalls and FFQ showed a similar significant difference in a-linolenic acid content between the walnut-supplemented and control diets. Conclusions: The FFQ demonstrated good relative validity in the estimation intake of some of the major nutrients in a dietary intervention trial and was a particularly valid estimate of an important nutrient biomarker of walnut supplementation. In large-scale community-based intervention trials, the more precise methods of dietary assessment such as interviewer-based dietary recalls, food records or lengthy diet histories can be prohibitively expensive and carry a respondent burden that contributes to a high drop-out rate -particularly in underserved communities 9 . A practical and cost-effective alternative to diet recalls and diet histories is to assess dietary intake with a self-administered food-frequency questionnaire (FFQ). Numerous validation studies have shown that in a prospective cohort study, the FFQ can be a valid estimate of the food and nutrients measured by dietary recalls or diet histories 10 . To date, only a few studies have validated the use of the FFQ to assess baseline diet and dietary change (due to prescribed intervention) in an intervention trial 11 -15 .In the present study, we have conducted a validation analysis of data from a 6-month intervention trial that investigated the health effect of daily incorporation of walnuts into the habitual diet of free-living individuals. Dietary data were collected at baseline and during the follow-up by multiple 24-hour diet...
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