Circulating 25-Hydroxyvitamin D Concentrations in Overweight and Obese Adults Are Explained by Sun Exposure, Skin Reflectance, and Body Composition.

BACKGROUND: Obese individuals are known to be at higher risk for vitamin D deficiency than normal-weight individuals. Cutaneous synthesis is a major source of vitamin D; however, objective measurements of sun exposure are lacking in this population. OBJECTIVE: To assess the validity of a regression model using sun exposure in lean individuals to estimate serum 25-hydroxyvitamin D [25(OH)D] in overweight and obese individuals, and to develop a prediction equation for serum 25(OH)D in overweight and obese adults. METHODS: This study was a secondary analysis of a 15-wk controlled feeding study investigating the effects of dairy consumption on body composition. Information regarding sun exposure, including day, hour, time outside, and clothing, were self-assessed in sun exposure diaries. Personal sun exposure energy (joules) was assessed by downloading time-specific ultraviolet B energy data from climate stations. Skin reflectance was measured using a Minolta 2500d spectrophotometer. Dietary intake of vitamin D was known. Serum 25(OH)D concentration was measured by radioimmunoassay. Body composition was determined from whole-body dual energy x-ray absorptiometry and computed tomography scans. RESULTS: Sun exposure was positively related to serum 25(OH)D (r = 0.26; P ≤ 0.05) and inversely related to total fat mass, android fat, and BMI (r = -0.25, -0.30, and -0.32, respectively). The modified Hall model significantly overestimated serum 25(OH)D in overweight and obese adults by 27.33-80.98 nmol/L, depending on the sun exposure calculation. A new regression model was developed for overweight and obese persons that explained 29.1% of the variance in postintervention 25(OH)D concentrations and included sun exposure, skin reflectance, total fat mass, total lean mass, and intra-abdominal adipose tissue as predictors. CONCLUSION: Major determinants of serum 25(OH)D concentration in healthy overweight and obese individuals include sun exposure, skin reflectance, and adiposity. Addition of adiposity terms to the prior model significantly improved predictive ability in overweight and obese men and women. (clinicaltrials.gov: NCT00858312).

Influence of race, acculturation, and socioeconomic status on tendency toward overweight in Asian-American and Mexican-American early adolescent females.

BACKGROUND: Health disparities in chronic disease prevalence exist in the United States among racial/ethnic groups. This study explores relationships between physical, socioeconomic, and cultural characteristics of a multi-ethnic sample of early adolescent females which may assist health educators in designing programs targeting these groups. METHODS: Mexican-American and Asian-American sixth grade females (n = 144) were enrolled in Adequate Calcium Today. Physical measurements included weight, height, and BMI. Dual energy X-ray absorptiometry determined percent body fat (%BF). Socioeconomic status was determined by enrollment in free or reduced meal program (FRMP). An adapted Acculturation Rating Scale for Mexican-Americans-II (ARSMA-II) measured acculturation. RESULTS: Mexican-Americans had greater height, BMI, %BF, and a greater tendency toward overweight (P < 0.01) than Asian-American. Asian-Americans were more acculturated than MA (P < 0.005), attributed to a lower ethnic orientation scale score. Within Asian-Americans, %BF was higher among FRMP participants than non-participants (P < 0.05). DISCUSSION: Income and acculturation may affect tendency toward chronic disease.

Additional zinc delivered in a liquid supplement, but not in a fortified porridge, increased fat-free mass accrual among young Peruvian children with mild-to-moderate stunting.

The exact mechanism whereby zinc influences growth is unknown, although it has been postulated that zinc may stimulate appetite and energy intake or enhance fat-free mass (FFM) accrual directly. We compared energy intake, reported appetite, and body composition of 6- to 8-mo-old Peruvian children with initial length-for-age Z-score (LAZ) < -0.5 SD who were randomly assigned to receive daily for 6 mo: 1) 3 mg/d zinc in a liquid supplement; 2) 3 mg/d zinc in a fortified porridge; or 3) no extra zinc in either the supplement or porridge. There were no group-wise differences in changes in dietary energy intakes or body composition or in the prevalence of reported poor appetite. However, among children with an initial LAZ less than the median (-1.1 SD), those who received zinc as a liquid supplement had a 0.41 kg greater increase in FFM than those who did not receive zinc (P < 0.05). We concluded that daily provision of 3 mg of supplemental zinc did not affect energy intake or reported appetite. Among children with initial mild-to-moderate stunting, those who received the zinc supplement had a greater increase in FFM than those who did not receive additional zinc. It is possible that the growth-restricted children were more likely to be zinc deficient and that FFM accrual may be an early growth response to supplemental zinc. Zinc supplements may be more efficacious than the same dose of zinc provided in fortified food; therefore, further research is needed on the optimal level of zinc fortification that will result in improved health outcomes in populations with high rates of zinc deficiency.

Longitudinal measures of circulating leptin and ghrelin concentrations are associated with the growth of young Peruvian children but are not affected by zinc supplementation.

BACKGROUND: Leptin, ghrelin, and insulin are hormonal regulators of energy balance and, therefore, may be related to growth during infancy. Zinc is essential for growth, and its growth effects may be mediated through these hormones. OBJECTIVE: We examined the effects of supplemental zinc on plasma leptin, ghrelin, and insulin concentrations among young children at risk of zinc deficiency and examined the relations between these hormones and physical growth. DESIGN: Children (n = 142) aged 6-8 mo were randomly assigned to receive 3 mg Zn/d as a supplement, in a fortified food, or as a placebo for 6 mo. Relations between hormones and anthropometric z scores, body composition, and growth rates were examined at baseline and 3 and 6 mo after the start of the intervention. RESULTS: No treatment group-related differences were found in plasma leptin, ghrelin, or glucose concentrations or in anthropometric z scores at 3 or 6 mo after the start of the zinc intervention. Neither plasma leptin nor ghrelin concentrations at baseline or 3 mo were predictive of subsequent changes in growth. However, changes in weight-for-age z scores over the two 3-mo time intervals were positively associated with subsequent leptin concentrations and inversely associated with subsequent plasma ghrelin concentrations. CONCLUSIONS: Supplemental zinc did not affect the children's growth, anthropometric indexes, or plasma hormone concentrations in this study population. Our results suggest that plasma leptin and ghrelin concentrations in later infancy are a consequence of previous weight changes rather than predictors of short-term growth.