Body Composition Across the Adult Lifespan in African Caribbean Men: The Tobago Longitudinal Study of Aging.

Body composition and muscle strength change vary by age and ethnicity, and have a major impact on health and physical function. Little is known about the patterns of these changes in African-ancestry populations. Herein, we examined age-specific (5-year age groups) rates-of-change in lean and fat mass in 1918 African-ancestry men on the Caribbean island of Tobago (baseline age: 62.0±11.8 years, range: 40-99 years). Body composition (DXA) and grip strength were measured at three time points (baseline, 4- and 9-year follow-up). Annualized rates of change were calculated with all 3 time-points using Generalized Estimating Equations. We found that whole body lean mass declined at constant rate until age 65 (-0.72%/year; 95% CI: -0.76, -0.67), which accelerated to -0.92 %/year (-1.02, -0.82) among those 65-69, and again to -1.16 %/year (-1.30, -1.03 ) among those aged 70+. Whole body fat mass increased by a near constant rate of 2.93 %/year (2.72, 3.15%) across the lifespan. Finally, grip strength decline accelerated at age 50, and about 2x faster than lean mass through the lifespan after the age of 50. To conclude, in African-Caribbean men, the acceleration in muscle strength decline precedes the acceleration in lean mass decline by 10-15 years, suggesting decrements in factors other than lean mass drive this initial acceleration in muscle strength decline. We also found that African-Caribbean men undergo a constant shift to a more adipogenic phenotype throughout the adult lifespan (aged 40-99), which likely contributes to age-related loss of muscle and physical function.

Transition to a More even Distribution of Daily Protein intake Is Associated with Enhanced Fat Loss during a Hypocaloric and Physical Activity Intervention in Obese Older Adults.

BACKGROUND: Optimization of intentional weight loss in obese older adults, through preferential fat mass reduction, is challenging, as the concomitant lean mass loss may exacerbate sarcopenia. Recent studies have suggested within-day distribution of protein intake plays a role in determining body composition remodeling. Here, we assessed whether changes in within-day protein intake distribution are related to improvements in body composition in overweight/obese older adults during a hypocaloric and exercise intervention. METHODS: Thirty-six community-dwelling, overweight-to-obese (BMI 28.0-39.9 kg/m2), sedentary older adults (aged 70.6±6.1 years) were randomized into either physical activity plus successful aging health education (PA+SA; n=15) or physical activity plus weight loss (PA+WL; n=21) programs. Body composition (by CT and DXA) and dietary intake (by three-day food records) were determined at baseline, 6-month, and 12-month follow-up visits. Within-day protein distribution was calculated as the coefficient of variation (CV) of protein ingested per defined time periods (breakfast [5:00-10:59], lunch [11:00-16:59] and dinner [17:00-1:00]). Secondary analysis was performed to determine associations between changes in protein intake distribution and body composition. RESULTS: In both groups, baseline protein intake was skewed towards dinner (PA+SA: 49.1%; PA+WL: 54.1%). The pattern of protein intake changed towards a more even within-day distribution in PA+WL during the intervention period, but it remained unchanged in PA+SA. Transition towards a more even pattern of protein intake was independently associated with a greater decline in BMI (P<0.05) and abdominal subcutaneous fat (P<0.05) in PA+WL. However, changes in protein CV were not associated with changes in body weight in PA+SA. CONCLUSION: Our results show that mealtime distribution of protein intake throughout the day was associated with improved weight and fat loss under hypocaloric diet combined with physical activity. This finding provides a novel insight into the potential role of within-day protein intake on weight management in obese older people.

Serum Vitamin D and Age-Related Muscle Loss in Afro-Caribbean Men: The Importance of Age and Diabetic Status.

BACKGROUND: Prospective studies examining the potential association of vitamin D with age-related muscle loss have shown inconsistent results. OBJECTIVE: To examine the association between baseline serum 25-hydroxyvitamin D (25(OH)D), 1,25-dihydroxyvitamin D (1,25(OH)2D), and prospective change in lean mass with aging in African ancestry population. We also determined if associations were modulated by age and diabetes mellitus (DM). DESIGN: Prospective observational cohort study. SETTING: Data were collected from a random sub-sample of 574 men, participants of the Tobago Bone Health Study (TBHS). PARTICIPANTS: 574 Afro-Caribbean men, aged 43+ years (mean age: 59.1 ± 10.5), who were randomly selected as the participants in both the baseline and the follow-up visits. MEASUREMENTS: Baseline fasting serum 25(OH)D was measured using liquid chromatography mass spectrometry (LC-MS/MS), and and 1,25(OH)2D was measured using radioimmunosassay (RIA). Changes in dual-energy X-ray absorptiometry (DXA)-measured appendicular lean mass (ALM), and total body lean mass (TBLM) were measured over an average of 6.0 ± 0.5 years. The associations of 25(OH)D and 1,25(OH)2D with ALM and TBLM were assessed by multiple linear regression model after adjusting for potential confounders. RESULTS: When stratifying all men into two groups by age, greater baseline 25(OH)D and 1,25(OH)2D levels were associated with smaller losses of ALM and TBLM in older (age 60+ years) but not in younger (age 43 - 59 years) men. When stratifying by DM status, the associations of 25(OH)D and 1,25(OH)2D with declines in ALM and TBLM were statistically significant only in prediabetic, but not among normal glycemic or diabetic men. CONCLUSION: Higher endogenous vitamin D concentrations are associated with less lean mass loss with aging among older and prediabetic Afro-Caribbean men independent of potential confounders. Our findings raise a possibility that maintaining high serum vitamin D level might be important for musculoskeletal health in elderly and prediabetic African ancestry men.

Effects of Changes in Regional Body Composition on Physical Function in Older Adults: A Pilot Randomized Controlled Trial.

BACKGROUND/OBJECTIVE: Obesity exacerbates age-related physical disability; however, observational studies show that any weight loss in old age is associated with greater risk of mortality. Conversely, randomized controlled trials in older adults show that weight loss is beneficial. The discrepancy may be due to weight loss intention and differential changes to regional body composition. The purpose of this research was to evaluate the independent role of regional body composition remodeling in improving physical function. DESIGN: Pilot Randomized Controlled Trial. SETTING: Community based research center. PARTICIPANTS: Thirty-six community dwelling, overweight to moderately obese (BMI 28.0-39.9 kg/m2) older adults (age 70.6±6.1 yrs). INTERVENTION: Physical activity plus weight loss (PA+WL, n=21) or PA plus successful aging (SA) education. PA consisted primary of treadmill walking supplemented with lower extremity resistance and balance training. The WL program was based on the Diabetes Prevention Project and aimed at achieving a 7% weight loss by cutting calories, specifically those from fat. MEASUREMENTS: At baseline, 6- and 12-months, body composition was measured using computerized tomography and dual x-ray absorptiometry. Abdominal visceral (VAT) and thigh intermuscular (IMAT) adipose tissue were quantified. Physical function was assessed using the short physical performance battery (SPPB). RESULTS: Separate multivariable linear regression models with both groups combined demonstrated that decreases in IMAT and VAT were significantly associated with improvements in SPPB (P<0.05) independent of change in total fat mass. PA+WL improved SPPB scores from baseline (0.8±1.4, P<0.05), whereas PA+SA did not; however no intergroup difference was detected. Of note, these effects were mainly achieved during the intensive intervention phase. CONCLUSION: Decreases in IMAT and VAT are important mechanisms underlying improved function following intentional weight loss plus physical activity.