1.
Joint association between body fat and its distribution with all-cause mortality: A data linkage cohort study based on NHANES (1988-2011).
Dong, B, Peng, Y, Wang, Z, Adegbija, O, Hu, J, Ma, J, Ma, YH
PloS one. 2018;13(2):e0193368
-
-
-
Free full text
Plain language summary
Recent findings suggest both underweight and obesity based on body mass index (BMI) were associated with the increased risk of mortality. As BMI cannot discriminate between lean mass and body fat mass, it is unclear whether the amount and distribution of body fat impacts mortality risk. Therefore, the aim of this study was to assess whether fat distribution confers any additional risk of mortality in addition to fat amount. This data linkage cohort study included 16415 participants aged 18 to 89 from the National Health and Nutrition Examination Survey (NHANES) and its linked mortality data. A total of 4999 deaths occurred during the 19-year follow up and body fat percentages were estimated based on bioelectrical impedance analysis and waist-hip ratio (WHR). This study showed both body fat percentage and WHR are independently associated with mortality. Based on these findings the authors conclude both the amount of body fat and its distribution should be considered with assessing all-cause mortality risk.
Abstract
OBJECTIVE Although obesity is recognized as an important risk of mortality, how the amount and distribution of body fat affect mortality risk is unclear. Furthermore, whether fat distribution confers any additional risk of mortality in addition to fat amount is not understood. METHODS This data linkage cohort study included 16415 participants (8554 females) aged 18 to 89 years from National Health and Nutrition Examination Survey III (1988-1994) and its linked mortality data (31 December 2011). Cox proportional hazard models and parametric survival models were used to estimate the association between body fat percentage (BF%), based on bioelectrical impedance analysis, and waist-hip ratio (WHR) with mortality. RESULTS A total of 4999 deaths occurred during 19-year follow-up. A U-shaped association between BF% and mortality was found in both sexes, with the adjusted hazard ratios for other groups between 1.02 (95% confidence interval: 0.89, 1.18) and 2.10 (1.47, 3.01) when BF% groups of 25-30% in males and 30-35% in females were used as references. A non-linear relationship between WHR and mortality was detected in males, with the adjusted hazard ratios among other groups ranging from 1.05 (0.94, 1.18) to 1.52 (1.15, 2.00) compared with the WHR category of 0.95-1.0. However in females, the death risk constantly increased across the WHR spectrum. Joint impact of BF% and WHR suggested males with BF% of 25-30% and WHR of 0.95-1.0 and females with BF% of 30-35% and WHR <0.9 were associated with the lowest mortality risk and longest survival age compared with their counterparts in other categories. CONCLUSIONS This study supported the use of body fat distribution in addition to fat amount in assessing the risk of all-cause mortality.
2.
Efficacy of exercise for treating overweight in children and adolescents: a systematic review.
Atlantis, E, Barnes, EH, Singh, MA
International journal of obesity (2005). 2006;30(7):1027-40
-
-
-
Plain language summary
The global number of overweight and obese children/adolescents is increasing at an alarming rate. This systematic review and meta-analysis aimed to assess the impact of exercise for overweight children/adolescents. Fourteen randomised controlled trials (RCTs) were included in the analysis. Overall the reduction in average body weight and central obesity was not significant. However, it was found that exercise did significantly reduce body fat percentage by 0.6% in studies that involved more exercise (more than 3 days a week) for children with an average age of 12. When results were grouped by exercise amount, it was found that higher amounts had greater effect. Additionally, trials with longer intervention length saw greater effects. None of the trials reached the level of exercise recommended for children by UK/US guidelines (at least 60 minutes a day). The author suggested further studies of longer duration in this area are required to clarify exercise amount response.
Abstract
BACKGROUND Overweight prevalence among children/adolescents is increasing, while adult obesity may potentially cause a decline in life expectancy. More exercise is uniformly recommended, although treatment efficacy remains unclear. OBJECTIVE To determine the efficacy of exercise alone for treating overweight in children/adolescents. DESIGN A systematic review and meta-analysis of randomized trials published in English were completed following multiple database searches performed on December 10, 2004. Studies of isolated or adjunctive exercise/physical activity treatment in overweight/obese children or adolescents which reported any overweight outcome were included. Literature searches identified 645 papers which were manually searched, of which 45 were considered for inclusion, of which 13 papers which reported 14 studies were included (N=481 overweight boys and girls, aged approximately 12 years). Two reviewers independently identified relevant papers for potential inclusion and assessed methodological quality. Principal measures of effects included the mean difference (MD) (between treatment and control groups), the weighted MD (WMD), and the standardized MD (SMD). RESULTS Few studies were of robust design. The pooled SMD was -0.4 (-0.7, -0.1, P=0.006) for percent body fat, and -0.2 (-0.6, 0.1, P=0.07) for central obesity outcomes, whereas the pooled WMD was -2.7 kg (-6.1 kg, 0.8 kg, P=0.07) for body weight, all of which favored exercise. Pooled effects on body weight were significant and larger for studies of higher doses, whereas nonsignificant and smaller effects were seen for studies of lower doses of exercise (155-180 min/weeks vs 120-150 min/weeks). CONCLUSIONS Based on the small number of short-term randomized trials currently available, an aerobic exercise prescription of 155-180 min/weeks at moderate-to-high intensity is effective for reducing body fat in overweight children/adolescents, but effects on body weight and central obesity are inconclusive. Recommendations for future study designs are discussed.