Costa, S;
Christie, D;
Hudson, LD;
Kinra, S;
Mathiot, A;
Viner, RM;
HELP Trial Study Group;
(2015)
Objectively measured physical activity and sedentary behaviour in obese adolescents, and their relationship with fatness and metabolic outcomes.
Presented at: 14th Meeting of the International Society for Behavioral Nutrition and Physical Activity, Edinburgh (UK).
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Abstract
PURPOSE: To describe the physical activity (PA) and sedentary behaviour (SB) levels of obese adolescents (12-19 year-olds), and investigate the association of SB and moderate-to-vigorous PA (MVPA) with fatness and metabolic outcomes. METHODS: Baseline measurements were obtained from 102 obese (body mass index (BMI)>95th centile UK1990 reference) adolescents participating in a multicomponent obesity treatment trial- the Healthy Eating and Lifestyle Programme. PA/SB were measured with ActiGraph accelerometers (15-second epochs), time spent in SB, PA and MVPA was derived using Evenson et al’s (2007) cut-points, and participants were included for analyses if providing ≥3 valid days (≥10hours wear-time). Total, low- and high density lipoprotein cholesterol, triglycerides, insulin and glucose were obtained from fasting blood samples. Height, weight and waist circumference were measured by trained staff, fat mass (FM) and fat-free mass (FFM) were determined from bio-impedance analyses, and BMI and FM Index (FM/height2) were derived. Sex differences were assessed with chi-square or Mann-Whitney U tests, and associations of MVPA and SB with fatness and metabolic outcomes were assessed with univariable and multivariable linear regression. RESULTS: Adolescents spent a median of 4.5 hours/day in PA (including 38.5 min/day MVPA) and 12.7 hours/day in SB, with 86% spending over two thirds of their day in SB. Boys spent more time in MVPA than girls (median: 48.6min versus 35.9min; p=0.004), and were more likely to meet guidelines of ≥60 min/day in MVPA (24.3% versus 9.2%; p=0.04). Univariable regressions showed significant associations of MVPA with FM Index (B= -0.05), FM (B= -0.11) and FFM (B=0.14), and SB with Insulin (B=-0.02; all p<0.05). After including MVPA and SB in the same model and adjusting for age, sex, and wear-time, only MVPA remained significantly associated with FM Index (B= -0.05; p=0.04) and FFM (B= 0.13; p=0.008). CONCLUSIONS: Most adolescents did not meet current UK PA guidelines, and spent a worryingly high proportion of their day in SB. Although causality cannot be inferred, results highlight theimportance of promoting MVPA to improve the body composition profiles of obese adolescents.
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