A 5-month weight-reduction programme has a positive effect on body composition, aerobic fitness, and habitual physical activity of severely obese girls: A pilot evaluation study

Abstract

In this pilot study, we wished to determine whether a 5-month multidisciplinary programme of a combined dietary-nutritional education-exercise intervention would have favourable effects on the health status of 18 obese adolescent girls. Before and after the clinical intervention, body composition and habitual physical activity were assessed by bioelectrical impedance and accelerometry, respectively. Aerobic fitness and substrate utilization were determined by gas exchange using an incremental field test that mimics habitual conditions. Despite a significantly (P < 0.001) greater loss of fat mass (-8.7 +/- 4.1 kg) compared with fat-free mass (-2.8 +/- 2.2 kg), energy expenditure at rest decreased by 9% following the intervention. Maximal oxygen consumption [Vdot]O2max related to fat-free mass increased by 7% (P < 0.05), whereas substrate utilization during exercise did not change following the intervention. Moderate and intense physical activity increased by 15% (+20 min . day(-1); P < 0.05) and 45% (+25 min . day(-1); P < 0.01), respectively. A significant relationship was observed between change in habitual physical activity and change in .[Vdot]O2max fat-free mass (r = 0.56, P = 0.01). The present multidisciplinary programme enhanced the loss of fat mass relative to fat-free mass but not sufficiently so to prevent a decline in metabolic rate during rest. Our results suggest a coupling in the improvement of aerobic fitness and habitual physical activity in obese adolescent girls, and hence an improvement in behaviour in relation to physical activity.

Severely obese adolescent girls rely earlier on carbohydrates during walking than normal-weight matched girls

“…In the present study, the intensity at which maximal lipid oxidation and the corresponding crossover point occur in obese girls were identified during an incremental field test (Aguer et al, 2010). This test is characterised by greater ecological validity than laboratory tests performed on a bicycle ergometer or a treadmill because the activity patterns and muscle mass recruited are more representative of daily activities.…”

“…The within-participant coefficient of variation for the repeat _ V O 2 ranged from 2.5% to 4.7% during the last minute of each stage (15-s samples). Estimated maximal oxygen consumption (E _ V O 2max ) was calculated from the HR-_ V O 2 relationship up to the theoretical maximal HR (HR max = 220-age) (Aguer et al, 2010;Breithaupt, Adamo, & Colley, 2012;Lazzer et al, 2007Lazzer et al, , 2010Lazzer, Molin, Stramare, Facchini, & Francescato, 2008). The average R 2 value relative to the HR-_ V O 2 regression line was 0.978 ± 0.013 in obese girls and 0.984 ± 0.014 in normal-weight girls.…”

“…Additionally, heart rate (HR) was measured using a Polar HR monitor (Vantage NV, Kempele, Finland). After becoming familiar with testing equipment, participants followed a progressive submaximal field test (Aguer et al, 2010). Adolescents walked 4 min at 2 km · h −1 , then the speed was increased by 1 km · h −1 every 4 min (2 to 6 km · h −1 , walking) and then by 2 km · h −1 every 4 min (7 to 11 km · h −1 , running).…”

“…The procedures of calibration have been described elsewhere (Aguer et al, 2010). Additionally, heart rate (HR) was measured using a Polar HR monitor (Vantage NV, Kempele, Finland).…”

“…Carbohydrate (CHO) and lipid oxidation rates during the submaximal field test (Aguer et al, 2010) were calculated from the gas exchange measurements according to the non-protein respiratory quotient technique (Peronnet & Massicotte, 1991). After smoothing the curves, two parameters representative of the balance between fat and CHO utilisation induced by increasing exercise intensity were calculated (Perez-Martin et al, 2001): (a) the crossover point of substrate utilisation (CP), defined as the intensity at which energy derived from CHO becomes predominant over energy from lipids, (b) the maximal lipid oxidation rate (Lipox max ), defined as the point where the rise in lipid oxidation induced by increasing intensity reaches a maximum, which will then be followed by a decrease since CHO becomes the predominant fuel.…”