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Effects of exercise on body composition, aerobic fitness, energy balance and cardiovascular disease risk in overweight Singaporean boys
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Type
Thesis
Author
Lin, Violette Fu Po
Supervisor
Stensel, David
Chia, Michael
Abstract
Introduction: The incidence of childhood obesity in Singapore increased from 5.4% to 15.1% between 1980 and 1991. In response to this, the Ministry of Education initiated the Trim and Fit (TAF) programme in 1992. This study examined the hypothesis that a one-year TAF programme would beneficially influence body composition, aerobic fitness, energy balance and heart disease risk. Besides, the named variables were compared between a group of overweight and normal-weight boys which established the necessity of curbing juvenile obesity as overweight children have greater health risk, especially in cardiovascular diseases, than normal-weight children.
Methodology: Forty-five experimental group (EXP) and 24 control group (CON) boys were recruited from one Singapore secondary school based on age and sex specific weight for height criteria: EXP 2120%, CON 1120%. Their age and height did not differ (age = 13.7±0.6 vs 13.4±0.6 y, height = 1.64±0.08 vs 1.62±0.05 m; mean ± standard deviation values for EXP and CON respectively), but the EXP was significantly heavier than the CON (weight = 73.1±11.7 vs 57.8±5.7 kg). A non-overweight control group was established to assess the influence of maturation in the pubescent EXP boys. This is because it was not possible to obtain a randomly selected control group of overweight boys due to their compulsory commitment to the TAF programme. Exercise intensity on the TAF programme was assessed using heart rate monitors. Peak oxygen uptake (V O2peak) was assessed using a modified Bake treadmill-walking test. Blood lactate concentration was determined at submaximal stages of this test using an Accusport lactate analyser. Percentage body fat (%BF), fat mass (FM) and fat free mass (FFM) were determined using dual energy X-ray absorptiometry. Systolic (SBP) and diastolic @BP) blood pressures were assessed via sphygmomanometry. Serum triglyceride, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), apoprotein AI (ApoAI), apoprotein B (ApoB), lipoprotein(a), glucose and insulin, and plasma fibrinogen concentrations were determined from fasting venous blood samples. Resting metabolic rate (RMR) was measured via indirect calorimetry. All variables were measured at 0,6 and 12 months. Statistical analysis was performed using SPSS version 9.0 for Windows. Significance was set at p<0.05.
Results: At baseline the EXP had greater %BF (37.6±6.1 vs 28.9±5.8), FM (26.09±6.65 vs 15.77±3.69 kg), and FFM (42.97±7.50 vs 38.75±4.86 kg) than the CON. VO2peak (2.52±0.33 vs 2.29±0.22 Llmin) and RMR (7085±616 vs 6462±608 kJ1d) did not differ between groups after adjustment for FFM using analysis of covariance. Serum insulin (19.46±9.82 vs 12.7024.35 mUIL), plasma fibrinogen (3.8950.63 vs 3.38±0.69 G) and SBP (112±11 vs 107±9 mni Hg) were higher in the EXF' than the CON but other blood metabolites and DBP did not differ between goups. A total of 123 TAF sessions were held during the year. The average duration of a session was 33 minutes and the average intensity was 142 beatimin. Attendance on the programme was poor (52%, range: 13%-85%). No significant interactions (two-way analysis of variance) were obtained between the groups for any of the variables examined over the year. However, EXP boys with a better attendance on the programme tended to experience l) a decrease in a submaximal blood lactate concentration at a low exercise intensity and an increase in V 02peak; 2) a smaller increase in FM and weight, and a greater decrease in %BF; and 3) an increase in ApoAVApoB and decreases in TC/HDL-C, SBP and DBP.
Conclusion: There were signs that the EXP were at elevated heart disease risk compared to the CON. The EXF' were having higher risk of diabetes, thrombotic risk and higher blood pressure level which might be due to their overweight or obese status. The TAF programme had limited impact on the variables examined. The most likely explanation for this was poor adherence and low exercise intensity. There were some signs that greater adherence would be of benefit.
Methodology: Forty-five experimental group (EXP) and 24 control group (CON) boys were recruited from one Singapore secondary school based on age and sex specific weight for height criteria: EXP 2120%, CON 1120%. Their age and height did not differ (age = 13.7±0.6 vs 13.4±0.6 y, height = 1.64±0.08 vs 1.62±0.05 m; mean ± standard deviation values for EXP and CON respectively), but the EXP was significantly heavier than the CON (weight = 73.1±11.7 vs 57.8±5.7 kg). A non-overweight control group was established to assess the influence of maturation in the pubescent EXP boys. This is because it was not possible to obtain a randomly selected control group of overweight boys due to their compulsory commitment to the TAF programme. Exercise intensity on the TAF programme was assessed using heart rate monitors. Peak oxygen uptake (V O2peak) was assessed using a modified Bake treadmill-walking test. Blood lactate concentration was determined at submaximal stages of this test using an Accusport lactate analyser. Percentage body fat (%BF), fat mass (FM) and fat free mass (FFM) were determined using dual energy X-ray absorptiometry. Systolic (SBP) and diastolic @BP) blood pressures were assessed via sphygmomanometry. Serum triglyceride, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), apoprotein AI (ApoAI), apoprotein B (ApoB), lipoprotein(a), glucose and insulin, and plasma fibrinogen concentrations were determined from fasting venous blood samples. Resting metabolic rate (RMR) was measured via indirect calorimetry. All variables were measured at 0,6 and 12 months. Statistical analysis was performed using SPSS version 9.0 for Windows. Significance was set at p<0.05.
Results: At baseline the EXP had greater %BF (37.6±6.1 vs 28.9±5.8), FM (26.09±6.65 vs 15.77±3.69 kg), and FFM (42.97±7.50 vs 38.75±4.86 kg) than the CON. VO2peak (2.52±0.33 vs 2.29±0.22 Llmin) and RMR (7085±616 vs 6462±608 kJ1d) did not differ between groups after adjustment for FFM using analysis of covariance. Serum insulin (19.46±9.82 vs 12.7024.35 mUIL), plasma fibrinogen (3.8950.63 vs 3.38±0.69 G) and SBP (112±11 vs 107±9 mni Hg) were higher in the EXF' than the CON but other blood metabolites and DBP did not differ between goups. A total of 123 TAF sessions were held during the year. The average duration of a session was 33 minutes and the average intensity was 142 beatimin. Attendance on the programme was poor (52%, range: 13%-85%). No significant interactions (two-way analysis of variance) were obtained between the groups for any of the variables examined over the year. However, EXP boys with a better attendance on the programme tended to experience l) a decrease in a submaximal blood lactate concentration at a low exercise intensity and an increase in V 02peak; 2) a smaller increase in FM and weight, and a greater decrease in %BF; and 3) an increase in ApoAVApoB and decreases in TC/HDL-C, SBP and DBP.
Conclusion: There were signs that the EXP were at elevated heart disease risk compared to the CON. The EXF' were having higher risk of diabetes, thrombotic risk and higher blood pressure level which might be due to their overweight or obese status. The TAF programme had limited impact on the variables examined. The most likely explanation for this was poor adherence and low exercise intensity. There were some signs that greater adherence would be of benefit.
Date Issued
2001
Call Number
GV481 Lin
Date Submitted
2001