Cardiorespiratory fitness, insulin sensitivity, and perceptions of obesity treatment in obese children and adolescents

University dissertation from Stockholm : Karolinska Institutet, Department of Neurobiology, Care Sciences and Society

Abstract: Background and Aims: The childhood obesity epidemic is accelerating throughout the world and is associated with long-term medical and psychosocial consequences. To gain knowledge for clinical practice and further research, the overall aims of this thesis were to explore and describe obese children s and adolescents physical fitness, participation in organized physical activity, and insulin sensitivity (SI). A further aim was to describe obese adolescents perceptions of obesity treatment. Material and Methods: Obese children and adolescents registered at a childhood obesity clinic, and age-matched reference groups participated. The following assessments were performed: a submaximal bicycle ergometry test, an interview regarding participation in organized physical activity, the frequently sampled intravenous glucose tolerance test (FSIVGTT), a dual-energy X-ray absorptiometry (DEXA), the six-minute walk test (6MWT), and a semi-structured interview regarding perceptions of obesity treatment. Results: The obese children and adolescents had lower estimated relative maximal oxygen uptake (VO2max), and participated less in organized physical activity, than the reference group did. Non-participation increased with age. Among the 14-16-year-olds 19% of the obese boys and 12% of the obese girls did not participate at all in physical education classes, compared to 2% in the reference group. Relative VO2max was a stronger predictor of SI than body composition was. The six-minute walk distance (6MWD) performed by obese children averaged 86% of the distance normal-weight children walked. In test-retest of the 6MWT, the measurement error (Sw) was 24 m, coefficient of variation (CV) 4.3%, and the intra-class correlation (ICC1.1) 0.84. The correlation between 6MWD and estimated VO2max was low (r = 0.34). For the interview study, a phenomenographic research approach was chosen. The obese adolescents showed six qualitatively different ways of perceiving and responding to obesity treatment: a) personal empowerment, b) despair and disappointment, c) safety and relief, d) ambivalence and uncertainty, e) acceptance and realization, and f) shame and guilt. The categories had two contrasting internal structures regarding main focus and treatment objective: focus on the individual and focus on weight. Conclusions: Obese adolescents, especially boys, were at risk of physical inactivity. This necessitates changes in the design of physical education programs in which obese adolescents participate. Relative VO2max was a stronger predictor of SI than body composition was. Efforts to improve SI and prevent type 2 diabetes (T2DM) should include physical activity targeting cardiorespiratory fitness also in this population. The 6MWT showed good reproducibility and known group validity in obese children and adolescents, and can be recommended for use in clinical practice in the population studied. To evaluate individual outcomes after intervention, the 6MWD needs to have changed by > 68 m to be statistically significant. The correlation between 6MWD and estimated VO2max was low, hence the 6MWT cannot replace a bicycle ergometry test. Adolescents at a pediatric obesity clinic varied broadly in how they perceived and understood the treatment program, how they related to the staff, and how they responded and reacted in the treatment process. Knowledge of such perceptions has relevance for health-care professionals seeking to accomplish successful treatment and interventions.

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