ADIposity and Bone Metabolism: Effects of eXercise-induced Weight Loss in Obese Adolescents

The complex consequences of childhood obesity represent major concerns in most developed countries, largely contributing to metabolic complications with costly repercussions for the burden of disease. The burden is exemplified by high prevalence rates of overweight or obesity. The ADIBOX protocol was designed to provide a better understanding of the bone-adipocyte cross-talk in adolescents with obesity and the effects of physical activity-induced weight loss on this cross-talk. Obesity effectively leads to hormonal alterations favoring the accumulation of fat mass and loss of bone mass. Advancing the knowledge of the complex interactions between adipocyte and osteocyte activities may contribute to the mechanistic understanding of the body's responses to weight loss during adolescence and prevent cardiovascular risk. Indeed, the adipose-bone tissue cross-talk has been recently linked with cardiovascular diseases. Similarly as adipose tissue, released-products from bone tissue may act directly or indirectly on cardiovascular risk and diseases. The ADIBOX study, a 40 weeks longitudinal study (LS) with repeated measures on four occasions (baseline and every fourteen weeks), will allow us to understand the effects of physical activity-induced weight loss on this cross-talk in obese adolescents. Data will be analyzed using Stata (StataCorp, College Station, USA) and IBM Statistics SPSS version 22 (IBM Corp, 2013, Chicago, IL, USA) and significance will be accepted at a two-sided alpha level of p\<0.05. After testing for normal distribution (Shapiro-Wilk test), data will be treated either by parametric or non-parametric analyses according to statistical assumptions. Student t tests or Mann-Whitney U test will be performed to compare adipose tissue (total, subcutaneous, visceral) variation reported to bone mass variation at lumbar spine between groups at baseline. Pearson (or Spearman when appropriate) correlation coefficient will be used and compared with Fisher test (command corcor Stata) to measure the link between exercise-inducing weight loss on adipose tissue and bone mass variations. Longitudinal data will be treated using a mixed model analyses in order to treat fixed effects group, time and group x time interaction taking into account between and within participant variability.