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

Overview

The present protocol is mainly involved in the understanding of the local interaction between the released products by fat tissue and hormones production of bone tissue. These complex interactions between adipocyte and osteocyte activities could explain the mechanisms of the body responses to the strategies of weight loss that include diet and/or physical activity program, as well as the side effects encountered by these interventions. Adolescence is a period of development characterized by many metabolic and somatic changes that may influence weight. Weights bearing physical activities are a key factor allowing body composition changes (i.e. fat and bone tissue). The difficulties of managing weight and the onset of overweight and obesity during this very important growth spurt lead to various hormonal dysregulation. The specific mechanisms of the evolution and interactions between these two parameters (fat and bone tissue) are not yet elucidated; therefore our aim is to analyze the possible connections between fat tissue and the quality of the skeleton in order to reduce related risks of the consequence of weight loss in obese individuals.

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.