MY LIFE Study - McGill Youth Lifestyle Intervention With Food and Exercise Study

Rationale: Childhood obesity is an increasingly major health care problem in Canada. Not only are approximately 30% of Canadian children overweight/obese, but they are developing significant sequelae including insulin resistance, hyperinsulinemia, hyperlipidemia, hypertension, and diabetes mellitus. Additionally obese children have lower bone mass, lower 25(OH)D concentrations and fracture more frequently. Canadian children on average do not meet the recommended intakes for vegetables and fruit and only half of those < 8 years old meet the recommended intakes for milk. Obese children are more likely to be inactive and spend more screen-time during their free time. There is promising childhood evidence that diets with 3 to 4 servings of milk support healthier body composition (lean mass and height) and improved insulin sensitivity in the short term and bone mass in the longer term. Family based interventions are effective in weight reduction in children. To date, a combined assessment of the benefits of improved intakes of milk plus active lifestyles in obese children on body composition, bone and blood biochemistry in a family intervention is lacking.

Objectives and Hypotheses:

1. To determine if a 1-year lifestyle intervention with planning sessions designed to improve diet and activity within the context of the family environment will reduce adiposity and elevate lean mass while supporting bone mass in obese children compared to a control group and if augmented intake of milk to 4 daily servings will result in superior changes. The primary outcome will be change in body mass index (BMI) Z-score along with waist circumference for assessment of adiposity; selected for ease of use in larger studies or clinics where body composition assessment is not feasible.

Hypothesis: the lifestyle intervention will yield modest changes to adiposity and lean mass accompanied by no reductions in bone mass, but that the augmented milk intervention will yield superior reductions in adiposity and elevations in lean and bone mass and height growth. It is hypothesized that bone mass will be low and that maintenance of bone mass in the standard intervention will thereby be judged as inadequate. 2. To explain the hypothesized benefits of these interventions on lean, adipose and bone masses by measuring indicators of glucose metabolism, satiety and related gut hormones along with novel biomarkers of skeletal metabolism including osteocalcin, adiponectin and vitamin D.

Hypothesis: high milk intake will associate with lower glucose, insulin, ghrelin and 1,25(OH)2D accompanied by higher 25(OH)D, osteocalcin, peptide YY and glucagon-like peptide 1. 3. Test if the intervention with higher milk servings is linked to changes in child eating behavior and satiety using the Child Eating Behavior Questionnaire to reflect eating in the child's normal environment.