Changes in lean mass and bone parameters in obese children participating in a family‐centered lifestyle intervention: results from a 1‐year RCT

During childhood, both fat and lean mass (LM) influence bone development. Lifestyle behaviors, notably diet and physical activity (PA), influence adiposity and bone development though it is unknown if an intervention that focuses on dietary and PA guidelines favorably changes LM and bone parameters. Furthermore, it is not known if increasing milk and milk products and specifically weight‐bearing PA in obese children have any additive benefits on bone. Therefore, the aim of this study is to assess the changes in LM and bone parameters assessed by dual‐energy X‐ray absorptiometry (DXA) in overweight and obese children participating in a 1‐year family‐centered lifestyle intervention. Children (6–8 y) classified as overweight or obese according to WHO body mass index‐for‐age z‐scores (BAZ) were recruited from Montréal (QC, Canada). Children were randomized to 1 of 3 groups: Standard (StnTx; 2 servings milk and alternatives/d, meet PA guidelines), Modified (ModTx; 4 servings milk and alternatives/d; emphasis on daily weight‐bearing plus meet PA guidelines) or Control (Ctrl; no intervention). Whole body (WB) DXA (Hologic Discovery APEX software version 13.3) scans were performed at baseline and 12‐months for analysis of LM, LM index (LMI), fat mass (FM) and WB bone parameters (bone mineral density (BMD), BMD z‐scores, bone mineral content (BMC)). Parents completed a 3‐day food diary to assess dietary intake; total screen hours/week was surveyed. Statistics included Pearson's correlations and repeated‐measures mixed model ANOVA with post‐hoc adjustments to test for differences and changes (Δ) among the groups for body composition and bone variables from baseline to 12‐months. Models accounted for parental education and family income. Seventy‐eight children were recruited; 73 completed the 12‐month visit. At baseline, the majority were Caucasian (81%) and classified as obese (92%, mean BAZ: 3.3±1.2) with mean WB BMD z‐scores of 2.7±1.2, WB LM of 25.8±4.1 kg and FM of 16.3±4.6 kg. Groups did not differ at baseline for body composition or bone variables. Baseline LM was strongly associated with FM (r=0.64; p<0.001). Milk and alternative intake (n=50) did not associate with LM or FM, however total screen time (n=72; mean: 6.8±3.2 h/week) was positively associated with LM (r=0.25, p=0.032). By 12‐months, all groups significantly increased LM (p<0.001) however the ΔLM was significantly less in ModTx compared to StnTx (p=0.003) and Ctrl (p<0.001). Ctrl had a greater ΔFM at 12‐months compared to ModTx (p=0.002). WB BMC increased in all groups (p<0.001), but was not significantly different among groups. Finally, WB BMD z‐scores were significantly lower at 12‐months compared to baseline in Ctrl (p=0.012), but not in the intervention groups. Overweight and obese children who participated in a 1‐year family‐centered lifestyle intervention that focused on dietary and PA guidelines resulted in reduced adiposity while also supporting bone health, specifically WB BMD z‐scores. Support or Funding Information Trial registration: ClinicalTrials.gov: NCT01290016; Supported by a contribution from the Dairy Research Cluster Initiative (Dairy Farmers of Canada, Agriculture and Agri‐Food Canada, the Canadian Dairy Network and the Canadian Dairy Commission). H.W. is supported by Canada Foundation for Innovation, and Canada Research Chairs Program. T.C. is supported by Canadian Institutes for Health Research Doctoral Research Award