Utilizing Protein During Weight Loss to Impact Physical Function and Bone

This study is an ancillary study to the Utilizing Protein During Weight Loss to Impact Physical Function (UPLIFT) trial (NCT03074643) to evaluate the effects of diet composition (i.e., amount of protein and carbohydrate) during a 6-month weight loss intervention and 12-months of follow-up on bone phenotypes in obese older adults. Participants will receive either a protein or carbohydrate supplement along with a behavioral weight loss intervention.

The ancillary study to the UPLIFT trial (NCT03074643) will use a 3-group design in 225 obese (body mass index \[BMI\] 30-45 kg/m2 or 27-\<30 kg/m2 with an obesity-related risk factor), older (65-85 years) men and women at risk for disability (Short Physical Performance Battery, SPPB ≤10) who will undergo a 6-month weight loss intervention followed by a 12-month follow-up phase to test the overall hypothesis that a higher protein (1.2 g/kg body weight/day) / lower carbohydrate (CHO) diet during a 6-month weight loss intervention improves bone phenotypes compared with an isocaloric lower protein (the current Recommended Dietary Allowance (RDA), 0.8 g/kg body wt/d) / higher CHO diet, and whether continuing a higher protein / lower CHO diet for 12-months following weight loss will result in better maintenance of bone. All participants will undergo a 6-month weight loss intervention involving caloric restriction and supervised exercise followed by 12 months of follow-up with randomization to one of three groups (n=75/group): 1) Lower protein / higher CHO diet for the 6-month weight loss phase only (RecProt); 2) Higher protein / lower CHO diet for the 6-month weight loss phase only (6-mo HiProt); or 3) Higher protein / lower CHO diet for the 6-month weight loss and 12-month follow-up phases (18-mo HiProt). Vertebral and femoral volumetric bone mineral density and cortical thickness (Primary Aim) and bone marrow adipose tissue (Secondary Aim 1) will be assessed with computed tomography at baseline, 6-, and 18-months. Bone strength and fracture risk (Secondary Aim 2) will be assessed by finite element modeling at baseline, 6-, and 18-months.