Utilizing Protein During Weight Loss to Impact Physical Function
Condition: Obesity; Weight Loss; Diet Modification; Aging; Weight Change, Body; Dietary Habits
MeSH terms: Body Weight; Weight Loss; Body Weight Changes
Study type: Interventional

Summary: 
      This study will 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
      physical function, muscle mass, and weight loss maintenance in obese older adults.
      Participants will receive either a protein or carbohydrate supplement along with a behavioral
      weight loss intervention.
    

Detailed description: 
      The study will use a 3-group design in 225 obese (BMI 27-45 kg/m2), older (65-85 years) men
      and women at risk for disability (eSPPB <2.5) 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 wt/d) / lower carbohydrate (CHO) diet during a 6-month weight
      loss intervention improves physical function 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 improved physical function. 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). Physical function (primary aim) will be assessed by the expanded Short Physical
      Performance Battery (primary outcome) and lower extremity muscle strength at baseline, 6-,
      12- and 18-months. Weight loss maintenance and body composition (secondary aim) will be
      assessed by dual-energy X-ray absorptiometry (DXA) and computed tomography (CT) at baseline,
      6- and 18-months. Bone mineral density (DXA) and cardiometabolic risk factors will also be
      measured at baseline, 6- and 18-months.
    

Intervention name(s): Weight loss intervention months 0-6; Exercise intervention months 0-6; Carbohydrate supplement for months 0-6; Protein supplement for months 0-6; Protein supplement for follow-up months 7-18
Intervention type(s): Behavioral; Behavioral; Dietary Supplement; Dietary Supplement; Dietary Supplement
Intervention description(s): All participants will undergo a dietary weight loss intervention designed to elicit behavioral changes leading to decreased caloric intake sufficient to yield a ~10% loss of initial body mass. The weight loss intervention will incorporate nutrition education (via group and individual meetings with the study dietitian), self-monitoring skills, cognitive-behavioral strategies for promoting lifestyle behavior modifications, and planned meals. Behavioral and educational group and individual sessions will be held weekly in a 3:1 ratio (3 group and 1 individual session per month).; All participants will be expected to participate in a supervised, center-based exercise program involving moderate-intensity aerobic exercise (e.g., treadmill walking) 3 days/wk during the 6-month weight loss intervention in accordance with the American Heart Association and the American College of Sports Medicine physical activity recommendations for older adults.; Participants in the lower protein / higher CHO diet group (RecProt) will be provided a carbohydrate supplement (~50 g of carbohydrate and 220 calories) to consume daily during the 6 month weight loss intervention.; Participants in the higher protein / lower CHO diet groups (6-mon HiProt and 18-mon HiProt) will be provided a protein supplement (~50 g of protein and 220 calories) to consume daily during the 6 month weight loss intervention.; Participants in the higher protein / lower CHO diet (18-mon HiProt) will be provided a protein supplement (~50 g of protein and 220 calories) to consume daily during the 12-month follow-up.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: All participants will undergo a 6-month weight loss intervention of 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).
Masking: Triple (Participant, Investigator, Outcomes Assessor)
Primary purpose: Treatment