Effects of Dietary Protein Intake and Resistance Training on Retention of Fat Free Mass During Weight Loss in Adults Over 50 With Obesity

This is a sequential multiple assignment randomized trial (SMART) experimental design. Study testing took place at the University of Alabama at Birmingham (UAB) Wellness, Health, and Research Facility (WHARF) on the Lakeshore Foundation Campus in Birmingham, Alabama.

Overview of the State of Slim Weight Management Program All study participants will be enrolled in the SOS weight management program. SOS is a 16-week group-based behavioral weight loss program (up to 20 per group). The usual SOS diet plan is HP, low in fat and emphasizes non-starchy vegetable and whole-grain carbohydrates. The diet is plan is structured into 3 distinct phases with phase-specific food choices from which participants can chose to eat in defined portions rather than counting calories. Phase 1 is 2 weeks long, Phase 2 is 6 weeks, and Phase 3 is 8 weeks, and additional foods are added to the food choices as participants complete each phase. The SOS diet plan utilizes 5 'Diet Rules' through all 3 phases of the diet to encourage weight loss: (i) Eat 6 times per day; (ii) Have breakfast within 1 h of waking; (iii) Don't count calories, measure portions; (iv) Have the right carbohydrate and protein mix at every meal (1 carbohydrate and 1 protein at every meal, vegetables as only carbohydrate source at 3 meals); and (v) Eat a healthy fat twice a day. SOS also includes a strong exercise component with a prescription to exercise on 6 days per week and to progressively increase exercise duration from 10 min/d to 70 min/d. Participants in the commercial SOS program are encouraged to reach the goal of 420 weekly minutes of exercise through any combination of aerobic, strength, and alternative (e.g., yoga, Pilates, flexibility, balance) exercise training. Weekly group sessions cover topics related to weight management and behavior change such as building motivation, managing stress, practicing new habits, and finding social support.

Research Modifications to State of Slim For this study, participants were randomly assigned to the HP group follow the unmodified SOS diet plan in the published book whereas participants assigned to the RT group follow a modified version (described below) with 3 days per week of self-direct RT that will contribute ~135 minutes per week (45 min/session) to the 420 minutes per week exercise goal (RT group). The 1st and 2nd stage SMART interventions for each group are described below. All participants had access to the online SOS community during the entire study where they could interact/connect with other participants from their group and also have access to the coach who will be available to provide information and answer questions. The SOS community is a private Facebook group that is only open to participants in that specific SOS group.

First-Stage Interventions- High Protein Diet Counseling Participants in this group followed the usual SOS diet. The estimated macronutrient distribution is 40% protein (or ~1.8 g/kg body weight/d), 32% carbohydrate, and 28% fat. Prior to the start of the intervention, participants completed a virtual orientation session with a personal trainer via zoom who demonstrated a sequence of balance and flexibility exercises (single limb stance, heel-to-toe walk, standing side leg raise, standing back leg raise). Participants were instructed to engage in this sequence and any other balance and flexibility exercises (i.e., yoga, Pilates etc.) for approximately 45 minutes per day that contributed to the overall 420 minutes per week and to avoid any RT for the duration of the study.

First-Stage Interventions- Standard Protein Diet Counseling plus RT In order to control for the overall degree of dietary energy restriction, participants assigned to RT were prescribed a modified SOS diet that is lower in protein (20% of energy or ~0.9 g/kg body weight/d), proportionally higher in carbohydrate (53% of energy), and approximately equivalent in fat (26% of energy), but using the same overall food sources. Protein portions listed in the SOS Diet Rules were decreased to 2-3 ounces per meal and requiring non-vegetable carbohydrate foods at all 6 meals to achieve targeted differences in macronutrient composition between the diet plans. Prior to initiating the SOS program, participants assigned to RT were given resistance bands (either Premium Versa Tube, Power Systems, Knoxville TN, 37909, USA or Black Mountain Resistance Bands Set, Black Mountain Products, Inc. Spring Grove, IL 60081, USA) to use for the duration of the study. They also completed a virtual RT orientation session with a personal trainer via zoom to demonstrate proper technique for exercises and discuss the plan for RT progression (e.g., increase number of sets). They were instructed to engage in self-directed RT using the provided resistance bands and work up to three sets of 8-12 repetitions of eight exercises (squat, heel raise, overhead press, chest press, row, arm curl, triceps push-down, and abdominal flexion). Participants were instructed to begin with one set of each exercise and to add additional sets once s/he was able to achieve 12 repetitions of all exercises.