Optimizing Adaptive Intensive Behavioral Therapy for Obesity During the Transition to Older Adulthood

This Sequential Multiple Assignment Randomized Trial (SMART) seeks to identify the optimal initial dietary strategy (high vs. standard protein diets) and as-needed augmentation strategy (protein supplementation vs. supervised resistance exercise training) for behavioral weight loss in adults aged 50-75. Augmentation strategies will only be used for participants who do not achieve at least 3% weight loss and/or those who lose more than 1.5 kg of fat free mass (i.e., Non-Responders) after 8 weeks of group-based behavioral obesity treatment. Protein supplements and supervised resistance exercise training will be provided at no-cost to participants for weeks 9-16 of the study. Responders (i.e., achieving at least 3% weight loss and less than 1.5 kg loss of fat free mass) will continue with their initial high protein or standard protein diet assignment for the remainder of the trial. This SMART will enroll 250 adults aged 50-75 years with a BMI of at least 30 kg/m2. All participants will receive 1 year of behavioral obesity treatment including 16 weeks of weekly group-based treatment (active weight loss phase) followed by 36 weeks of monthly group sessions to promote continued engagement in dietary and exercise behaviors and long-term weight loss maintenance. The behavioral intervention will be delivered via Zoom. Data collection will occur at the University of Alabama at Birmingham and 5 study visits will be scheduled including: screening (to determine eligibility), prior to starting the weight loss intervention (baseline), and at weeks 8, 16, and 52.

Inclusion criteria

• Male or female sex
• all racial and ethnic groups
• BMI: 30-50 kg/m2
• age 50-75 years
• postmenopausal status for ≥1 y if female sex

Exclusion criteria

• <3 months stable use of other medications affecting body weight or appetite
• >450 pounds (due to weight limitations of the DXA)
• indication or previous diagnosis of sarcopenia
• existing kidney disease
• current binge eating disorder, anorexia, or bulimia
• untreated hyper- or hypothyroidism, cancer (except basal cell), gastrointestinal disorders affecting food intake or nutrient absorption; any other medical condition, as determined by the study physician, precluding a HP diet and/or daily exercise