Abstract
BACKGROUND: Weight loss improves cardiometabolic and functional outcomes, but may worsen sarcopenia. Protein intake during energy restriction may preserve lean body mass (LBM). The amount, timing and source of protein may be important. No formal protein guidelines exist in older adults attempting weight loss. We evaluated the types of protein used in weight-loss interventions. METHODS: With a reference librarian, we conducted a PubMed search using the terms weight loss intervention, diet intervention, energy restriction, hypocaloric diets, protein, protein supplementation, obese, and older adults for the years ranging from 2003–2018. Systematic reviews on this topic were also reviewed. Our inclusion criteria consisted of randomized controlled trials of weight loss studies with subjects aged >60 and a body mass index (BMI) >30 kg/m2. Studies entailed a comprehensive energy-restricted diet with protein from food or supplements, with or without an exercise component. RESULTS: Out of 158 citations, 13 trials met criteria. Sample size ranged from 11–148, age and BMI ranged from 65.2–70.3years and 31-40kg/m2. Interventions lasted 4–52 weeks and all included protein above the current Recommended Dietary Allowance (RDA) of 0.8g/kg/day. LBM decreased when protein intake remained at the RDA. Increased protein intake was associated with improved function. Protein intake (>1.0-1.2g/kg or 20–30% of total calories) spread evenly throughout the day, with 20–30g at each meal, preserved LBM and function. Whey protein also exerted beneficial effects on muscle but somewhat inconclusive. CONCLUSIONS: Current RDA may be inadequate to preserve LBM during weight loss in older adults.