Is higher protein intake during weight loss interventions in older adults associated with improved outcomes? A secondary data analysis of three randomised controlled trials

Abstract Background Weight loss interventions can exacerbate sarcopenia and sarcopenic obesity in older individuals. Increasing protein intake, alongside resistance training, is suggested to help preserve muscle mass, strength, and function during energy-restricted diets, but the benefits are not consistently supported by all studies in older adults. Objective To investigate the relationship between protein intake and body composition, muscle strength, and function in weight loss programs with energy restriction, with or without increased protein intake (through supplementation or dietary counseling) and combined with resistance training in older adults with overweight or obesity. Methods A secondary data analysis of three randomized controlled trials was conducted, including participants aged ≥ 55 with a BMI ≥ 25 kg/m². Data on protein intake at baseline and follow-up were analyzed. The follow-up period was 10 weeks in one study and 13 weeks in the other two studies.Outcomes included body weight, body fat, appendicular lean soft tissue mass (ALST), handgrip strength (HGS), gait speed, chair stand test (CST), and short physical performance battery (SPPB). Linear mixed models were used to identify associations between protein intake and outcomes. Results A total of 191 older adults (mean age 65.1 years, mean BMI 32.9 kg/m²) were included. Protein intake significantly increased from 0.87 to 1.06 g/kg BW/day (p < 0.001) in participants receiving protein supplementation or dietary advice. Higher protein intake was significantly associated with increased ALST (beta = 1.0, p = 0.047), but no associations were found with body weight, body fat, HGS, gait speed, CST, or SPPB. Conclusions Increasing protein intake during weight loss interventions may help preserve ALST in older adults with overweight or obesity, potentially reducing the risk of sarcopenia. These findings suggest that incorporating protein strategies in weight loss programs is beneficial for muscle health in older adults. Further high-quality studies are needed to determine the optimal protein intake for this population. Trial registration Trial registration in the Dutch Trial Register: MPS: NL2623, https://www.onderzoekmetmensen.nl/en/trial/24688 , registration date 11022011 WelPrex NL4434 https://www.onderzoekmetmensen.nl/en/trial/29590 , registration date 01052014 PROBE NL4357, https://www.onderzoekmetmensen.nl/en/trial/21917 ), registration date 08042014.