Influence of protein intake during weight loss on inflammatory response of obese, frail older adults

Both aging and obesity increase levels of pro-inflammatory factors, contributing to muscle loss and a negative cycle of functional decline. While obesity reduction improves inflammation, the concomitant loss of muscle mass is a serious concern in older adults. Indications that increased protein intake preserves lean muscle during weight loss are promising, but studies of protein effects on inflammation during weight loss are few and their findings equivocal. Thus, we examined the influence of increased protein intake on inflammatory markers in a 6-month, randomized, controlled weight reduction study of obese (BMI ≥30 kg/m2), older (≥60 years) adults with physical frailty (Short Physical Performance Battery [SPPB] score 4–10), who were randomized to either a Control weight loss diet (0.8 g protein/kg/day; C-WL; n=14) or a higher protein (animal source, 2/3rds beef) diet (1.2 g protein/kg/day; HP-WL; n=25) in a 1:2 ratio. Reduced kcal intake in both arms and target protein intake in HP-WL were confirmed by 3-day records. Outcomes included function by SPPB and serum levels of 11 biomarkers of inflammatory status. In both arms, weight loss (~8%) was achieved and SPPB score improved, with a superior functional response in HP-WL (P<0.05). Several markers of inflammation improved, but only in the HP-WL group, for whom leptin (P<0.001), CRP (P<0.01), and ICAM-1 (P<0.01) were decreased and adiponectin increased (P<0.01); however, only adiponectin trended (P<0.07) towards a difference by group. Findings from this pilot study show beneficial inflammatory responses to HP-WL in obese, frail older adults; however, confirmation in a larger study is needed.