Markers of Renal Function are Unchanged in Obese Older Adults Consuming a Higher Protein, Hypocaloric Diet for 6 Months

Higher intakes of dietary protein (i.e., exceeding the RDA of 0.8 g/kg body weight/day) are being widely advocated for older adults with the intent of mitigating age‐related loss of muscle mass and strength. However, these recommendations are accompanied by concerns about the potential impact on renal function, especially because kidney function declines with age in many individuals. Yet, there is a lack of evidence on the topic, especially in older adults, leading to ambiguity in the clinical setting about the pros and cons of higher protein diets for high‐risk elders whose function is threatened by sarcopenia or sarcopenic obesity. We analyzed blood indicators of renal function collected in our recent trial of higher protein, hypocaloric (500 kcal deficit) diets for obese (mean BMI= 37.7±6.5 kg/m 2 ), functionally frail (by Short Physical Performance Battery) older (mean age = 68.4±5.3 yr) adults (n=40) with age‐normal renal status (estimated glomerular filtration rate [eGFR] ≥ 45 mL/min/1.73m 2 ) to examine the protein effect during a period of challenge to muscle mass (negative energy balance). Control participants were prescribed 0.8 g protein/kg body weight (bw) and Protein participants 1.2 g protein/kg bw distributed as 30+ grams of lean, high‐quality protein three times a day. The Protein group significantly increased dietary protein intake (3‐day diet record) to 1.12 g/kg/bw, while the Control group maintained a protein intake of 0.90 g/kg/bw; both groups had significantly ( P <0.0001) decreased their bw at 6 months (Protein = −7.7±6.0%, Control = −5.7±5.4%). Blood indicators of renal function (eGFR and blood urea nitrogen [BUN]) were assessed at baseline and 6 months. At 6 months, both GFR (Control = 79.7±15.5 and Protein = 77.1±16.6 mL/min/1.73m 2 , P =0.17) and BUN (Control = 17.1±4.8 and Protein = 18.8±5.1 mg/dL, P =0.56) remained unchanged. While additional studies with subject larger numbers are needed, our finding that renal function was not impaired by the higher protein weight loss intervention has important implications for treatment of sarcopenic obesity and aligns with recent recommendations that older adults consume generous amounts of protein at each meal. Support or Funding Information This study was funding by the Beef Checkoff Program and received additional support from the National Institutes of Health (5T32 AG000029; 1P30 AG028716) and the VA Advanced Fellowship Program, GRECC.