BACKGROUND&AIMS: Obesity and sarcopenia are major health concerns, particularly among older populations. Dietary protein may help preserve muscle mass and function, but high-protein diets, especially from animal sources, may also increase adipose mass. We investigated associations of total, animal, and plant protein intake with body composition trajectories, sarcopenia, and sarcopenic obesity. METHODS: We included 4576 participants (mean age 65.1 years, 56 % women) from the population-based Rotterdam Study. Dietary protein was measured using food-frequency questionnaires at baseline (2004-2009). Body composition was measured every 4-5 years using dual X-ray-absorptiometry. Handgrip strength (HGS) was assessed starting 2006 using a hydraulic dynamometer. Sarcopenia was determined based on low appendicular skeletal muscle and HGS; and sarcopenic obesity risk based on measures of lean mass, HGS and body fat. Analyses used linear mixed models and generalized estimate equation models. RESULTS: Higher total protein intake was associated with increased BMI over time (mean difference [95 %-confidence interval (CI)]: 0.86 kg/m2 [0.01,1.71] per 5E% increase), and increased fat-mass index (1.33 [0.67,1.99]), body-fat-percentage (4.54[2.76,6.31]), and both gynoid and android fat percentage. Higher protein intake was also associated with a higher sarcopenic obesity risk (-0.85[-1.5,-0.2]), but with a lower sarcopenia risk (odds ratio: 0.62 [0.43,0.90]). These associations were mainly driven by animal protein. CONCLUSION: Higher protein intake, particularly from animal food sources, is protective against sarcopenia but also linked to a higher obesity risk. A balanced protein intake advice for older persons should be formulated based on individual needs and health status to prevent sarcopenia, obesity, and sarcopenic obesity.

Amsterdam University of Applied Sciences Center of Expertise Urban Vitality Faculty of Sports and Nutrition Amsterdam the Netherlands

Amsterdam University of Applied Sciences Center of Expertise Urban Vitality Faculty of Sports and Nutrition Amsterdam the Netherlands; Department of Nutrition and Dietetics Amsterdam University Medical Centers Amsterdam Public Health Research Institute VU University Amsterdam the Netherlands

Department of Epidemiology Erasmus MC University Medical Center Rotterdam the Netherlands

Department of Epidemiology Erasmus MC University Medical Center Rotterdam the Netherlands; Department of Cardiovascular Medicine The 2nd Xiangya Hospital Central South University Changsha Hunan China; FuRong Laboratory Changsha Hunan China

Department of Epidemiology Erasmus MC University Medical Center Rotterdam the Netherlands; Department of Internal Medicine Erasmus MC University Medical Center Rotterdam the Netherlands

Department of Epidemiology Erasmus MC University Medical Center Rotterdam the Netherlands; Meta Research Innovation Center at Stanford Stanford University Stanford USA

Department of Geriatrics 1st Faculty of Medicine Charles University and General University Hospital Prague Czech Republic; Faculty of Health and Social Sciences University of South Bohemia České Budejovice Czech Republic

Department of Internal Medicine Erasmus MC University Medical Center Rotterdam the Netherlands

Department of Internal Medicine Erasmus MC University Medical Center Rotterdam the Netherlands; Department of Orthopedics and Sports Medicine Erasmus MC University Medical Center Rotterdam the Netherlands

Department of Internal Medicine Erasmus MC University Medical Center Rotterdam the Netherlands; University of Clermont Auvergne Human Nutrition Unit INRAe CRNH Auvergne Clermont Ferrand France

Medical University of Graz Institute of Nursing Science Graz Austria

University of Clermont Auvergne Human Nutrition Unit INRAe CRNH Auvergne Clermont Ferrand France

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