Koster A, Penninx BW, Newman AB, Visser M, van Gool CH, Harris TB, van Eijk JT, Kempen GI, Brach JS, Simonsick EM, Houston DK, Tylavsky FA, Rubin SM, Kritchevsky SB. Lifestyle factors and incident mobility limitation in obese and non-obese older adults. Obesity (Silver Spring). 2007 Dec; 15(12):3122-32.