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The objective of this investigation is to study how excess body weight influences the energy cost of walking (Cw) and determine whether overweight and obese older adults self-select stride frequency to minimize Cw.Using body mass index (BMI), men and women between the ages of 65 and 80 yr were separated into normal weight (NW, BMI ≤24.9 kg·m−2, n = 13) and overweight–obese groups (OWOB, BMI ≥25.0 kg·m−2, n = 13). Subjects walked at 0.83 m·s−1 on an instrumented treadmill that recorded gait parameters and completed three 6-min walking trials; at a preferred stride frequency (PSF), at +10% PSF, and at −10% PSF. Cw was determined by indirect calorimetry. Repeated-measures ANOVA was used to compare groups, and associations were tested with Pearson correlations, α = 0.05.OWOB had 62% greater absolute Cw (301 ± 108 vs 186 ± 104 J·m−1, P < 0.001) and 20% greater relative Cwkg (3.48 ± 0.95 vs 2.91 ± 0.94 J·kg−1·m−1, P = 0.046) than NW. Although PSF was not different between OWOB and NW (P = 0.626), Cw was 8% greater in OWOB at +10% PSF (P < 0.001). At PSF, OWOB spent less time in single-limb support (33.1% ± 1.5% vs 34.9% ± 1.6 % gait cycle, P = 0.021) and more time in double-limb support (17.5% ± 1.6% vs 15.4% ± 1.4% gait cycle, P = 0.026) than NW. In OWOB, at PSF, Cw was correlated to impulse (r = −0.57, P = 0.027) and stride frequency (r = 0.51, P = 0.046).Excess body weight is associated with greater Cw in older adults, possibly contributing to reduced mobility in overweight and obese older persons.