To determine the effects of a 6-month supervised low-volume resistance training (RT) program (1 set, 85–90%, one repetition maximum, 1RM, 3 d·wk−1) on muscular strength (1RM) and skeletal muscle mass (SMM) in previously sedentary, overweight men on an ad libitum diet. Nineteen men were randomly assigned to a control (CON, n = 8) or RT (n = 11) group. The exercise protocol consisted of 5 upper- and 4 lower-body exercises using weight machines. CON maintained their sedentary lifestyle. One RM for upper body (chest press [CP] + lat pull-down [LPD]) and lower body (leg press [LP]) and SMM were assessed at baseline, and at 3 and 6 months. Adherence was 96 ± 2% with an average time to complete each exercise session of 15 ± 2 minutes. Volume completed per exercise session significantly increased from baseline (2,812 ± 670 kg) to 6 months (6,411 ± 2,128 kg). There was a group by time interaction in 1RM for CP, LPD, and LP. Upper-body strength increased significantly (p < 0.001) (31.3 ± 9.3%) from baseline to 3 months and from 3 to 6 months (17.9 ± 8.7%). Lower-body strength also increased significantly from baseline to 3 months (17.8 ± 16.6%) and from 3 to 6 months (32.0 ± 33.7%). No changes in upper- or lower-body strength occurred in the CON group. There was no group by time interaction for SMM (CON, 34.5 ± 2.9 kg vs. RT, 34.2 ± 2.9 kg; p > 0.05) or for energy intake (p > 0.05). In conclusion, a single set resistance training program at 85% of 1RM, 3 d·wk−1 resulted in continued increases in muscular strength and a very high adherence rate over a 6-month period in sedentary, overweight men independent of significant changes in SMM. This training protocol may increase adherence and produce long-term increases in muscular fitness as part of an adult fitness program.