Aging is accompanied by changes in body composition, such as an increase in fat mass (FM), a decrease in skeletal muscle mass index (SMMI) and muscle strength, combined with a chronic inflammatory process (CI). Determine the relationship between age and excess body fat with markers of chronic inflammation, skeletal muscle mass and strength. A cross-sectional alitical study was carried out in a convenience sample of adults 45 to 59years old (n = 100) and older adults 60 to 74years old (n = 133). All participants had their body composition measured with an impedance meter. They were subsequently divided into two groups: (i) with excess fat (WEF), (ii) without excess fat (NEF), in order to relate excess fat and age with inflammation, muscle mass and strength. NEF adults and older adults had similar values of SMMI (9.1 ± 1.5 vs. 8.8 ± 1.3, p > 0.05) and strength (28 ± 8 vs. 27 ± 8.6, p > 0.05). Likewise, WEF adults showed significantly lower values than NEF adults in the SMMI (7.9 ± 0.8 vs. 9.1 ± 1.5, p < 0.05) and strength (28 ± 8 vs. 22 ± 5, p < 0.001). Also, WEF older adults presented significantly lower values in the SMMI (15.9 ± 1.8 vs. 22.8 ± 5.1, p < 0.05) and strength (17.9 ± 4.8 vs. 27 ± 8.6, p < 0.001). Our findings suggest that excess fat mass is a risk factor that has a significantly greater influence than aging per se on the index of skeletal muscle mass and strength.