Objective Physical activity (PA) and sedentary behavior (SB) have been linked to adult adiposity. This research aims to explore 10‐year (2007‐2016) trends in obesity and abdominal obesity prevalence and associations with different types of PA and SB among US adults. Methods National Health and Nutrition Examination Survey (NHANES) data were used with 20‐ to 64‐year‐old adults (n = 20,360; mean age: 41.9 years; male: 50.5%; non‐Hispanic White: 64.3%). Sex‐ and sex‐ and race‐specific linear trends in the prevalence of obesity, abdominal obesity, and moderate and vigorous work‐ and recreation‐related PA and SB were estimated. Weighted logistic models explored the association between risk of obesity or abdominal obesity with each type of PA and SB by sex, adjusted for relevant confounders. Results There were significant increasing trends in obesity and abdominal obesity in both sexes and in Hispanic adults. Men at higher vigorous work‐related PA levels (P = 0.045) and women at higher moderate recreational‐related PA (P = 0.005) levels had decreased risk of abdominal obesity. Women at the highest versus the lowest level of SB had increased risk of abdominal obesity (P = 0.017). Conclusions There was a significantly reduced risk for abdominal obesity with a few types of PA among both sexes and an increased risk with SB among women only.