The self-perception of weight and weight loss attempts might promote weight loss and maintenance. To examine trends in current measured body mass index (BMI) and weight, self-reported weight, self-perceived weight status, weight loss attempts, and weight loss strategies among adults in the United States. This national cross-sectional study used data from continuous National Health and Nutrition Examination Survey (NHANES) data sets (1999-2000 to 2015-2016). Participants were US residents older than 20 years. Data were analyzed from January 2018 to December 2018. Current measured BMI and weight, self-reported weight, self-perceived weight status, weight loss attempts, and applied weight loss strategies. Adjusted, self-reported, prior-year weight was calculated using correction equations that considered age, sex, race/ethnicity, and quartile of self-reported prior-year weight. Data were collected from 48 026 participants (19 792 [41.2%] aged 40-64 years; 24 255 [50.5%] women; 21 725 [45.2%] white) through 9 surveys from 1999-2000 to 2015-2016. Increasing trends were observed in current measured BMI (difference, 1.20; 95% CI, 0.92-1.47; P for trend < .001), current measured weight (difference 2.77 kg; 95% CI, 1.92-3.61 kg; P for trend < .001), adjusted, self-reported, prior-year weight (difference, 2.36 kg; 95% CI, 1.52-3.21 kg; P for trend < .001), and the difference between measured and adjusted self-reported weight (difference 0.70 kg; 95% CI, 0.34-1.07 kg; P for trend < .001). During this period, the proportion of overall participants who had attempted to lose weight increased from 34.3% to 42.2% (difference, 8.0%; 95% CI, 4.1%-10.5%; P for trend < .001). The most commonly reported weight loss strategies with the most rapidly increasing prevalence during the study period were reduced food consumption (21.2%-31.9%; difference, 11.1%; 95% CI, 8.2%-13.3%; P for trend < .001), exercise (18.2%-31.5%; difference, 14.4%; 95% CI, 11.3%-16.9%; P for trend < .001), and frequent water intake (0.2%-26.3%; difference, 26.2%; 95% CI, 24.1%-29.0%; P for trend < .001). Between 2005-2006 and 2015-2016, increases were also observed for the reported consumption of more fruits, vegetables, and salads (0.1%-29.4%; difference, 30.3%; 95% CI, 28.1%-31.2%; P for trend < .001), changing eating habits (0.3%-20.5%; difference, 20.2%; 95% CI, 19.1%-22.3%; P for trend < .001), and the consumption of less sugar, candy, and sweets (0.2%-20.9%; difference, 21.7%; 95% CI, 19.3%-22.6%; P for trend < .001). In this cross-sectional study, our data indicated an increasing trend in the proportion of participants who attempted to lose weight and a parallel increasing trend in current measured BMI and weight among adults in the United States.