OBJECTIVE: Obesity has become a major public health problem worldwide and particularly in China. This study examined the secular trend of overweight and obesity in China over the past 100 years. METHODS: Nationwide data from the China Health and Nutrition Survey and the Chinese General Social Survey were used. A generalized binary mixed-effects model and a weighted quantile sum model were applied. RESULTS: From 1909 to 2021, the prevalence of overweight and obesity remained stable from 1909 to 1944, experienced a smooth increase from 1945 to 1959 followed by a decline between 1960 and 1974, continued to rise after 1975, and peaked in 2003. The prevalence of overweight (obesity) among Chinese adults increased by 2.68 (6.21) times, from 20.65% (3.10%) in 1993 to 55.33% (19.26%) in 2021, and cohorts born during the Chinese Cultural Revolution (1960-1974) exhibited the lowest risk of overweight and obesity, associated with low protein intake and high physical activity. Cohorts born during the Reform and Opening-Up period (1975-2003) showed a high risk of overweight and obesity related to favorable socioeconomic status and rapid urbanization. Persistent differences by sex and emerging differences by socioeconomic status in overweight and obesity prevalence were captured. CONCLUSIONS: Overweight and obesity trends in China have shown a distinctive increasing-decreasing-increasing pattern over the past 100 years. These patterns exhibit unique characteristics and are influenced by discernible social forces.