Increasing obesity in low- and middle-income countries is well documented in cross-sectional studies. However, few longitudinal studies identify factors that influence individual weight gain patterns over time in relation to the major social and economic changes that now characterize these settings. This study uses data from adult Filipino women participating in the Cebu Longitudinal Health and Nutrition Survey from 1983 to 2005. A sample of 3005 women contributed 1-8 observations each. Longitudinal mixed effects models identified how age and secular weight trends related to underlying effects of urbanization and changing household socioeconomic status (SES) and to proximate individual effects of reproductive history, diet, and occupational physical activity. The 23-y secular trend in weight amounted to nearly 10 kg. Younger women gained more weight than older women (12.4 kg in those < 20 y old in 1983 vs. 4.9 kg in those > 35 y). Periods of more rapid weight gain corresponded to periods of rapid increase in SES and urbanization. Weight was positively related to energy intake, percentage of calories from protein, and more sedentary occupations, but negatively related to months pregnant and lactating and postmenopausal status. These effects all varied with age and over time. The trends contributed to a 6-fold increase in prevalence of overweight and an increasing number of women who have or are likely to develop obesity-related metabolic diseases. The trends are highly relevant for health policy and preventive health measures in the Philippines and other countries now facing the dual burden of over- and undernutrition.