This study examined the relation between household food security status and current measured weight and change in self-reported weight over 12 mo using data from the 1999–2000 and 2001–2002 National Health and Nutrition Examination Surveys. Current measured BMI categories were as follows: underweight (<18.5 kg/m²), overweight (≥25 kg/m²), and obese (≥30 kg/m²). Change in self-reported weight used 2 cut-off points, i.e., a gain/loss of at least 2.27 kg (5 lb) and at least 4.54 kg (10 lb). Household food security categories were as follows: fully secure, marginally secure, insecure without hunger, and insecure with hunger. Multivariate analyses were adjusted for race/ethnicity, household income, education level, and current health status. Compared with women in households that were fully food secure, women in households that were marginally food secure [odds ratio (OR) 1.58] and food insecure without hunger (OR 1.76) were significantly more likely to be obese. Compared with women in households that were fully food secure, those in households that were marginally food secure were significantly more likely to gain at least 4.54 kg (OR 1.68). Compared with men in households that were fully food secure, men in households that were marginally food secure were more likely to be obese and to gain at least 4.54 kg, but these effects were smaller in magnitude than those for women and insignificant in some specifications. This study corroborates previous cross-sectional associations between intermediate levels of food insecurity and obesity for women, and it finds an association between intermediate levels of food insecurity and 12-mo weight gain for women. [ABSTRACT FROM AUTHOR]