The purpose of this research was to develop, validate, and test an instrument to evaluate motivations to eat in low-income women during the early postpartum period. The instrument was also used in a sample of young college women to further validate the measure and explore determinants of eating in this population. In study 1, the Eating Stimulus Index was validated in 179 low-income women in early postpartum. Validity and reliability were determined via principal components analysis, internal consistency reliability, and test-retest reliability using a subgroup of 31 low-income new mothers. The factor analysis produced an eight factor structure with reliability coefficients ranging from 0.54-0.89. Convenience eating (r=-0.25, P<0.01), emotional eating (r=-0.17, P<0.05), and dietary restraint (r=-0.21, P<0.01) were significantly related to weight status. In study 2, the relationship between eating motivations and diet quality, determined via the Dietary Guidelines Adherence Index, was established in 115 low-income women in early postpartum. High diet quality was related to fruit and vegetable availability (r=0.25, P<0.01), convenience eating resistance (r=-0.36, P<0.001), and vegetable taste preference (r=0.23, P<0.05). Motivations to eat differed between overweight and obese women with the primary motivation being convenience eating and taste, respectively. In study 3, determinants of weight loss were examined in 58 low-income women in early postpartum participating in an 8-week weight loss intervention. Participants were evaluated at pre- and post-study for all measures. Factors related to weight loss included increases in dietary restraint, weight management skills, and weight loss self-efficacy and decreases in fruit juice servings, total energy, and discretionary energy intakes. After hierarchical regression analysis, improvement in weight loss self-efficacy was the most significant determinant (β=0.263, P<0.05) followed by decreases in discretionary energy intake (β=-0.241, P<0.05). In study 4, determinants of diet quality were assessed in a sample of 88 young college women using the Eating Stimulus Index. Low diet quality was associated with poor fruit and vegetable availability, convenience eating resistance, vegetable taste preference, and weight management self-efficacy, while high diet quality was related to increased frequency of meals prepared at home and decreased frequency of meals consumed at fast food restaurants. / text