['To examine if greater nutrition knowledge vs gains in knowledge promote more successful weight loss in low-income, overweight and obese mothers with young children.', 'A convenience sample of mothers and their children were measured for height and weight; mothers completed demographic and nutrition knowledge questionnaires pre- and post-intervention.', 'Participants (N=141) were recruited from government and public health clinics and elementary schools. Inclusion criteria for mothers were: family income <200% federal poverty level; overweight/obese; and Hispanic, African-American, or white race/ethnicity.', 'Eight weekly weight-loss classes emphasizing diet, physical activity, and behavior modification based on Social Cognitive Theory were administered to mothers.', 'Improvements in maternal nutrition knowledge and weight loss.', 'Paired-samples t tests, repeated measures analysis of variance, analysis of covariance, Pearson correlations, and chi(2) statistics.', 'Nutrition knowledge of mothers increased in all areas. Participants with weight loss > or =2.27 kg (responders) had greater knowledge than those who did not; however, the actual net gain was similar for those who lost and did not lose weight. Weight gainers only improved in two areas on the test, whereas weight-loss responders increased knowledge in all six. Responders appeared more cognizant of diet, weight loss, and health information.'] Is nutrition knowledge associated with greater weight loss in obese and overweight low-income mothers?