The present study aimed to investigate the possible changes in anthropometric and biochemical parameters in low-income women living in the outskirts of Maceió (northeast Brazil), and to explore the possible role of dietary intake and physical activity in these changes. A prospective longitudinal study was conducted in a cohort of mothers of malnourished children who attended the Center for Nutritional Recovery and Education, an outreach programme of the Federal University of Alagoas. Socio-economic, anthropometric, biochemical and dietary intake data were assessed at baseline and after a follow-up period of 4 years. Energy expenditure (using doubly labelled water) and physical activity (using triaxial accelerometers) were assessed only in a subgroup of women after 4 years. A total of eighty-five women were assessed. Participants showed an altered biochemical profile, increased systolic blood pressure, decreased thyroid hormone levels, and body-weight gain. However, dietary intakes of the participants did not include large quantities of highly processed and high-glycaemic index foods. The energy intake of the participants did not differ from their total energy expenditure (7990·3 (7173·7–8806·8) v. 8798·1 (8169·0–9432·4) kJ, respectively; P= 0·084). Multivariate analyses showed a significant effect of time spent watching television (β = 0·639 (0·003 to 1·275); P= 0·048) and dietary diversity score (β = − 1·039 ( − 2·010 to − 0·067); P= 0·036) on weight gain. The present study indicates that poor women, who are mothers of malnourished children and have a reasonably balanced dietary intake, exhibit weight gain and are at risk of developing chronic diseases.