ABSTRACT: BACKGROUND:Food-assisted maternal and child health and nutrition (FA-MCHN) programs are widely used to reduce household food insecurity and maternal and child undernutrition in low- and middle-income countries. These programs, however, may unintentionally lead to excessive energy intake and unhealthy weight gain, especially in food-secure populations. OBJECTIVE:We evaluated the impact of an FA-MCHN program implemented in Guatemala on maternal weight from pregnancy to 24 mo postpartum. The program was earlier shown to reduce stunting. METHODS:We used a longitudinal, cluster-randomized controlled trial with arms varying in family ration size [full (FFR), reduced (RFR), none (NFR)] and individual maternal ration type [corn-soy blend (CSB), lipid-based nutrient supplement (LNS), micronutrient powder (MNP)]: A: FFR + CSB; B: RFR + CSB; C: NFR + CSB; D: FFR + LNS; E: FFR + MNP; F: control. Weight was measured during pregnancy and at 1, 4, 6, 9, 12, 18, and 24 mo postpartum. We used linear mixed models controlling for pregnancy weight with random cluster and mother effects. Data on 3535 women were analyzed. RESULTS:Significant (P < 0.05) or marginally significant (P < 0.10) effects of 0.50-0.65 kg were found at all time points (except 9 mo) in arm A. Similar-sized effects were found in arms B (1, 4, 6, and 12 mo) and C (1 and 12 mo). Marginally significant effects (0.51-0.66 kg) were found in arm D (1, 6, 9, and 12 mo); in arm E, marginally significant effects (0.48-0.75 kg) were found from 6 to 24 mo. CONCLUSIONS:The effect on maternal postpartum weight is of concern because of the high existing prevalence of overweight. Programs need to include "double-duty" objectives and actions, to ensure that addressing child undernutrition does not exacerbate the problem of unhealthy weight gain. This trial was registered at clinicaltrials.gov as NCT01072279.