To study individual determinants of differential benefit from the Senegal Community Nutrition Project (CNP) by monitoring improvement in children's weight-for-age index (WA) or underweight status (WA  < –2 Z-scores) during participation.

A follow-up study using the CNP child monitoring data. Linear general models compared variations in WA according to 14 factors describing the beneficiaries and CNP services.

Poor neighbourhoods of Diourbel, a large city in Senegal, West Africa. Over a 6-month period, the CNP provided underweight or nutritionally at-risk 6–35-month-old children with monthly growth monitoring and promotion and weekly food supplementation, provided that mothers attended weekly nutrition education sessions.

All the children who participated in the first two years of the project (n = 4084).

Mean WA varied from − 2.13 (standard deviation (SD) 0.82) to − 1.58 (SD 0.81) Z-scores between recruitment and the end of the follow-up. The lower the child's initial WA, the greater was their increase in WA but the lower was the probability of recovery from underweight. Only 61% of underweight children recovered. Six months of CNP services may not be sufficient for catch-up growth of severely underweight children. The number of food supplement rations received was not a direct indicator of the probability of recovery. After adjustment for services received and initial WA, probability of recovery was lower in girls, in younger children, in twins and when mothers belonged to a specific ethnic group.

Determinants of benefit from CNP differed from the risk factors for underweight. Identification of participants with a lower probability of recovery can help improve outcome. Moreover, an explanation for the lack of recovery could be that many underweight children are stunted but not necessarily wasted.