Interesting issue. I don't know the answer to your first question, which would need to be resolved empirically. This could be done by looking at weight data for Fulani newborns. Physical activity and morphology cannot explain higher rates of low birth weight. High disease burden could, either because the disease causes prematurity, as some infections do, or retards the growth of the fetus, as malaria can.,

High rates of LBW is seen in other population groups also where you have reasons ranging from individual constitutions, inadequate quality of diets, some un-discovered endemicity of certain conditions leading to prematurity, anxiety and stress coming out of sustinance can result LBW...traditionally Fulani communities predominantly eat millet and very rarely eat meat..suggest exploring further if the areas has food secure environment and also compare and contrast weight data of new borns born to primi gravida and multi gravida with differant age groups.