Over the past three years, Oumoul and her family have devoted themselves to educating the villagers about preventing and treating malaria.

The advice is certainly not a quick fix or a guarantee, but Dr. Kessler said that educating himself in the course of writing the book had helped him gain control over his eating.

But a new study of remittances sent home by Ghanaian migrants suggests that on average they transfer enough over their working lives to cover the amount spent on educating them several times over.