Seven out of twelve studies that measured Hb did not show any association between Hb and overweight/obesity(18,25–27,42,47,51), three found an increase of Hb among overweight/obese women(28,44,46) and the rest (n 2) did not test the association(48,50). The gene discussed is GSTM1; the disease is obesity due to melanocortin 4 receptor deficiency.