In the current study, our initial analysis found a negative association between anaemia (i.e., anaemia and normocytic anaemia) and overweight/obesity in contrast to previous studies, some of which failed to report any association between anaemia and overweight/obesity [43,44,45], whereas others detected a positive association between Hb concentration and BMI [43,44]. Here, GSTM1 is linked to obesity due to melanocortin 4 receptor deficiency.