FTO and obesity due to melanocortin 4 receptor deficiency: While the variations of the obesity-associated gene FTO were reported to be associated with BC risk in some populations (Zeng et al., 2015[40]; Chen et al., 2019[8]; Sadim et al., 2017[32]; Zhao et al., 2016[42]; Zhang et al., 2014[41]), they could not be associated with some others (da Cunha et al., 2013[9]; Jafari Nedooshan et al., 2017[11]; Mojaver et al., 2015[26]).