CYP1A2 and obesity due to melanocortin 4 receptor deficiency: All were non-smokers and had BMIs <26, so expected relationships such as smoking inducing CYP1A2 activity (Anderson and Chan, 2016; Parra-Guillen et al., 2017) or obesity inhibiting CYP activity (Zarezadeh et al., 2021) could not be assessed.