This regulation/impaired regulation of CPT1A response to ATRA, more related to HDL than to BMI is of interest, as it could be used as a new marker to diagnose metabolic risk with independence of the presence of overweight or obesity, as it is well known that also normal-weight individuals can have increased metabolic syndrome risk [55]. This evidence concerns the gene CPT1A and obesity due to melanocortin 4 receptor deficiency.