INS and obesity due to melanocortin 4 receptor deficiency: Finally, we review the brain MRI literature for “indirect studies” on adult obesity controlled for metabolic health, namely studies investigating the effects of obesity (either dichotomic or continuous indices) stratified by metabolic control (mainly glucose tolerance and/or insulin resistance, cholesterol and blood pressure), or controlling for possible obesity-related comorbidities as confounders (Section “3.3.2 Indirect studies”).