Therefore, the hypotheses for the present study were that in adults with obesity, long-term weight loss through caloric restriction will (i) decrease fasting and/or postprandial plasma LEAP2, (ii) which will positively correlate with decreases in weight, improvements in glucose and/or fat metabolism, while (iii) weight regain will increase fasting plasma LEAP2, and (iv) DJBL insertion will exaggerate the decrease in fasting and/or postprandial plasma LEAP2 due to loss of contact of ingested food with the duodenum/jejunum. This evidence concerns the gene LEAP2 and obesity due to melanocortin 4 receptor deficiency.