Weight loss and diabetes remission after SG DJB are mainly because of hormonal and genetic changes. Role of food restriction or mal-absorption is secondary. After this operation Ghrelin hormone levels come down as fundus of the stomach is removed. GLP 1, Peptide YY hormone levels increase as food directly enters from 1st part of duodenum into mid jejunum and rapidly reaches distal ileum (last part of small intestine). Food doesn’t enter the remaining duodenum and proximal jejunum. So levels of anti incretin hormones come down. There will be more than 200 hormone changes after surgery. Removal of body of stomach alters several genes involved in energy balance. These hormonal and genetic changes reduce appetite, increase energy expenditure and reset the ‘fat mass’ to a lower level, resulting in weight loss. Same hormonal changes are responsible for type 2 diabetes remission. Ghrelin and anti incretins act against insulin. As levels of these hormones come down, insulin resistance comes down. Since GLP 1 hormone is increased, insulin production increases and insulin resistance comes down. Diversion of biliopancreatic juices also contributes to the metabolic effects of this surgery.