Long-term (10-year) ketogenic diet therapy in people with type 1 diabetes is possible and has a dual metabolic benefit by improving glycemic control 10-year mean HbA1c 5.5%/36.6 mmol/mol) in conjunction with a 43% decrease in insulin use, independent of changes in body mass/composition, total daily energy intake, or physical activity. Here, INS is linked to type 1 diabetes mellitus.