Conclusions: These results demonstrate that D-allulose, D-tagatose, and D-sorbose, which are low-calorie rare sugars classified as ketohexoses, suppress food intake through promoting GLP-1 secretion, showing their potential to prevent and/or ameliorate type 2 diabetes, obesity and related diseases. This evidence concerns the gene GCG and obesity due to melanocortin 4 receptor deficiency.