The Transcription factor 7-like 2 gene (TCF7L2) encodes a protein that has been implicated in blood glucose homeostasis (balance). TCF7L2 gene variations are strongly associated with type 2 diabetes and insulin resistance. TCF7L2 genetic variations have also been associated with body mass index (BMI) and cardiometabolic syndrome.
The T-allele indicates an increased risk and therefore should reduce the fat in their diet. A low-fat diet with low GI carbs is best suited to this genotype.