Regarding the weight loss dietary interventions with calorie restriction to 500- 600 kcal/day, three studies using hypocaloric diets for 8 to 10 weeks reported no significant effect of TCF7L2 rs7903146 on fasting glucose, insulin concentrations, insulin secretion, insulin resistance, and HOMA-β in overweight, obese, and metabolic syndrome subjects [28, 32, 44]. This evidence concerns the gene TCF7L2 and metabolic syndrome.