Extending overnight fasting to 12–16 hours for six weeks in middle-aged and older adults (aged 57–60 years, BMI 31 kg/m², HbA1c <6.5%) significantly improves glucose regulation during an oral glucose tolerance test, reducing blood glucose levels and increasing the insulinogenic index, indicating enhanced beta-cell function in response to glucose.

When food intake stops for 12 to 16 hours overnight, the pancreas gets a break from constantly releasing insulin, allowing beta-cells to reset and respond more strongly when glucose arrives. At the same time, the liver reduces its sugar production during the night, and the nervous system shifts into a rest-and-repair mode that lowers heart rate and blood pressure, helping the body use sugar more efficiently.