Intermittent fasting has been the subject of numerous studies in recent years prompting scientists to try and determine a safe fasting protocol that can work as an effective strategy for weight loss. The latest evidence, based on a large sample, may have the answer to one of the most asked questions about fasting: What is the best fasting window for intermittent fasting.

Led by the University of Granada in Spain and published by Nature.com, experts were keen to address the global issue of obesity. In the United States, almost one in three adults are overweight but the problem is not limited to North America. With many European counties displaying similar trends, health services around the world are stretched as ailments such as heart disease and type 2 diabetes become ever more prevalent. Since traditional diets generate such low scores of sustained success, doctors have long looked to intermittent fasting, otherwise known as time restricted eating, as a means of minimalizing meals.

The Optimum Eating Window for Intermittent Fasting

By working with 197 participants, one of the largest samples to date, scientists found that eating for 8 hours and fasting for 16 hours worked best, especially when paired with an early eating window of 9am to 5pm rather than a later period between noon to 8 p.m.. During the 12-week study, all of the participants who fasted for 16 hours lost an average of 3-4kg when compared to the group who had a 12-hour eating window, but the early fasting group was deemed best as they reduced subcutaneous fat to a greater extent. “The results show that the early fasting group significantly improved fasting glucose levels and overnight glucose compared to the other groups,” concluded the report.

Improving glucose regulation is important because this will in turn help to prevent diabetes and benefit out metabolic health. Dr Labayen, who is the principal investigator of the study explains that not eating during the evenings will allow the body greater time to digest and process nutrients, leading to this better regulation of blood glucose while reducing the risk of developing sugar related problems or other disorders.

In terms of safety, the scientists also noted that no serious adverse events were recorded during the trials. “Intermittent fasting is therefore presented as a safe and promising strategy for managing body weight and improving cardiovascular health in people who are overweight or obese,” concluded a write-up of the report by the University of Granada.