At Risk for Type 2 Diabetes? Limit Eating to Just 8 Hours Per Day, Research Finds

Restricting eating to an eight-hour window each day can significantly enhance blood sugar control in adults at risk of type 2 diabetes, a new study finds. According to research to be presented at the annual meeting of the European Association for the Study of Diabetes (EASD), the timing of the eating window—whether earlier or later in the day—does not influence these benefits.

“Our study found that restricting eating to a window of eight hours per day significantly improved the daily time spent in the normal blood glucose range and reduced fluctuations in blood glucose levels,” explains Kelly Bowden Davies, PhD, the study’s lead author from Manchester Metropolitan University. “However, altering the eight-hour restricted eating period to earlier or later in the day did not appear to offer additional benefits.”

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The benefits of time-restricted eating

The study, conducted as a randomized crossover trial, showed that adults who fasted for 16 hours daily experienced improvements in their blood glucose levels in as little as three days, regardless of when they started their eight-hour eating window. 

This study builds on previous research suggesting that time-restricted eating (TRE), which focuses on limiting eating periods without restricting calories or certain foods, can improve insulin sensitivity and glycated hemoglobin, a measure of average blood sugar levels. However, this new study was the first to assess the impact of TRE on glycemic variability—changes in blood glucose levels—while maintaining an energy balanced diet (ensuring participants’ caloric intake was equal to the amount of energy required for physical activity and essential bodily functions). 

“Many people find counting calories hard to stick to in the long term, but our study suggests that watching the clock may offer a simple way to improve blood sugar control in people at risk of type 2 diabetes, irrespective of when they have their eight-hour eating window, which warrants investigation in larger studies and over the longer term,” Davies noted. 

Researchers assigned 15 sedentary adults at risk of type 2 diabetes to two different time-restricted eating patterns: an early TRE (ETRE) regimen, allowing eating only between 8am and 4pm, and a late TRE (LTRE) regimen, with eating permitted between noon and 8pm. 

All participants followed each regimen for three days, with their energy intake matched to energy expenditure based on their age, weight, height, sex, and activity level. A standardized diet was provided during these periods, while participants maintained their usual eating habits during a habitual eating phase that spanned more than 14 hours a day.

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The study found that an eight-hour daily eating window significantly increased the time spent within a normal blood glucose range by an average of 3.3 percent compared to a habitual eating period of over 14 hours. It also reduced glycemic variability (blood glucose fluctuations) markers.

Despite these improvements, the study reported no significant differences in glycemic control between the early and late eating windows, suggesting that the benefits of TRE are derived from the 16-hour fasting period itself rather than the specific timing of the eating window.

Does a plant-based diet help reduce diabetes risk?

While the study participants did not adhere to a plant-based diet, prior research indicates that adhering to a whole-foods, plant-based diet can help reduce diabetes risk and even reverse type 2 diabetes.

According to a study published in the American Journal of Lifestyle Medicine last year, a low-fat, high-fiber plant-based diet rich in whole foods such as vegetables, legumes, whole grains, fruits, nuts, and seeds, significantly improved blood glucose control. Out of the 59 participants, 37 percent experienced full remission of their diabetes. 

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Meat consumption, however, has been proven to increase the risk of developing type 2 diabetes. A study led by researchers from Harvard T.H. Chan School of Public Health found that even moderate consumption of red meat increases the risk of type 2 diabetes. 

Researchers looked at data from over 216,000 participants collected over a period spanning up to 36 years. They discovered a strong correlation between red meat consumption, including both processed and unprocessed varieties, and an elevated risk of developing type 2 diabetes. Those with the highest red meat intake faced a 62-percent greater risk of developing the disease compared to those with the lowest consumption levels.