Fasting Later in Day Might Be Key to Controlling Blood Sugar: Study

THURSDAY, June 15, 2023 -- Intermittent fasting is all the rage due to the lengthy list of health benefits associated with this style of eating.

Now, a new, small study suggests that one type of intermittent fasting — early time-restricted eating — may be key for preventing type 2 diabetes in people who are at high risk for the blood sugar disease.

The study included 10 people with prediabetes and obesity. Prediabetes refers to when blood sugar levels are higher than normal but not high enough to be defined as diabetes. Obesity is also considered a major risk factor for type 2 diabetes.

Folks in the study ate 80% of their daily calories before 1 p.m (early time-restricted feeding) or half of their calories after 4 p.m (usual eating) for one week, and then they switched to the opposite group during the second week.

Early time-restricted feeding reduced blood sugar fluctuations and decreased the time that blood sugar was above normal levels throughout the day, and this was independent of any weight loss.

“There is a large body of evidence that eating early in the day is beneficial for metabolic health, and many people experience weight loss even though their calories may not be restricted, but it was unclear whether these benefits were related to weight loss or independent, and this study suggests they are independent,” said study author Dr. Joanne Bruno. She is an endocrinology fellow at NYU Langone Health in New York City.

“This may be a helpful dietary strategy for diabetes prevention,” Bruno said.

Time-restricted eating doesn’t require calorie counting, she said. “It is just regular eating with the majority of calories consumed early in the day, which is easier to follow than other types of programs.”

The trial results were presented Thursday at the Endocrine Society’s annual meeting, in Chicago. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.

Experts not involved with the study pointed out that longer, larger studies are needed before any conclusions are drawn, and they noted that many people won’t want to limit their eating to this early window of time.

This study “adds some weight to the long-held idea to avoid eating before bed, but it will be difficult for most people to minimize eating after 1 p.m.,” said Dr. Scott Kahan, director of the National Center for Weight and Wellness, in Washington, D.C.

The human body is much more insulin-sensitive in the morning, explained Krista Varady, a professor of nutrition at the University of Illinois at Chicago. “[We] can put away sugar much better when we wake up, and then the ability to put away sugar slowly decreases over the course of the day,” she said. “It would make sense that consuming most of our calories earlier in the day would be good for blood sugar regulation.”

Varady said that the main reason intermittent fasting produces metabolic improvements is because people lose weight and belly fat. “Losing weight has a downstream effect of improving cholesterol levels, blood pressure, and blood sugar regulation,” she said.

The study did have some limitations, including its small size and short duration, she noted.

“While eating most of our food earlier in the day may be helpful, we still need more studies to confirm this, but we also need to consider social eating,” Varady added. “I don't think most Americans will adopt early eating patterns, as it would make it too difficult to socialize.”