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Can Restricting Eating Time Help Control Blood Sugar?

Restricting eating time to early in the day may improve insulin sensitivity, reduce blood sugar response to meals and help with weight control.

People at risk of developing type 2 diabetes may be able to reverse this process by restricting eating time to a nine-hour period every day. One reader embraced this approach and was thrilled with the results.

Should You Consider Time Restricted Eating?

Q. Due to a bad A1c report, I wanted to improve my blood sugar profile. I began Time Restricted Eating (TRE), and my blood sugar readings improved greatly. To my surprise, I also lost 24 pounds.

That was a year and a half ago, and my weight only ever varies by about one pound. It is just amazing and the easiest thing I’ve ever done.

We eat a large breakfast at 10 AM and dinner at 6 PM. If I want a snack during my “eating hours,” I have one. I do eat fewer carbs than some people and have for years, but we still had a small piece of dessert every day during the first year. We keep chocolate on hand and eat a square if we want one.

I have always walked a couple of miles per day, and I have continued this through TRE. My A1c is now in the prediabetic range, and my weight stays the same all of the time.

Because we are never hungry, I don’t call this a diet. Instead, I call it an “eating plan.” We read Dr. Jason Fung’s book The Diabetes Code, and it has been a life changer. He offers good explanations of why TRE is good for you and your metabolism.

A. We appreciate hearing of your success. The most recent research on time restricted eating was published in JAMA Network Open (Oct. 27, 2023).  The investigators recruited 75 people with type 2 diabetes and assigned them to count calories (eating 25 percent less than before the trial began), eat only between noon and 8 pm or do nothing different (control group).

People in the time-restricted eating group lost more weight and found it easier than counting calories. Both groups lowered their HbA1c levels, a measure of blood glucose over several weeks. That correlates well to your experience.

Previous Research on Restricting Eating Time:

Researchers at the University of Adelaide in Australia conducted a pilot study on time restricted eating to help control blood sugar. (Obesity, April 19, 2019).

How They Conducted the Study:

The fifteen men in the study wore continuous glucose monitors for a week before the study began and for each of two weeks of time-restricted feeding. For one of those weeks, the men could eat what they chose between 8 am and 5 pm. During the other, however, they ate only between noon and 9 pm.

During the week of eating early, their blood sugar was significantly lower than during the pre-study assessment. After both weeks of cutting meal time, the men had much better blood glucose responses to a test meal. Most importantly, they did not have to cut calories to achieve this goal.

Follow-up on the Pilot Study:

Some of the same scientists who conducted this pilot study have followed up with a larger study that lasted longer (Nature Medicine, April 2023). It also included an aspect of intermittent fasting. For that subsequent research, they recruited 209 middle-aged adults at risk of type 2 diabetes. They assigned the volunteers to one of three groups. One group ate 30% of their caloric requirement between 8:00 am and 12:00 pm and nothing after noon on three days a week. A second group restricted their energy intake to just 70% of their requirements, day in and day out. The third group, serving as the controls, were provided with a booklet on weight loss.

For the first six months, the participants in the two intervention groups got intensive nutrition support. The scientists collected data on everybody in the study for an additional year. At the six-month mark, people practicing the intermittent fasting had better blood glucose control. However, the difference between calorie counting and restricting eating time was no longer significant at 18 months.

The investigators write:

“In conclusion, incorporating advice for meal timing with prolonged fasting led to greater improvements in postprandial glucose metabolism in adults at increased risk of developing type 2 diabetes.”

Previous Research on Cutting Meal Time:

This is not the first study to show that limiting food intake to just part of the day has metabolic benefits. Previously, investigators found that people who eat in the morning and stop at mid-day have better blood pressure and insulin sensitivity as well as lower oxidative stress. In addition, some studies have shown that restricting eating time (and therefore extending fasting time) can help people lose weight (Proceedings of the Nutrition Society, April 26, 2019).

Learn More:

You may wish to listen to some of our interviews with scientists who have examined the effects of limiting food intake to certain parts of the day. We spoke with Dr. Jason Fung about intermittent fasting to help control blood sugar in Show 1143: Can You Control Your Blood Sugar by Fasting?  In addition, we spoke earlier with Dr. Marie St. Onge in Show 1094: Does It Matter When You Eat?

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About the Author
Terry Graedon, PhD, is a medical anthropologist and co-host of The People’s Pharmacy radio show, co-author of The People’s Pharmacy syndicated newspaper columns and numerous books, and co-founder of The People’s Pharmacy website. Terry taught in the Duke University School of Nursing and was an adjunct assistant professor in the Department of Anthropology. She is a Fellow of the Society of Applied Anthropology. Terry is one of the country's leading authorities on the science behind folk remedies..
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