Type of Intermittent Fasting Helps Manage Blood Sugar Levels

  • A small new study links intermittent fasting to better blood sugar management.
  • Eating 80% of calories before 1 p.m. was more effective at blood sugar management than following a regular eating pattern.
  • Experts say more research is needed before this strategy can be recommended—and it could pose some problems for certain groups.

A new study finds that a restricted eating plan that involves eating the bulk of your calories earlier in the day may help with blood sugar management—and reduce the chances of developing type 2 diabetes in people at risk of the condition.

The study, which was just presented at the Endocrine Society’s annual meeting, followed 10 people who had obesity and high blood sugar levels.

The researchers had participants follow either an early time-restricted feeding pattern, where 80% of their calories were consumed before 1 p.m., or a normal eating pattern, where half the day’s calories were eaten after 4 p.m. (Food was provided for them.) The study participants did one eating pattern for a week and then the other for an additional week. They also wore continuous blood sugar monitors (CGMs) throughout the study.

While the study participants’ weight stayed constant throughout the study, blood sugar levels were more consistent and less elevated when they got the bulk of their daily calories before 1 p.m.

This eating pattern and its impact on blood sugar “may help prevent those with prediabetes or obesity from developing type 2 diabetes,” says lead study author Joanne Bruno, M.D., Ph.D., an endocrinology fellow at NYU Langone Health. (Prediabetes, in case you’re not familiar with it, is a condition where blood sugar levels are higher than normal but not high enough to be classified as type 2 diabetes.)

But why might eating the bulk of your calories during a certain window be helpful, especially before 1 p.m.? Dr. Bruno says her team is still exploring this, but there are some theories. Here’s what we know so far.

Why might eating most of your calories early be helpful for blood sugar management?

It’s important to note that the study didn’t explore why this association exists—it just found a link. Still, there are a few theories.

“Many aspects of our health and within our body fluctuate according to certain circadian patterns,” Dr. Bruno says. Taking in more calories during times of day when you tend to be most active may help synch up your hormone and metabolic health, she says.

“This approach might help lower the risk of developing type 2 diabetes because prolonged periods of elevated blood sugar can lead to insulin resistance, a key factor in the development of type 2 diabetes,” says Scott Keatley, R.D., co-owner of Keatley Medical Nutrition Therapy. “By reducing the time that blood sugar is above normal, time-restricted eating could potentially prevent the progression from prediabetes to type 2 diabetes.”

Your pancreas, which makes insulin that helps carry sugar from your blood into your cells, is also more active during the day, explains Pouya Shafipour, M.D., a board-certified family and obesity medicine physician, of Providence Saint John’s Health Center in Santa Monica, CA. “You have more insulin sensitivity during the day and less at night,” he says. “If you frontload your calories, they will metabolize better and fluctuations will go down significantly.”

Having a larger window of time where you’re not eating as much also “gives your body time for blood sugar levels to come down,” says Jessica Cording, R.D., author of The Little Book of Game-Changers.

At a basic level, sticking to a window where you eat most of your calories “can help prevent eating habits that contribute to poor food choices and health, such as late-night snacking and eating too many calories in one day,” says Beth Warren, R.D., author of Secrets of a Kosher Girl.

Late-night snacking and mindless eating also tend to be more common as the day stretches on, says Keri Gans, R.D., author of The Small Change Diet. “Perhaps there is better blood sugar control because there is a greater chance of poorer food choices made the longer the day progresses,” she says.

Experts say this strategy isn’t for everyone

Intermittent fasting and time-restricted eating may not be suitable for those with a history of disordered eating. Other groups that might not benefit from this strategy include those with type 1 diabetes and those with type 2 diabetes that use insulin.

Dr. Bruno’s study specifically looked at people who had obesity and high blood sugar levels—not those who already had type 1 or type 2 diabetes.

Patients who rely on insulin for blood sugar management should be wary of any type of fasting, Keatley says. “Intermittent fasting may not be safe for insulin-dependent diabetics because it can lead to periods of both low and high blood sugar,” he says. “Insulin-dependent diabetics need to carefully balance their food intake and insulin administration; If food intake becomes too unpredictable, it could lead to dangerous fluctuations in blood sugar levels.”

If you’re not dependent on insulin for blood sugar management but you’re concerned about your diabetes risk, Dr. Bruno says it’s a good idea to consult with a doctor before making any major dietary changes.

When it comes to putting an eating plan like this into place, Cording recommends making sure each meal and snack contains protein, fat, and fiber. “All meals should incorporate these nutrients for blood sugar management,” she says.

Dr. Bruno and her team plan to do long-term studies on early intermittent fasting diets to learn more.

If you believe you are struggling with an eating disorder and need support, call the National Eating Disorders Association helpline at (800) 931-2237. You can text HOME to 741741 to message with a trained crisis counselor from the Crisis Text Line for free.

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Korin Miller is a freelance writer specializing in general wellness, sexual health and relationships, and lifestyle trends, with work appearing in Men’s Health, Women’s Health, Self, Glamour, and more. She has a master’s degree from American University, lives by the beach, and hopes to own a teacup pig and taco truck one day.

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