Eating Earlier in the Day Can Improve Blood Sugar Levels, Study Finds

This content originally appeared on Everyday Health. Republished with permission.

By Lisa Rapaport

People with obesity and prediabetes who eat most of their meals within the first eight hours of the day may be able to lower their blood sugar levels even if they don’t lose weight, a small study suggests.

For the two-week study, researchers examined how the timing of meals impacted blood sugar in 10 participants with obesity and prediabetes, a condition that’s diagnosed when people have blood sugar that’s slightly elevated but not high enough to become full-blown type 2 diabetes.

All of the participants spent one of the weeks following their usual eating pattern, with half of their daily calories consumed after 4 p.m., and the other week doing a type of intermittent fasting known as early time-restricted eating where they ate 80 percent of their calories before 1 p.m.

Each participant received prepared meals with enough calories for them to maintain their current weight, and they all wore continuous blood sugar monitors throughout the study.

During the week of early time-restricted eating, participants had significantly less time when their blood sugar climbed above a healthy range than they did during the week when their meal timing was designed to mimic their usual eating habits, according to study results presented at the Endocrine Society’s annual meeting.

“This type of feeding, through its effect on blood sugar, may prevent those with prediabetes or obesity from progressing to type 2 diabetes,” lead study author Joanne Bruno, MD, PhD, an endocrinology fellow at New York University Langone Health in New York City, said in a statement.

Why Is Prediabetes a Concern and How Can You Prevent It?

Roughly 1 in 3 American adults have prediabetes, according to the Centers for Disease Control and Prevention (CDC). The condition is more common among people with obesity and among individuals who are 45 or older.

Regular physical activity and modest weight loss can both help prevent prediabetes and keep it from progressing, says the CDC. For a 200-pound person, losing 10 pounds (5 percent of their body weight) may help lower the risk. So can getting at least 150 minutes a week of brisk walking, or about a half hour a day, five days a week, the CDC recommends.

As for intermittent fasting, researchers like the ones behind the NYU study are investigating its varying impacts on obesity and prediabetes, and whether any particular time-restricting strategies do the most to improve health for individuals with these conditions.

When people see blood sugar improvements with intermittent fasting, it’s usually because they lose weight and what’s known as visceral fat — belly fat that can accumulate around organs like the stomach, liver, and intestines — says Krista Varady, PhD, a nutrition professor at the University of Illinois in Chicago, who wasn’t involved in the NYU study.

“Losing weight has a downstream effect of improving cholesterol levels, blood pressure, and blood sugar regulation,” Dr. Varady says.

The new study was too small and too brief to draw broad conclusions about whether early time-restricted eating might also help reverse prediabetes or stop it from progressing to type 2 diabetes, Varady adds. And more research is also needed to see if it’s possible that this type of intermittent fasting might help lower blood sugar even if people don’t lose weight, she says.

Is Early Time-Restricted Eating Worth a Try?

While there’s no harm in trying intermittent fasting for most people with obesity who don’t have other medical conditions, people who already have type 2 diabetes shouldn’t eat this way without consulting a doctor first, Varady advises. It’s also not a good idea for children under 12, people over 70, or individuals who are underweight or have eating disorders to eat this way.

Even when people do try intermittent fasting, the early time-restricted eating pattern used in the study might be hard for a lot of people to manage, Varady says.

“Most people prioritize eating meals in the evening with their families and friends,” Varady says. “So, I don’t think most Americans will adopt early eating patterns as it would make it too difficult to socialize.”

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