Intermittent Fasting Can Slash Diabetes and Heart Disease Risk

Key Takeaways

• Time-restricted eating can improve blood sugar and cholesterol levels in people with a set of risk factors known as metabolic syndrome, according to recent research.
• People who followed a time-restricted eating schedule lost weight and reduced calorie intake without strict diet rules.
• People should consult their doctor before trying time-restricted eating.

People with risk factors that increase the likelihood of a heart attack , stroke , or type 2 diabetes may be able to slash their risk with a form of intermittent fasting known as time-restricted eating.

Adults with high blood pressure, elevated blood sugar levels, abnormal LDL cholesterol levels, extra abdominal fat, or other aspects of metabolic syndrome who narrowed their daily eating window saw improvements in just three months, a new study found.

The findings suggest that time-restricted eating is a feasible and effective way to improve multiple aspects of cardiometabolic health, especially blood sugar control and cholesterol, even if people are already on medications, says the lead author, Emily Manoogian, PhD , a postdoctoral fellow and researcher at the Salk Institute at the UC San Diego School of Medicine.

"Although this study was done in adults with metabolic syndrome, based on this and other findings, it can also help improve prediabetes, high blood pressure, high cholesterol, or elevated weight, and likely many more health issues," says Dr. Manoogian.

More than 1 out of 3 adults in the United States have metabolic syndrome, which significantly raises a person's risk of heart disease, stroke, and type 2 diabetes.

Study Subjects Had an 8- to 10-Hour Eating Window

For the study, researchers randomly placed a total of 108 adults with metabolic syndrome into either the time-restricted eating group or a control group. The group was 51 percent women with an average age of 59 years. The average weight was 196 pounds, and the average BMI was about 31.

Unlike most trials on time-restricted eating, this one included people who were taking medications for metabolic syndrome, such as cholesterol lowering or blood-pressure lowering drugs.

Although both groups received nutritional counseling on the Mediterranean diet , the intervention didn't limit what or how much people ate, and physical activity wasn't tracked. All participants logged their meals using a mobile app.

The study participants customized their time-restricted eating windows to their individual eating habits, sleep/wake times, and personal commitments. The resulting eating schedule had each participant reduce their eating window by about 4 hours to a consistent 8 to 10 hours per day, beginning at least one hour after they woke up and ending at least three hours before they went to sleep.

The personalized approach made the intervention easier for participants to complete, compared with other intermittent fasting studies, which typically assign the same strict time window to all participants, says Manoogian.

After three months, people in the time-restricted eating group showed improvements in key markers of cardiometabolic health, including blood sugar and LDL cholesterol (bad cholesterol that can clog arteries), as well as lower levels of hemoglobin A1C, a marker of long-term blood sugar control.

The time-restricted eating group experienced a reduction in hemoglobin A1C (HbA1C) levels, from 5.87 to 5.75 percent, compared with a change from 5.86 to 5.84 percent in the standard counseling group.

Although that may sound like a small difference, the decrease in HbA1C is the same amount that was achieved in the Diabetes Prevention Program, which led to a 58 percent decrease in the incidence of type 2 diabetes 2.8 years later, says Manoogian.

People Who Followed Time-Restricted Eating Lost More Weight

Those who followed time-restricted eating also lost an average of about 6.5 pounds (about 3 percent of their body weight) compared with about 3.5 pounds in the control group. According to the food diaries participants kept during the 12 weeks, those who shrank their eating window ate about 350 fewer calories a day.

Time-restricted eaters also reduced their abdominal fat, and overall, they didn't experience significant loss of lean muscle mass.

"It was exciting to see that one lifestyle intervention could improve multiple components of metabolic syndrome. Usually, treatments only impact one aspect of it," says Manoogian.

Time Restricted Eating Could Be a ‘Stealth' Way to Improve Your Eating Habits

These findings suggest you can get additional (although modest) metabolic improvements through time-restricted eating without consciously reducing calories or losing a significant amount of weight, says Adam Collins, PhD , an associate professor of nutrition at the University of Surrey in England, who was not involved in the study.

"The selling point of time-restricted eating is that you are not instructing people to restrict overall intake or food choice, but rather just limiting the eating window," says Dr. Collins.

This study shows that this window can be personalized to fit someone's typical eating and sleeping pattern, which may help the body metabolize meals and how they utilize and store carbs and fat, he says.

Typically people in time-restricted eating trials change their eating habits (even beyond the time window) and people end up eating slightly less, possibly by skipping a meal, avoiding snacking, or by being more mindful of their eating, says Collins.

It often gets people to eat less, more healthfully, or both by "stealth," he adds.

Time-Restricted May ‘Harness the Body's Natural Wisdom'

"Our bodies actually process sugars and fats very differently depending on the time of day," said the co-corresponding author Satchidananda Panda, PhD , a professor and researcher at Salk, in a press release.

Researchers believe that aligning food intake with the body's natural circadian rhythm may enhance how the body metabolizes calories.

"In time-restricted eating, we are re-engaging the body's natural wisdom and harnessing its daily rhythms to restore metabolism and improve health," said Dr. Panda.

Changing When You Eat Instead of What You Eat May Be Easier to Stick With

While the standard recommendation to "eat less and move more" sounds simple enough, it can be difficult to sustain, according to the authors.

The same is true for many popular diets, says Marilyn Tan, MD , an associate professor of medicine and an endocrinologist at Stanford Health Care in California, who was not involved in the study.

"Extremely low carb diets, the keto diet, and other restrictive diets can lead to meaningful weight loss and metabolic improvements in the short term, but many patients find them difficult to sustain long term. The key to success is finding a diet change that one can maintain indefinitely," says Dr. Tan.

People often find it easier to follow time restricted eating rather than very specific macronutrient profiles, she says.

"This study showed benefits at three months, and in a longer-term study, the benefits may be even more notable," says Tan.

"Patients appreciate that they don't have to change what they eat, just when they eat," says Manoogian.

Some People Should Check With Their Doctor Before Trying Time-Restricted Eating

As long as healthcare professionals are aware of the diet plan, there is very little risk to intermittent fasting in itself, says Tan.

"If patients are on insulin or medications that may cause low glucose, then it's important that they discuss the time-restricted eating with their healthcare providers," she says.

Editorial Sources and Fact-Checking

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Sources

1. Manoogian EN et al. Time-Restricted Eating in Adults With Metabolic Syndrome: A Randomized Controlled Trial. Annals of Internal Medicine . September 30, 2024.
2. What Is Metabolic Syndrome? National Heart, Lung, and Blood Institute . May 18, 2022.
3. Diabetes Prevention Program. National Institute of Diabetes and Digestive and Kidney Diseases . August 2021.
4. One in Three Americans Has a Dysfunctional Metabolism, but Intermittent Fasting Could Help. Salk . September 30, 2024.

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Becky Upham

Author

Becky Upham has been professionally involved in health and wellness for almost 20 years. She's been a race director, a recruiter for Team in Training for the Leukemia & Lymphoma Society, a salesperson for a major pharmaceutical company, a blogger for Moogfest, a communications manager for Mission Health, a fitness instructor, and a health coach.

She majored in English at the University of North Carolina and has a master's in English writing from Hollins University.

Upham enjoys teaching cycling classes, running, reading fiction, and making playlists.

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