Emily Manoogian and Satchin Panda Credit Salk Institute

Approximately one-third of adults in the United States have metabolic syndrome, a group of conditions that greatly increase a person’s risk of heart disease, stroke, and type 2 diabetes. These conditions consist of high blood pressure, elevated blood sugar, excess abdominal fat, and abnormal cholesterol levels.

In a recent clinical trial, researchers at the Salk Institute and the University of California San Diego School of Medicine discovered that time-restricted eating, also known as intermittent fasting, could provide significant health benefits to adults with metabolic syndrome. Patients who adhered to a consistent eight-to-ten-hour eating window each day for three months experienced improvements in various markers of blood sugar regulation and metabolic function compared to those who received standard treatments.

“Our bodies process sugars and fats very differently depending on the time of day,” says Salk Professor Satchidananda Panda, co-corresponding study author and holder of the Rita and Richard Atkinson Chair. “In time-restricted eating, we are re-engaging the body’s natural wisdom and harnessing its daily rhythms to restore metabolism and improve health.”

“For many patients, metabolic syndrome is the tipping point that leads to serious and chronic diseases such as diabetes and heart disease,” says co-corresponding author Pam Taub, who is a professor of medicine at the UC San Diego School of Medicine and a cardiologist at UC San Diego Health. “There is an urgent need for more effective lifestyle interventions that are accessible, affordable, and sustainable for the average American.”

Western diets high in sugar, salt, and fat, combined with increasingly sedentary lifestyles, are believed to have led to increasing rates of metabolic dysfunction. While the initial recommendation may be to “eat less and move more,” these lifestyle changes are challenging for most people to maintain long-term. Researchers suggest that time-restricted eating provides a more practical approach that is accessible to a wider range of patients, including those already on medication.

“Unlike expensive pharmaceuticals like Ozempic, which require lifetime use, time-restricted eating is a simple lifestyle change that doesn’t cause side effects and can be maintained indefinitely,” says first author Emily Manoogian, a staff scientist in Panda’s lab at Salk. “Patients appreciate that they don’t have to change what they eat, just when they eat.”

The new study customised time-restricted eating protocols to each participant’s eating habits, sleep/wake schedules, and personal commitments. The resulting regimen had them reduce their eating window to a consistent eight to ten hours per day, beginning at least one hour after waking up and ending at least three hours before going to sleep. Manoogian says this personalized approach made the intervention easier for patients to complete, compared to other intermittent fasting studies, which typically assign the same strict time window to all participants.

The TIMET study also accepted participants who were on medication for metabolic syndrome—a group usually excluded from such trials. This makes it the first study to measure the benefits of time-restricted eating in addition to existing standard-of-care pharmacological treatments. 

The study randomly sorted 108 adults with metabolic syndrome into either the time-restricted eating group or the control group. Both groups continued to receive standard-of-care treatments and underwent nutritional counselling on the Mediterranean diet. Participants also logged their meals using the myCircadianClock mobile app, developed at Salk. 

After three months, patients who had completed the time-restricted eating regimen showed improvements in key markers of cardiometabolic health, including blood sugar and cholesterol. They also saw lower levels of haemoglobin A1c, a marker of long-term blood sugar control. This reduction was similar in scale to what is typically achieved through more intensive interventions by the National Diabetes Prevention Program. 

The time-restricted eating group also showed 3-4% greater decreases in body weight, body mass index (BMI), and abdominal trunk fat, which is closely linked to metabolic disease. Importantly, these participants did not experience significant loss of lean muscle mass, which is often a concern with weight loss.