Metabolic syndrome affects nearly 30 percent of the U.S. population, and increases the risk for type 2 diabetes, heart disease and stroke. But lifestyle interventions such as adopting a healthy diet and increasing physical exercise are difficult to maintain and, even when combined with medication, are often insufficient to fully manage the disease.

Now, in a collaborative effort, researchers from the Salk Institute and the UC San Diego School of Medicine found that a 10-hour time-restricted eating intervention, when combined with traditional medications, resulted in weight loss, reduced abdominal fat, lower blood pressure and cholesterol, and more stable blood sugar and insulin levels for participants. The pilot study, published in Cell Metabolism on December 5, 2019, could lead to a new treatment option for metabolic syndrome patients who are at risk for developing life-altering and costly medical conditions such as diabetes.

"We have found that combining time-restricted eating with medications can give metabolic syndrome patients the ability to better manage their disease," says Satchidananda Panda, co-corresponding author and professor in Salk's Regulatory Biology Laboratory. "Unlike counting calories, time-restricted eating is a simple dietary intervention to incorporate, and we found that participants were able to keep the eating schedule."

Time-restricted eating (eating all calories within a consistent 10-hour window) supports an individual's circadian rhythms and can maximize health benefits, as evidenced by previous research published by the Salk team. Circadian rhythms are the 24-hour cycles of biological processes that affect nearly every cell in the body. Increasingly, scientists are finding that erratic eating patterns can disrupt this system and increase the risk for metabolic syndrome and other metabolic disorders with such symptoms as increased abdominal fat, abnormal cholesterol or triglycerides, and high blood pressure and blood sugar levels.

"Eating and drinking everything (except water) within a consistent 10-hour window allows your body to rest and restore for 14 hours at night. Your body can also anticipate when you will eat so it can prepare to optimize metabolism," says Emily Manoogian, the paper's co-first author and a postdoctoral fellow in the Panda lab. "We wanted to know if controlling the timing of food intake to support circadian rhythms would improve the health of individuals that were already being treated for cardiometabolic diseases."

"We suspected a 10-hour eating intervention might be beneficial because of Satchidananda Panda's pioneering work in animals, which showed that time-restricted eating led to dramatic health benefits, including a healthier metabolism," adds Michael Wilkinson, co-first author, assistant clinical professor of medicine at UC San Diego School of Medicine and a cardiologist at UC San Diego Health.

The pilot study included 19 participants (13 men and 6 women) diagnosed with metabolic syndrome who self-reported eating during a time window of more than 14 hours per day. Additionally, 84 percent of participants were taking at least one medication such as a statin or an antihypertensive therapy. Study participants used the Panda lab's myCircadianClock app to log when and what they ate during an initial 2-week baseline period followed by the three-month, 10-hour time-restricted eating intervention. Nearly 86 percent of participants correctly logged their food using the app, indicating high compliance throughout the study.

Participants did not report any adverse effects during the intervention. To reduce food intake to the 10-hour window, most participants delayed their first meal and advanced their last meal each day, so meals were not skipped. Although calories were not recommended to be reduced for the intervention, some participants did report eating less, likely due to the shorter eating window.

Overall, participants experienced improved sleep as well as a 3-4 percent reduction in body weight, body mass index, abdominal fat and waist circumference. Major risk factors for heart disease were diminished as participants showed reduced blood pressure and total cholesterol. Blood sugar levels and insulin levels also showed a trend toward improvement.

"Metabolism is closely linked with circadian rhythms, and knowing this, we were able to develop an intervention to help patients with metabolic syndrome without decreasing calories or increasing physical exercise," says Pam Taub, co-corresponding author and associate professor of medicine at the UC San Diego School of Medicine and a cardiologist at UC San Diego Health. "If we can optimize circadian rhythms then we might be able to optimize the metabolic system."

"Adapting this 10-hour time-restricted eating is an easy and cost-effective method for reducing symptoms of metabolic syndrome and improving health," adds Panda. "By delaying the onset of diabetes by even one year in a million people with prediabetes, the intervention could save roughly 9.6 billion dollars in healthcare costs."

The scientists are currently conducting a clinical trial funded by the National Institute of Diabetes and Digestive and Kidney Diseases to examine the benefits of time-restricted eating in a larger group of more than 100 participants with metabolic syndrome. The study includes additional measures that will help the researchers investigate changes in body composition and muscle function.