In a joint study on time-restricted eating, the UC San Diego School of Medicine and Salk Institute found that limiting food consumption to a 10-hour window each day, within one hour after waking up to three hours before sleeping, improves the cardiometabolic health of patients with metabolic syndrome. The TIMET clinical trials were funded by the National Institute of Diabetes and Digestive and Kidney Diseases and recently featured in an issue of Annals of Internal Medicine on Sept. 30.
Metabolic syndrome is a diagnosis categorized by having three or more of a variety of medical conditions that can lead to heart disease and diabetes. The medical conditions include increased glucose levels, blood pressure, cholesterol, waist circumference, and triglycerides, a type of lipid found in blood.
Michael Wilkinson, an author of the study and associate professor of medicine in the Division of Cardiovascular Medicine at UCSD, spoke to The Guardian.
“Our hypothesis for this study was that when people eat over a long period of time each day, so if you’re waking up early and having something to eat or having dinner late, you’re exposing the body to nutrient intake and calories outside of the body’s circadian metabolism,” Wilkinson said.
A circadian rhythm is the body’s internal clock. It controls many of the biologic functions that occur in a day, including metabolism.
“When people eat in the middle of the day, their bodies are already primed to handle that dietary intake and metabolize it efficiently. But if you’re eating late into the night, your circadian clock is telling your metabolism ‘you’re supposed to be stopping now,’ but we ignore that, and we just keep eating into the night.”
When one is continuously consuming food throughout the day, the body’s circadian rhythms are disrupted, so one’s metabolism can not function properly, “specifically the way that the body handles dietary intake and blood sugar.”
Satchidananda Panda, co-corresponding author of the study and professor at the Salk Institute, spoke to UC San Diego Today about the link between TRE and the body’s ability to regulate natural processes through circadian rhythms.
“In time-restricted eating, we are re-engaging the body’s natural wisdom and harnessing its daily circadian rhythms to restore metabolism and improve health,” Panda said.
Participants in the experimental group displayed significant improvements in glucose and cholesterol levels after completing TRE for three months. Lower hemoglobin A1C test results were also observed. This test assesses the average blood sugar of a patient over a three-month period and their possibility of being diagnosed with prediabetes or type 2 diabetes.
Low test results attributed to TRE demonstrate how intermittent fasting can reduce a patient’s risk of developing metabolic diseases.
The Guardian inquired about some of the study’s potential limitations including patients’ diets and exercise. In response, Wilkinson explained how a 24-hour diet recall conducted by a study dietitian and the use of movement-monitoring devices were used to assess any major changes in calorie intake from the beginning and end of the study.
“We have data from wrist-worn actigraphy devices that we used at the beginning and end of the study to make sure there hasn’t been any major change in physical activity that might impact our findings,” he said. “There weren’t data on the devices to suggest that what we were seeing was clearly influenced by any change in activity levels over the course of the study.”
The university’s efforts on testing the impact of TRE on metabolic health are ongoing.
“We’ve been fortunate to collaborate with our co-investigators at the Salk Institute on other clinical trials in time restricted eating at UCSD,” Wilkinson said.
