PHILADELPHIA — Disrupting sleep-wake cycles from a predominantly daytime to a delayed eating lifestyle, --  i.e., skipping breakfast and making lunch the first meal of the day, plus eating late dinner, disrupts the body’s natural circadian (24-hour) rhythm, the cycle that tells us when to sleep, wake up, eat, and influences hormones and other functions. Penn research has previously shown that delayed eating increases weight, negatively affects fat metabolism, and increases glucose, insulin, triglyceride and cholesterol levels – markers implicated in obesity, heart disease, diabetes and other health problems. Now these researchers have received a grant to figure out why.

Namni Goel, PhD, a research associate professor of psychology in Sleep and Chronobiology, and Kelly Allison, PhD, an associate professor of psychology in Psychiatry, in the Perelman School of Medicine at the University of Pennsylvania, have received a 5-year, $3.75 million grant from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) to continue their research investigating how meal times influence human health.

In their initial research, the team found a daytime eating schedule, compared to a delayed eating schedule, promoted weight loss and a positive profile for fuel oxidation, energy metabolism and hormonal markers in adults of normal weight. This work also showed that short sleep duration increased caloric intake, particularly late at night, leading to weight gain and impaired metabolism. The current study will keep sleep timing and duration constant, only varying the timing of eating, to determine its independent effect on weight and other metabolic measures.

A Centers for Disease Control and Prevention (CDC) report released this month found that 39.8 percent of US adults were obese in 2015-2016. Additionally, the CDC reports that 610,000 people in the United States – one in every four deaths – die of heart disease each year.

“We know from previous research, that the time of day you eat your meals has a significant effect on the body’s weight regulation and other health markers,” said Allison, who also directs the Center for Weight and Eating Disorders. “Now we’re delving deeper into the underlying mechanisms that explain these effects, and how they influence specific populations.”

The five-year NIDDK grant allows the team to conduct a randomized, long-term study of subjects’ eating times to compare weight and metabolic effects and circadian-mediated mechanisms of a daytime versus delayed eating schedule, each of 8 weeks duration, in adults with obesity (BMI of 30-50 kg/m2) without metabolic syndrome (characterized by high blood sugar, high blood pressure, excessive body fat around the waist, and abnormal triglyceride or cholesterol levels). The sleep-wake cycle (hours of the day spent sleeping) and activity levels will be controlled.

“By targeting these mechanisms, we can help in developing treatment of a range of conditions plaguing societies across the globe,” said Goel. “This research has potentially broad clinical implications, including informing recommendations of healthy timed eating habits that influence weight and metabolic health, identifying targets for medical interventions for obesity, and preventing metabolic syndrome and diabetes from developing in persons with obesity.”

Penn Medicine is one of the world’s leading academic medical centers, dedicated to the related missions of medical education, biomedical research, excellence in patient care, and community service. The organization consists of the University of Pennsylvania Health System and Penn’s Raymond and Ruth Perelman School of Medicine, founded in 1765 as the nation’s first medical school.

The Perelman School of Medicine is consistently among the nation's top recipients of funding from the National Institutes of Health, with $550 million awarded in the 2022 fiscal year. Home to a proud history of “firsts” in medicine, Penn Medicine teams have pioneered discoveries and innovations that have shaped modern medicine, including recent breakthroughs such as CAR T cell therapy for cancer and the mRNA technology used in COVID-19 vaccines.

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