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Penn Researchers to Study How Mealtimes Influence Human Health

Disrupting sleep-wake cycles from a predominantly daytime to a delayed eating lifestyle—ie, 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 in Philadelphia, have received a five-year, $3.75 million grant from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) to continue their research investigating how mealtimes influence human health.

In their initial research, the team found a daytime eating schedule, compared with 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%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," says 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 vs delayed eating schedule, each of eight 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," Goel says. "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."