Scientists have uncovered the mechanism behind why eating late at night is linked to weight gain and diabetes.
The connection between eating time, sleep and obesity is well-known but poorly understood, with research showing that over-nutrition can disrupt circadian rhythms and change fat tissue. The new northwest research has shown for the first time that energy release may be the molecular mechanism through which our internal clocks control energy balance.
Scientists have also discovered that daytime is the ideal time in the light environment of the Earth’s rotation when it is most optimal to dissipate energy as heat. These findings have broad implications, from dieting to sleep loss and the way we feed patients who require long-term nutritional assistance. The paper, “Time-restricted feeding mitigates obesity through adipocyte thermogenesis,” will be published online today. “It is well known, albeit poorly understood, that insults to the body clock are going to be insults to metabolism,” said the corresponding study author, Dr. Joseph T. Bass, the Charles F. Kettering Professor of Medicine at Northwestern University Feinberg School of Medicine. He is also a Northwestern Medicine endocrinologist.
“When animals consume Western-style cafeteria diets—high fat, high carbohydrate—the clock gets scrambled,” Bass said. “The clock is sensitive to the time people eat, especially in fat tissue, and that sensitivity is thrown off by high-fat diets. We still don’t understand why that is, but what we do know is that as animals become obese, they start to eat more when they should be asleep. This research shows why that matters”
Chelsea Hepler, a postdoctoral fellow in the Bass Lab, said, “That’s why they can eat the same amount of food at different times of the day and be healthier when they eat during active periods versus when they should be sleeping.” The increase in energy expenditure led the team to look into the metabolism of fat tissue to see if the same effect occurred within the endocrine organ. They found that it did, and mice with genetically enhanced thermogenesis — or heat release through fat cells — prevented weight gain and improved health. Hepler also identified futile creatine cycling, in which creatine (a molecule that helps maintain energy) undergoes storage and release of chemical energy, within fat tissues, implying creatine may be the mechanism underlying heat release.
The science is underpinned by research done by Bass and colleagues at Northwestern more than 20 years ago that found a relationship between the internal molecular clock and body weight, obesity, and metabolism in animals. The challenge for Bass’s lab, which focuses on using genetic approaches to study physiology, has been figuring out what it all means and finding the control mechanisms that produce the relationship. This study brings them a step closer.