More uncovered on link between late-night eating and weight gain, diabetes

Scientists have uncovered details of the metabolism of late-night eating associated with weight gain and diabetes, according to a study.

While the connection between time, sleep and obesity is well-known, it is misunderstood because research showed that overnutrition can disrupt circadian rhythms and change fat tissue, the study by a team of researchers from the Northwestern University stated.

It also showed that energy release may be the molecular mechanism through which the internal clocks of human beings control energy balance.

From this understanding, the scientists also found 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, published in the journal Science, have broad implications from dieting to sleep loss and the way patients who require long-term nutritional assistance are fed.

"It is well known, albeit poorly understood, that insults to the body clock are going to be insults to metabolism," said study author Dr. Joseph T Bass.

"When animals consume Western style cafeteria diets high fat, high carb the clock gets scrambled," he 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," Bass said.

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, according to a statement.

The challenge for Bass' 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, the scientists said in the statement.

In the study, mice, who are nocturnal, were fed a high-fat diet either exclusively during their inactive (light) period or during their active (dark) period. Within a week, mice fed during light hours gained more weight compared to those fed in the dark.

The team also set the temperature where mice expend the least energy. This was done to mitigate the effects of temperature on their findings.

"We thought maybe there's a component of energy balance where mice are expending more energy eating at specific times," said Chelsea Hepler, co-author of the study.

"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 the energy expenditure led the team to look into 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.