Scientists edge closer to understanding why we gain weight when we eat at night

Now scientists at Northwestern Medicine in Evanston, Illinois say that they have uncovered the workings behind these changes that take place in our bodies. They say their findings have widespread implications when it comes to loss of sleep, diabetes treatment, dieting, and the way that patients who require long-term nutritional help are fed.

Clocks control energy

In explaining their findings, the scientists say that our internal body clock, or circadian rhythm, controls the balance of energy in our bodies by releasing some of that energy at certain times.

The ideal time for the release of this energy is during the hours when daylight is present as a result of the earth’s rotation. At that time, the energy is released from our bodies in the form of heat. That energy fails to be released at times when it is dark. As a result the energy is stored in our bodies and can cause problems such as obesity and diabetes.

Insults lead to insults

Insults to our body clocks will cause insults to the way in which our bodies work, says Dr. Joseph T. Bass, an author of the study and the Charles F. Kettering Professor of Medicine at the Northwestern University Feinberg School of Medicine.

When animals eat our Western-style diets—which are high carb, high fat—their biological clocks become scrambled, he explains.

The circadian clock is sensitive to the times at which people eat, particularly where fat tissue is concerned. That sensitivity, in turn, is disrupted by high-fat diets, Bass adds.

Scientists still do not understand exactly why that happens, but they do know that as animals become obese they begin to eat more when they should be sleeping. The research in this study shows why that is important, he says.

Tests on mice

In the study, mice—who are nocturnal animals and therefore whose body clock is the opposite of that of humans—were fed a diet high in fat. One group of the mice were fed the high-fat diet during their inactive time (daylight) and the other group during their active period (night time).

Within the space of a week, those mice who were fed during the daylight hours gained more weight than those who were fed during the night. The researchers set the temperature in the experimental laboratory to a consistent 30 degrees to lower the effects of temperature on their findings.

The researchers believe that energy balance is involved, says Chelsea Hepler, a postdoctoral fellow in the laboratory run by Bass. That was the reason the mice can eat the same amount of food at different times of the day and yet be healthier when they eat during periods when they are active rather than when they should be sleeping.

Hepler also identified the role of creatine—which helps to maintain energy—in the process. Creatine undergoes release and storage of chemical energy within fat tissues. That indicates that creatine may be the mechanism that underlies the release of heat, she explains.

Internal feeding

The findings can help in cases of chronic care, Bass says, particularly for those patients who receive internal feeding through tubes in their stomachs. These patients commonly are fed during the night when they are asleep. At that time, however, their bodies are releasing the least amount of energy. Rates of obesity and diabetes tend to be high for these patients, Bass says, and the new findings might explain why.

Insulin treatment

Another issue is how the current research findings could affect treatment for Type 2 diabetes. Should meal times be taken into account when patients are given insulin, for example?

Hepler says she will continue to research the role of creatine in the body’s functioning. Researchers need to figure out how the circadian clock controls the body’s functioning involving creatine so we can figure out how to boost it, she says.

Biological clocks are involved a lot in metabolic health when it comes to fat tissue, but scientists are unsure how much yet, Hepler adds.

The study appears in the Journal Science.