April 22, 2005
The Sleep-Wake Body Clock May Also Control Appetite
Study offers possible clue to overeating in humans
HealthDay News -- Our molecular body clock may also play a role in regulating appetite, researchers report, in a finding that could someday be used to help compulsive eaters slim down.
Mice bred to have irregular body clocks were unable to keep their body weight under control, said the report in the April 21 online issue of Science by investigators at Northwestern University.
"These animals have the munchies all day long and in actuality eat all night long as well," said lead investigator Dr. Joseph Bass, an assistant professor of medicine, neurobiology and physiology at Northwestern. Mice with normal body clocks eat just twice a day, he added.
The finding offers no immediate solution to the human problem of obesity, and related health problems such as diabetes, Bass said. But it does add to "the abundant evidence that timing is important" in eating habits, he said. "It will be a matter of time before we know how to translate this into practical advice [for people], but it makes us aware of how important synchronization is to eating."
One important finding is that "the clock, which we thought is only in the central part of the brain, actually is also present in the part of the brain that controls appetite," Bass said.
Biological clocks function not only in the brain but in many parts of the body as well. They govern not only the sleep cycle but also functions including fluid balance, body temperature, oxygen consumption -- and now, it has been shown, appetite, the researchers said.
"This provides new genetic evidence that physiological outputs of the biological clock, sleep and appetite are interconnected at the molecular and behavioral levels," said Fred W. Turek, professor of neurobiology and physiology at Northwestern, and a member of the research team.
The finding could help develop new strategies "to reduce and sustain weight loss resulting from both medical and lifestyle modifications," Turek said.
There already is a lot of evidence that when people ignore the signals of their body clock and deprive themselves of sleep -- for example, the student who crams all night before an exam or the worker on a night shift -- they can develop medical problems, Bass said.
"We provide some molecular explanation that might account for the health problems that humans induce through their deliberate misalignment of the clock," he said.
The test mice were unable to control their weight when fed an ordinary diet or one rich in fats. Those fed an ordinary diet had weight gains comparable to the kind seen in normal mice on a high-fat diet. The genetically altered mice fed a high-fat diet had abnormalities in insulin secretion and in the ability of the liver to handle sugar -- the kind of problems seen in humans with diabetes, the researchers said.
"If we take our work in the context of studies in humans, we might at least begin to think about the question of timing as it pertains to food consumption," Bass said.
The basics of body clocks are explained by the National Institute of Mental Health.