Eating late dinners can disrupt the biological clock that determines a person's daily circadian rhythm, leading to obesity and diabetes, according to a Waseda University research team.
The team is led by Prof. Shigenobu Shibata, who specializes in pharmaceutical science.
Its findings were based on experiments with mice.
It had been known that disruption of the internal body clock can cause obesity and diabetes, but Shibata's team discovered the mechanism behind these problems, Shibata said.
The biological clock of living things is controlled by "clock genes" in cells. The internal body clock controls functions such as sleep, wakefulness, body temperature and hormonal secretion on a cycle that is about 24 hours long.
Although a day consists of 24 hours, the biological cycle varies somewhat depending on the species. The human cycle is about 24-1/2 hours while that of mice is between about 23-1/2 and 24 hours.
People's circadian rhythm is adjusted by daylight and the intervals between meals.
The researchers examined the rhythm of body clocks by feeding mice three times a day on different schedules and measuring the functions of clock genes in their kidneys and livers.
They found that mice's body clocks were properly reset to begin a new daily cycle when breakfast was eaten after a relatively long interval since the last meal of the previous day. The feeding schedule that seemed to work best was 7 a.m., noon and 7 p.m.
Feeding the mice the last meal of the day at 10 p.m. threw their body clocks out of sync by two or three hours, the team found.
The researchers concluded that the rhythm of body clock becomes the most disrupted as the intervals between lunch and dinner and between dinner and breakfast become almost the same.
When the mice's last meal of the day was divided into two eatings, one at 7 p.m. and the other at 10 p.m., the disruption of their circadian rhythm was was limited to between 1-1/2 and two hours, the team found.
"Regular eating habits will help prevent obesity," Shibata said.