28-06-2025
Study: Inactivity, no breakfast tied to abdominal obesity in rats
Skipping breakfast and physical inactivity may lead to the potbellies that are common among middle-aged men, researchers have found through an experiment utilizing rats as the test subjects.
A research team led by professor Hiroaki Oda of Nagoya Bunri University conducted an experiment to see how skipping breakfast would affect physically inactive rats fed with a high-fat diet.
Specifically, 29 male rats whose sciatic nerves were cut to reduce their amount of activity by half were fed with a diet containing the average percentage of fat consumed by Americans for 11 days.
Rats are a nocturnal animal that is active during the night and rests during the day, so their sleep-wake cycle is opposite of humans.
In this case, the beginning of their active period was deemed "morning."
The rats were divided into two groups: a breakfast-skipping group of 15 rats that were given no food for four hours after the day's start; and another group of 14 rats that were allowed to eat any time during the active period.
Both groups ate the same amount of food.
The researchers found that while there was no difference in weight gain between the two groups, the breakfast-skipping group only gained visceral fat.
"It is possible that their biological clock was disrupted by skipping breakfast, and, as a result, their metabolism was also disrupted and they accumulated visceral fat," Oda said. "There is a possibility that we can prevent abdominal obesity and metabolic syndrome when we move enough in everyday life, have breakfast and eat regularly at appropriate intervals."
Obesity is divided into two categories: subcutaneous obesity, which is induced by fat accumulation under the skin; and visceral obesity resulting from fat accumulation around the abdominal area.
The latter is also known as abdominal obesity, or a potbelly, which is said to contribute to lifestyle-related diseases caused by harmful substances from fat cells.
It was long thought that excessive fat intake and overeating would cause abdominal obesity.
But even though the test animals were fed with a high-fat diet, they only gained overall body fat.
The mechanism of why fat accumulates only in the abdomen had remained unknown.
And while it is known that physical inactivity and irregular eating habits are unhealthy, however, it wasn't clear how human's health would be impacted by these two factors when they were combined.
Specializing in chrononutrition, Oda has been studying not only what but also when people eat can contribute to good health.
His previous projects using experimental animals showed that skipping breakfast can lead to muscle loss and that grazing, which is characterized as eating small amounts all day long, increases blood cholesterol levels.
"In these times when we can get sufficient nutrients, I think that it is when we eat rather than what we eat that actually affects our health," Oda said.
The team's findings were published online in the journal Scientific Reports (
