Fasting every second day appears to cause the fat around the stomach and other organs – the kind that makes a protruding belly – to stay put.
This is called visceral fat – and it’s designed to be burnt off quickly as energy when food runs short, as a survival mechanism.
But if fasting continues, visceral fat digs in and resists being burnt off.
This was the surprising finding when University of Sydney researchers mapped out “what happens behind the scenes in fat tissue during intermittent fasting”.
The study was conducted with mice from the University of Sydney.
Senior author Dr Mark Larance, from the Charles Perkins Centre and School of Life and Environmental Sciences, said:
“Mouse physiology is similar to humans, but their metabolism is much faster, allowing us to observe changes more rapidly than in human trials, and examine tissues difficult to sample in humans,” he said, in a prepared statement.
Responding to questions by email, he added:
“Using our findings in mice, we can now run a hypothesis-driven experiment to find out this occurs in human participants.”
What previous research found
Previous research in both rodents and humans found that intermittent fasting has been demonstrated to reduce insulin levels, improve glucose tolerance, and lower blood cholesterol.
Intermittent fasting is done in a number of ways. Some people restrict to an eight-hour period (or less) each day. Others take the 5-2 route, where regular eating occurs over five days, and greatly reduced over two days.
Or, you can eat one day, fast the next – meaning you eat nothing. This is known as every-other-day fasting. Which was the diet the Sydney mice were on.
How did the researchers make their discovery?
According to a statement from the University of Sydney:
- There are different types of fat in the body, including visceral “belly” fat, which is fat tissue surrounding our organs including the stomach, and subcutaneous fat, which lies just under the skin and is associated with better metabolic health.
- Using mass spectrometry, the research team examined more than 8500 proteins located in fat deposits, creating a catalogue of changes that occurred during intermittent fasting.
- This is a new area of study called proteomics.
- During fasting, fat tissue provides energy to the rest of the body by releasing fatty acid molecules.
- However, the researchers found visceral fat became resistant to this release of fatty acids during fasting.
- There were also signs that visceral and subcutaneous fat increased their ability to store energy as fat, likely to rapidly rebuild the fat store before the next fasting period
“While most people would think that all fat tissue is the same, in fact, the location makes a big difference,” said Dr Larance.
It was possible, he said, that a history of repeated fasting periods “triggered a preservation signalling pathway” in visceral fat.
“This suggests the visceral fat can adapt to repeated fasting bouts and protect its energy store,” he said.
See here for advice from Harvard University on how to reduce belly fat.