Intermittent fasting didn’t reduce belly fat in mice

Not all fat is the same, and some of it doesn’t like going hungry.

Intermittent fasting, where you restrict your food intake every other day, has been popular for a few years now, but a new study suggests it might not give everyone the results they’re looking for.

Australian researchers led by Dr. Mark Larance mapped out what happens to fat deposits during this type of intermittent fasting, with an unexpected discovery that some types of fat are more resistant to weight loss.

The University of Sydney team found that fat around the stomach, called visceral fat, which can accumulate into a “protruding tummy” in humans, was found to go into “preservation mode,” adapting over time and becoming more resistant to weight loss.

Changes were also seen in subcutaneous fat, which lies just under the skin and is associated with better metabolic health.

“While most people would think that all fat tissue is the same, in fact, the location makes a big difference,” said Larance, from the Charles Perkins Centre and School of Life and Environmental Sciences at the University of Sydney.

“Our data show both visceral and subcutaneous fat undergo dramatic changes during intermittent fasting,” Larance added.

Fat tissue provides energy during fasting by releasing fatty acid molecules. The researchers, however, found visceral fat became resistant to this release.

There were also signs that visceral and subcutaneous fat increased their ability to store energy as fat, likely to rapidly rebuild fat stores before the next fasting period.

According to Larance, it’s possible a history of repeated fasting triggers visceral fat to preserve.

“This suggests the visceral fat can adapt to repeated fasting bouts and protect its energy store,” he said. “This type of adaptation may be the reason why visceral fat can be resistant to weight loss after long periods of dieting.”

The research was done on mice because “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,” Larance said.

He added the findings may not apply to the 5:2 diet (fasting two days out of seven) or calorie restriction, which is common in people trying to lose weight.

The findings were published Wednesday in the journal Cell Reports.