Studies in mice show type of fat influences fasting effectiveness

Researchers from the University of Sydney mapped out what happens in fat tissue during intermittent fasting, showing that it triggers a cascade of dramatic changes, depending on the type of fat deposits and where they are located around the body, according to a new mouse study published in the journal Cell Reports.

The study was conducted using the instruments at the Sydney Mass Spectrometry in the Charles Perkins Centre, part of the University of Sydney's Core Research Facilities. For the study, researchers examined fat tissue types from different locations to understand their role during every-other-day fasting, where no food was consumed on alternate days. The fat types where changes were found included visceral 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. 

During fasting, fat tissue provides energy to the rest of the body by releasing fatty acid molecules, the researchers said. However, the researchers said they 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, according to the study.

The research team examined more than 8,500 proteins located in fat deposits, creating a catalogue of changes that occurred during intermittent fasting, using a technique called proteomics. Proteomics or the study of all proteins is a relatively new area of study that takes its name from genomics, the study of all genes, and monitors how proteins react under certain conditions, in this case intermittent fasting.

The results provide a rich source of data that helps to paint a more complete picture of the inner workings of fat tissue. It was via proteomics that the research team were alerted of major cellular changes caused by intermittent fasting and, after further analysis, highlighted the visceral fat's preservation mechanism in action.

The researchers note that findings from the intermittent study may not apply to different diet regimes such as the 5:2 diet, fasting two days out of seven, or calorie restriction, which is common in people wanting to lose weight.

Future research in mice and humans could uncover the mechanisms by which this resistance occurs, as well as also which types of diet and other interventions may be best at tackling belly fat, the researchers said. The results lay the foundation for future studies, which will dissect the molecules responsible for why visceral fat is resistant to energy release during fasting and help determine what diet plans would be most beneficial for metabolic health.

"This sort of research has been enabled by these new instruments that allow us to look beyond the streetlight,” said Mark Larance, PhD, senior author of the study, in a statement. “We knew we would find something, but we didn't know what.  Now that we've shown belly fat in mice is resistant to this diet, the big question will be to answer why, and how do we best tackle it?"