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Time-restricted feeding improves health without altering the body's core clock

When it comes to metabolic health, it's not just what you eat, it's when you eat it.

New ACU research has added to the growing body of evidence showing how time-restricted feeding can improve health even without weight loss.

While previous studies have shown that reducing the number of hours in the day that you eat can be an effective way to lose weight and tackle obesity, the biological explanation for the phenomenon was poorly understood.

Researchers from ACU’s Mary MacKillop Institute for Health Research joined scientists from the University of Copenhagen and the Karolinska Institutet to investigate the body's early adaptations to time-restricted feeding.

Their study, published in Nature Communications, identified several key changes in the genetic ‘signature’ of skeletal muscle, as well as the content of muscle fats and proteins, which could, in part, explain the positive impact of time-restricted feeding.

It is the first study to examine the oscillations of metabolites - molecules that are formed through metabolic processes in skeletal muscle and in blood, as well as gene expression in skeletal muscle after time-restricted feeding.

By focusing on the short-term and early effects of time-restricted feeding, the goal was to unravel the signals that govern health from those associated with weight loss.

Dr Evelyn Parr from the Mary MacKillop Institute for Health Research said the research was an important step towards understanding how time-restricted eating could improve metabolic health, while bridging the gap between animal models and human intervention studies.

“It was important to capture these early metabolic responses before assessing what changes might occur after a longer period following a time-restricted feeding pattern,” Dr Parr said.

In the study, 11 overweight or obese men were assigned one of two eating protocols for a period of five days, either unrestricted feeding (where the duration between the first and last meal of the day was 15 hours), or eight-hours of time restricted feeding.

On the fifth day, muscle and blood samples were taken every four hours for a full day. After a 10-day break, participants repeated the experiment following the other eating protocol.

After each intervention, the team of scientists studied the gene expression in muscles, as well as the profile of metabolites in the blood and muscles.

They found that time-restricted feeding changed the rhythmic concentration of metabolites in blood and muscle. Time-restricted feeding also influenced the rhythmic expression of genes expressed by muscle, particularly those responsible for helping the transport of amino acids, the building blocks of proteins.

Critically, the study showed that time-restricted feeding did not alter the muscle's core clock machinery - the cell's inbuilt metronome that regulates its daily cycle of activity, suggesting that the altered rhythmicity of circulating metabolites and gene expression caused by time-restricted feeding could be responsible for some of the positive health impacts.

"Our findings open new avenues for scientists who are interested in understanding the causal relationship between time-restricted feeding and improved metabolic health says Professor Juleen Zierath from Karolinska Institutet and University of Copenhagen.

“These insights could help develop new therapies to improve the lives of people who live with obesity.”