Time-restricted feeding improves health without altering body clock

Time-restricted feeding or intermittent fasting causes several changes in the genetic activity of muscles, which could explain its positive impact, according to new research study by the University of Copenhagen, the Australian Catholic University, and Karolinska Institutet published in the journal Nature Communications.

For the study, researchers examined the oscillations of metabolites 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 researchers said the goal was to disentangle the signals that govern health from those associated with weight loss.

In the study, 11 men with overweight or obesity were assigned one of two eating protocols for a period of five days, either unrestricted feeding, or eight-hours of time restricted feeding. On the fifth day, samples were taken every four hours for a full day. After a 10-day break, they 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, molecules that are formed through metabolic processes, in the blood and muscles.

They discovered 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, according to the study.

The researchers also said the study showed that time-restricted feeding did not alter the muscle's core clock, the cell's inbuilt metronome that regulates its daily cycle of activity. The researchers said this suggests that the altered rhythmicity of metabolite and gene expression caused by time-restricted feeding could be responsible for the positive health impact.

"Our findings open new avenues for scientists who are interested in understanding the causal relationship between time-restricted feeding and improved metabolic health,” Juleen Zierath, PhD, corresponding author of the study and professor at the Karolinska Institutet, in a statement. “These insights could help develop new therapies to improve the lives of people who live with obesity.”