When it comes to metabolic health, it’s not just what you eat, it’s when you eat it.
Studies have shown that one effective means of losing weight and tackling obesity is to reduce the number of hours in the day that you eat.
Time-restricted feeding—otherwise known as intermittent fasting—has also been shown to improve health even before weight loss kicks in.
The biological explanation for the phenomenon remains poorly understood.
In a new study, researchers examined the body’s early adaptations to time-restricted feeding.
They found a number of key changes in the genetic activity of muscles, as well as the content of muscle fats and proteins, which could explain the positive impact of time-restricted feeding.
The research was conducted by scientists from the University of Copenhagen and elsewhere.
The study is the first time scientists have 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 goal was to disentangle the signals that govern health from those associated with weight loss.
In the study, 11 men with overweight/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 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.
Critically, 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.
This suggests that the altered rhythmicity of metabolite and gene expression caused by time-restricted feeding could be responsible for the positive health impact.
The research is an important step towards understanding how time-restricted eating can improve metabolic health while bridging the gap between animal models and human intervention studies.
These findings open new avenues for scientists who are interested in understanding the causal relationship between time-restricted feeding and improved metabolic health.
One author of the study is Postdoc Leonidas Lundell.
The study is published in Nature Communications.
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