Endurance running requires a specific type of muscle fibres
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Shifting your mealtimes to eat later in the day and during the night could boost your exercise endurance, suggests a study in mice.
Limiting your eating to within windows of six to 12 hours during daytime, without necessarily altering what or how much you eat, has been previously found to improve weight loss, reduce harmful spikes in blood sugar levels and lower blood pressure. But now it seems night-time eating could also offer benefits, says Min-Dian Li at the Army Medical University in China.
Earlier studies have shown that mice that eat only in the day – when, unlike us, they usually rest – are at greater risk of developing diabetes and a build-up of fat in their livers compared with mice that eat at any time. There is also evidence that people who work and eat at nights have increased risk of diabetes.
But Li and his colleagues have now found that mice that eat during their resting hours, the equivalent of our night, may perform better in exercise endurance tests. “If we treat the mice with this schedule for just a short time it has a beneficial effect on running performance,” he says.
The researchers assigned 30 mice to feed on a diet of cereal grains in either a 12-hour period when lights were on or a 12-hour period when lights were off, each day for three weeks. Another group of 16 mice were allowed to eat whenever they wanted over the same time period.
Using a treadmill, the team found that mice that only ate in the day could run for twice as long compared with mice that only ate in the night or whenever they wanted.
Analysing the leg muscles of mice revealed that those fed in the daytime had more of a type of muscle fibre used in endurance running than the others, helping to explain the differences seen, says Li.
Further analysis of muscle samples extracted from the mice revealed that daytime eating was linked with lower levels of a protein called perilipin-5. To test whether this might account for the higher endurance, the team genetically edited another set of mice to lack this protein in their muscles and allowed them to eat when they liked. Putting these mice through the treadmill test and analysing their muscles revealed that lower perilipin-5 levels were indeed responsible for the effects of daytime-only feeding on running endurance in mice.
“As mice are nocturnal, the equivalent treatment in humans could be to eat in the night, or perhaps eat less earlier in the day and have a big dinner just before you sleep,” says Li, though this still has to be tested in humans, he says.
The researchers didn’t measure the effect this rest-time eating had on the mice’s risk of diabetes or fatty livers, though in future Li says they plan to look at the impact on organs beyond skeletal muscles. If people adopt night-time eating as a temporary measure – before a big race, say – they may not experience the negative effects seen by people who do so in the long-term, but ultimately further testing is needed, says Li.
“It’s important to stress that this might work by switching your eating schedule for just a few months – the human equivalent of three weeks in mice – or a short period, rather than for a longer timeframe, running up to when you need an endurance boost,” he says.
What’s more, “adjusting mealtimes in this way could potentially help treat ageing in people who could benefit from greater muscle endurance”, says Li.
“While the results are exciting, they need to be confirmed in humans,” says Juleen Zierath at the Karolinska Institute in Sweden. One limitation of the study is that the mice ate a cereal-based diet which is “not at all the kind of diet that humans typically eat”, she says, meaning more varied meals might have a different effect.
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