Food intake also likely plays a role, said Shawn Arent, professor and chair of the exercise science department at the University of South Carolina. He was not affiliated with the study. “You’ve had more waking hours in the day, you’re more awake, you’ve had a chance to fuel the system a little bit more,” Arent said.
Higher body temperatures in the afternoon may also help muscular performance, almost like a built-in daily warm-up.
“When you start to realize how strong this biological clock can be, and then if you do the things like food intake on the wrong time of the day, or being inactive on the wrong time of the day, or being inactive at times when you should be active, this can have a major impact,” Schrauwen added. “The good news is that you can also use it for your benefit.”
Schrauwen said that not snacking in the afternoon and avoiding late-night meals can have a big impact on a person’s weight and overall health. Other studies have shown that late eaters tend to consume more total calories than those who eat earlier in the day.
Arent also said it’s important to eat protein after a workout, but the exact timing of that post-exercise nutrient intake can be flexible — so don’t feel the need to scarf down a shake immediately after a run.