A 2025 study on fat oxidation rates and exercise timing is getting more press on social media this week. Because why not… 🙂 Here’s the deal:
In a study of (yes, you guessed it) male college students, researchers found that 60 minutes of morning exercise before breakfast, after fasting all night, resulted in 20% higher fat oxidation rates than an hour of the same exercise after eating dinner.
Uh, yay?
Actually, I think the more appropriate reaction here is: meh.
Why am I not excited about this? I mean, it’s SCIENCE.
Yes, that’s so. It’s real science done by real scientists, on real experimental young male subjects. And, this is a real result. But, it doesn’t mean that we should all switch to exercising before breakfast. Why not? Here are some concerns of mine, plus some by the commenters:
- The purpose of exercise is not necessarily to lose fat– we exercise for a host of reasons, and possible fat reduction is only one of them.
- Fat oxidation does equal fat loss. In order to lose fat, there has to be a calorie deficit in addition to fat oxidation.
- Some commenters argued that the results are largely due to the fact that the subjects had fasted before exercise; there’s no indication in the study that the time of day mattered (other than it’s easier to fast while sleeping– I don’t actually need a scientific study to assert this with confidence).
- The metabolic effects on a busload of twenty-something males are not necessarily applicable to the larger population. And in particular, we know that metabolic effects of exercise vary by gender, so this result may not apply in the same way to everyone.
However, my main point is: newsy stories about studies that suggest “you oughta exercise like THIS rather than like THAT” ignore the value of just getting out there– to your neighborhood, living room, gym, yoga studio, pond, wherever you like to be while moving. Feel free to move wherever and whenever suits you.
And while we’re at it, moving before breakfast is something I plan on doing only if a bear is chasing me. Or if one of my friends (Samantha and Janet, I’m looking at y’all) manages to talk me into a very early-morning adventure. But even then, I’ll need snacks.
