Every few years, “fasted exercise” makes a comeback on social media – the idea that training before breakfast is the ultimate fat-burning hack.

Supporters claim it’s the fastest route to weight loss. Critics argue it’s counterproductive. So, who’s right? Research shows that exercising on an empty stomach does increase fat burning during the workout.

However, long-term studies, including a 2017 review, find it doesn’t translate into greater fat loss overall. That’s because the body tends to balance things out later in the day.

For performance, eating beforehand matters more for endurance workouts lasting over an hour. For shorter or strength-based sessions, the evidence suggests little to no difference whether you’ve eaten or not.

Potential downsides? Some people feel hungry, dizzy, or nauseous when exercising fasted – while others swear by the energy boost.

The takeaway: fasted training isn’t a magic bullet for fat loss or performance, but it’s not harmful for most people either. If skipping breakfast helps you fit in a workout, go for it. If it makes exercise miserable, eat first.

The one constant that matters most? Exercising regularly – no matter when, no matter how.