Roadwork before breakfast: does fasted training do anything?

Running before breakfast is older than any evidence about it. In boxing it is not a training method, it is a piece of the culture, passed down without anybody being asked to justify it.

So the question is worth answering properly rather than dismissing, because the people doing it are not stupid and the practice has outlasted a great many things that argued against it.

The two facts that look contradictory

Both are established, and holding them together is the entire subject.

Nothing about the first is wrong. It just does not lead where people assume.

Fat balance is settled across 24 hours and across a week, not inside a session. Burning more fat at seven in the morning while burning less later in the day nets out. What decides the fat you lose is the deficit across the week, and the state you were in during the run is not a term in that equation.

What about strength work

A different study design, and it arrives in the same place.

A 12-week randomised trial published in 2025 compared resistance training performed fasted against the same programme performed fed. Hypertrophy, strength and power output all improved, and the improvements did not differ between the groups.

Whatever you were worried about losing by lifting on an empty stomach, that trial did not find it. Whatever you were hoping to gain, it did not find that either.

The finding that matters most in a camp

This is the part that changes what I actually advise, and it is not about fat at all.

Sit that inside a fight camp. A fighter is already carrying accumulated fatigue, often already eating less than he would like, and now every session also feels harder than it is. The consequences show up outside the laboratory: in how sessions get judged, in whether the next one is done properly, and in the mood of somebody 6 weeks into a hard block.

The same pattern runs through the wider work on training with low carbohydrate availability. Cell signalling and oxidative adaptations improve in most studies. Actual performance improves in a minority of them.

When it is defensible

Three situations, and none of them is about fat loss.

• Low-intensity work where the intensity genuinely does not matter. An easy morning run, done fasted, costs very little. If it fits your schedule and your stomach, there is no reason to stop.
• Gut training for competition. Rare in this sport, real in others.
• Convenience, and this is the honest one. If training at six in the morning means training fasted, and the alternative is not training, then fasted wins by a distance, because the real comparison is fasted against nothing.

When it is a bad idea

Any session where the intensity is the point. Sparring, hard pads, intervals, anything competitive. Fuelled work performs better in high-intensity efforts, consistently enough to say plainly, and a fighter who spars badly because he did not eat has lost the session rather than gained a metabolic advantage.

Late in a cut. This is where the tradition does the most harm. The fighter is already in a deficit, already low on glycogen, and fasted work stacks a second stressor on a system managing the first.

There is no fat-loss return to justify it, because the deficit is already doing that work.

I would draw that line at roughly the last 3 weeks. That figure is my practical judgment based on how stressors accumulate in late camp rather than a threshold anybody has published, but the direction is not in question.

Where it substitutes for managing intake. A fasted run feels like effort and returns very little, and the hours would give more back spent sleeping or eating properly.

The part about women

There is evidence of a sex difference in fat oxidation during fasted exercise, and the research base in women is thinner than in men.

Given the tighter margins in female weight cutting and the sensitivity of menstrual function to low energy availability, I would not use fasted training as a fat-loss strategy in a female fighter at all. The upside is not established.

The downside is.

What I actually tell people

• If you have always run before breakfast and it suits you, keep doing it. It is not harming you outside a cut, and the habit has value of its own.
• If you are doing it because you believe it burns more fat off you, it does not, and the run would be equally useful with something in you.
• If you are doing it in the closing weeks of a camp, stop. That is the one version where the practice has a real cost and no return.

And if the question underneath this was how to lose more fat, the answer lies in the week the session sits inside, far more than in its timing.