Fuelling the Lunch Break Workout: What to Eat Before and After a 45-Minute Session

Forty-five minutes is enough to do something meaningful. It is not enough to waste time figuring out nutrition.

The lunch break workout is one of the most valuable tools a time-crunched triathlete has. A 45-minute brick, a threshold run, a quality swim — done consistently over months, these sessions add up to a significant portion of your total training volume. But they only work if you fuel them correctly. Turn up under-fuelled and you'll have a mediocre session and spend the afternoon in a mental fog. Over-fuel and you'll spend the first ten minutes regretting breakfast.

Here's the framework.

Before: what you're actually trying to do

You're not trying to fuel the session from a pre-workout meal. You're trying not to arrive at the session so depleted that performance tanks.

If you ate breakfast two to three hours earlier and it contained a reasonable amount of carbohydrate, you're probably fine. You don't need a specific pre-workout meal for a 45-minute session. Your glycogen stores from breakfast will carry you.

The exception is if breakfast was light or you ate it more than four hours ago. In that case, 30–45 minutes before training, have something small and carbohydrate-forward: a banana, a piece of toast, a small handful of dried fruit. Enough to raise blood glucose slightly without putting anything heavy in your stomach.

What to avoid: high-fat, high-protein foods in the hour before training. They slow gastric emptying, meaning they're still sitting in your stomach when you're trying to run. Avoid fibre for the same reason if your session is run or brick-based.

During: almost certainly nothing

For a 45-minute session, you don't need to eat anything. Your glycogen stores are sufficient. If you feel the urge to take a gel mid-session, it's almost certainly psychological rather than physiological — athletes who habitually use gels start to feel like they need them even when they don't.

The one exception is if your session is particularly intense — sustained threshold work with minimal recovery — and you haven't eaten for four or more hours before. In that case, 20g of carbohydrate (roughly half a gel) around the 30-minute mark won't hurt. But this is the edge case, not the default.

Hydration is different. Drink water before and during, especially in warm conditions. A 45-minute session in the heat can produce meaningful dehydration. This matters more than calories.

After: the window that actually matters

This is where most lunch-break athletes under-invest. You finish the session, shower, rush back to your desk, and eat whatever's convenient three hours later. The recovery opportunity is gone.

The 30–60 minutes after a session is when your muscles are most receptive to glycogen replenishment and protein synthesis. This isn't sports science mythology — it's well-established physiology. Miss this window and your recovery is slower, your next session is harder, and your adaptation over time is reduced.

The target after a 45-minute quality session: 30–40g of carbohydrate, 20–25g of protein, within an hour of finishing.

This doesn't need to be elaborate. Greek yoghurt with a banana hits both. A chicken or tuna sandwich on wholegrain bread is close. A protein shake with a piece of fruit if you're on the go. The specifics matter less than the timing and the rough macronutrient targets.

The practical reality

The biggest barrier isn't knowing what to eat — it's having it ready. Pack your post-workout food the night before. Treat it with the same planning as your kit bag. Athletes who arrive at their lunch break workout without a recovery meal already sorted consistently skip it, and the compounding cost of that over a training cycle is significant.

One other thing: eat a real lunch. The lunch break workout is not a reason to skip the meal. If you trained at 12:30 and had your recovery snack by 1:30, eat lunch at 2pm. Chronic under-eating during heavy training weeks is one of the fastest routes to overreaching and fatigue.

Forty-five minutes in. Fuelled well. Back at your desk by 2pm and actually able to think.

That's the goal.