High-Intensity Interval Training demands explosive energy. You'll be pushing maximum effort in short bursts, repeatedly. What you eat beforehand determines whether you hit those intervals hard or fade halfway through.
HIIT is unique because it relies heavily on carbohydrates for fuel. Unlike steady-state cardio where your body can tap into fat stores, high-intensity efforts burn through glycogen rapidly. Your pre-workout nutrition needs to match this energy demand.
Why HIIT Nutrition Is Different
During HIIT, you're repeatedly pushing into anaerobic territory. This means:
- Carbohydrates are essential: Anaerobic exercise primarily burns glucose, not fat
- Blood glucose matters: Low blood sugar = early fatigue and poor performance
- Digestion time is limited: Most HIIT sessions are 20-45 minutes - no time for mid-workout fuel
- Intensity affects digestion: High-intensity work diverts blood from stomach to muscles
Carbohydrate availability directly impacts high-intensity exercise performance. Glycogen is your body's primary fuel source during exercise lasting more than a few minutes, and starting with higher glycogen levels leads to greater power output.
The impact is dramatic: during high-intensity exercise with reduced muscle glycogen, consuming carbohydrates extends time-to-exhaustion from 2.5 minutes to 7.1 minutes - nearly three times longer.
Pre-HIIT Timing Strategy
Aim for 1-4g carbohydrate per kg bodyweight in the 1-4 hours before exercise. For a 70kg person, that's 70-280g carbs. A meal of chicken, rice, and vegetables fits well here.
200-300 calories, predominantly carbohydrate with moderate protein. Porridge with banana, toast with peanut butter, or a small pasta portion.
100-200 calories of easily digestible carbs - banana, dates, rice cakes, or a sports drink. Keep fibre and fat minimal to avoid GI issues.
If you can't eat 2+ hours before, a small carb snack 20-30 minutes before still helps. Alternatively, eat a carb-rich dinner the night before to maximise overnight glycogen stores.
Best Foods Before HIIT
2-3 Hours Before
Chicken & Rice
Balanced meal with slow-release carbs and lean protein. Classic pre-workout option.
Pasta with Tomato Sauce
Carb-rich for glycogen, easy to digest. Keep protein moderate and fat low.
Toast with Eggs
Good breakfast option for afternoon HIIT. Carbs from toast, protein from eggs.
Porridge with Banana
Sustained energy release. The banana adds quick carbs and potassium.
60-90 Minutes Before
Banana & Peanut Butter
Quick carbs, some protein, easy to eat. Popular for good reason.
Greek Yoghurt with Berries
Protein plus carbs, easy on the stomach. Add honey for extra energy.
Rice Cakes with Jam
Very light, fast-digesting carbs. Good if you struggle with pre-workout eating.
Small Bowl of Cereal
Quick energy, familiar food. Choose lower-fibre options before training.
30-45 Minutes Before (Quick Options)
Banana
The classic. Fast energy, easy to digest, portable. 25-30g carbs.
Natural Energy Bar
Designed for pre-workout. Look for carb-focused options, not protein bars.
Handful of Dates
Natural, fast-acting sugar. 3-4 dates gives you about 20g carbs.
Sports Drink
Liquid carbs if solid food feels heavy. Hydration and energy combined.
Morning HIIT Classes
Early morning sessions present a timing challenge. You can't eat 2-3 hours before a 6am class. Options:
- Small snack 20-30 minutes before: Banana, few dates, or small glass of juice
- Night before strategy: Eat a carb-rich dinner to maximise glycogen overnight
- Liquid calories: Sports drink or diluted juice if solid food doesn't sit well early
What About Fasted HIIT?
Fasted versus fed HIIT has been tested extensively. In studies comparing groups doing identical training protocols over 6 weeks, there's no significant difference in body composition or muscle adaptations between fasted and fed groups.
However, fasted exercise does not improve performance - the fed state consistently outperforms fasted for high-intensity work. While fasted training increases fat oxidation during the workout itself, this doesn't translate to greater long-term fat loss.
The takeaway: If your goal is fat loss, fasted HIIT won't hurt your results. If your goal is performance (hitting harder intervals, more power output), eat something beforehand.
Caffeine and HIIT
Caffeine is one of the most effective legal performance enhancers for high-intensity exercise. Here's what it does:
- Power output: Approximately 4% improvement compared to placebo
- Sprint performance: Significant improvements in power-based activities
- Reduced perceived exertion: Workouts feel easier at the same intensity
- Speed benefits: Improvements found in activities lasting as little as 60 seconds
Dosing: 3-6mg per kg bodyweight, taken 30-60 minutes before training. For a 70kg person, that's 210-420mg (roughly 2-4 cups of coffee). Effects are more pronounced in people who don't regularly consume caffeine. Be cautious with afternoon sessions if you're caffeine-sensitive, as it can affect sleep.
What to Avoid Before HIIT
- High-fat meals: Slow digestion means discomfort during burpees and sprints
- Large portions: A full stomach and jumping don't mix
- High-fibre foods: GI distress is common during intense exercise
- New supplements: Test everything in training, not before a class
- Protein-only meals: You need carbs for high-intensity work
- Excessive water right before: Bloating and sloshing during intervals
Hydration
HIIT produces significant sweat. Start hydrated rather than trying to catch up during the workout:
- Drink steadily throughout the day, not just before class
- 500ml of water 2-3 hours before is a good baseline
- Sip 150-250ml in the hour before (don't gulp large amounts)
- Urine should be pale yellow - clear or dark means adjust intake
Your Pre-HIIT Nutrition Summary
Carbs are essential: Carbohydrate availability directly impacts HIIT performance - nearly 3x longer time-to-exhaustion when properly fuelled. Timing: 1-4g carbs per kg bodyweight in the 1-4 hours before exercise. Fasted training: Won't harm body composition results, but performance will be lower. Caffeine: 3-6mg/kg bodyweight 30-60 minutes before can improve power output by ~4%. Hydration: Start hydrated - 500ml 2-3 hours before, sip steadily after.
After your HIIT session, recovery nutrition helps you adapt to the training. Read our guide on what to eat after HIIT for post-workout recommendations.
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