High-intensity interval training (HIIT) is one of the most time-efficient forms of exercise available — short sessions producing substantial cardiovascular and metabolic benefits. For London's time-pressed professionals, a 20–30 minute HIIT session fits into a lunch break or early morning slot that a longer endurance session could not. But the metabolic demands of HIIT are significant, and nutrition around sessions directly affects both performance during training and recovery after it.
What HIIT Does to the Body
HIIT works by repeatedly driving the body to near-maximal effort for short intervals (typically 20–60 seconds) followed by brief recovery periods. This creates significant metabolic stress: glycogen depletion in the working muscles, substantial EPOC (excess post-exercise oxygen consumption) that elevates metabolism for hours after the session, and strong adaptive signals for both cardiovascular and muscular adaptation.
The result is a training mode that is highly glycolytically demanding (burning carbohydrate rapidly during intervals) and produces significant muscle damage requiring protein for repair. Both of these nutritional requirements need to be addressed in the pre- and post-training window.
Pre-HIIT Nutrition
Performing HIIT in a fully fasted state is possible but suboptimal for most people. Without carbohydrate availability, the high-intensity intervals feel significantly harder, form breaks down earlier, and total training volume is reduced. A small carbohydrate-protein snack 60–90 minutes before a HIIT session — a banana, a small bowl of porridge, or a slice of wholegrain toast with nut butter — provides adequate fuel without causing digestive discomfort during high-intensity work.
For lunchtime HIIT sessions (common among City workers with access to a gym near their office), a light carbohydrate snack mid-morning rather than a full lunch before training, followed by a proper post-training lunch, is the most practical approach. The British Nutrition Foundation guidance on pre-exercise nutrition supports this light pre-session, substantial post-session approach for midday training.
Post-HIIT Nutrition: The Critical Window
After HIIT, the body is in a state of elevated protein synthesis (muscle repair) and glycogen resynthesis (fuel replenishment). Consuming a meal with both carbohydrates and protein within two hours of training maximises both processes. The specific targets: 20–40g of complete protein and 50–80g of carbohydrates in the first post-training meal, with the lower end appropriate for shorter sessions and the higher end for longer or particularly intense sessions.
For City workers returning from a lunchtime HIIT session, a Vanda's Kitchen Freedom Tray lunch — fresh, protein-forward, complex-carbohydrate-rich, delivered to your office — addresses this recovery window precisely. Our certified halal, 100% nut-free food provides the nutritional quality that post-HIIT recovery requires. View our team lunch options.
Hydration and Electrolytes After HIIT
HIIT produces significant sweat loss relative to its duration. Rehydrating after a session — consuming at least 500ml of water or an electrolyte drink in the two hours following training — supports recovery and prevents the cognitive performance decline that mild dehydration produces in the working hours after a lunchtime session. See our electrolytes and sport hydration guide.
HIIT Frequency and Recovery Nutrition
HIIT more than three times per week without adequate recovery nutrition leads to accumulating fatigue and overtraining risk. For professionals doing HIIT two to three times per week, consistent daily protein intake (1.4–1.8g/kg bodyweight), adequate total calories, and quality sleep are the foundations of sustainable adaptation. See our overtraining and recovery guide and our sleep and performance guide.
For authoritative exercise nutrition resources, the British Dietetic Association sport and exercise specialists publish evidence-based guidance on HIIT nutrition specifically.
Supporting Your Health Through Daily Nutrition
Understanding the principles covered in this article is valuable — but applying them consistently through daily food choices is where the real benefit comes. For London office workers, the quality of the daily work lunch is one of the most controllable nutritional variables in the day. A fresh, balanced, nutritious lunch delivered to your desk removes one decision from a demanding schedule and ensures a consistently good nutritional foundation.
Vanda's Kitchen near St Paul's Cathedral EC4 delivers certified halal, 100% nut-free, freshly prepared corporate catering across the City of London and central London. Our Filipino-inspired menu is built around lean proteins, fresh vegetables, and complex carbohydrates — the nutritional combination that supports energy, performance, and health throughout the working day. Every item we produce carries full allergen labelling in compliance with Natasha's Law, and our entire kitchen is independently certified halal by the Halal Friendly List.
Our Selfridges Food Hall presence confirms the quality standard we maintain. For London teams wanting consistently nutritious, genuinely delicious, allergen-safe daily lunches, Vanda's Kitchen is the straightforward answer. View our team lunch options, WhatsApp us for a same-day response, or send an enquiry. Read our healthy office lunch delivery guide for more on what we offer and how our delivery works.
Frequently asked questions
How long should I wait to eat before a lunchtime HIIT session?
A full meal two to three hours before is ideal, but impractical at lunchtime. A small carbohydrate-focused snack mid-morning — fruit, oatcakes, or a banana — one to two hours before the session is the most workable approach. This avoids training fully fasted while preventing the digestive discomfort that high-intensity exercise causes if a large meal was eaten recently.
Is fasted HIIT effective for fat loss or does it just impair performance?
Fasted HIIT modestly increases the proportion of fat oxidised during the session, but total energy expenditure is lower because intensity drops without carbohydrate availability. Over time, consistently lower training intensity produces less adaptation, and the metabolic benefit of fasted training does not compensate for the reduction in training quality. Adequately fuelled HIIT produces better body composition outcomes for most people over weeks and months.
How much protein do I actually need after a HIIT session?
Research consistently supports 20-40g of complete protein in the first post-training meal, with 20-25g sufficient for most people under 75kg and 35-40g more appropriate for larger individuals or particularly long sessions. Spreading protein across the rest of the day in subsequent meals matters as much as the immediate post-training dose — muscle protein synthesis remains elevated for 24-48 hours after HIIT.
Does coffee before HIIT improve performance?
Caffeine is one of the few ergogenic aids with strong, consistent evidence — it reduces perceived exertion, improves power output, and extends time to fatigue. Three to six milligrams per kilogram of bodyweight consumed 30-60 minutes before training is the effective range. For someone sensitive to caffeine, the anxiety and elevated heart rate it causes can impair rather than improve performance during high-intensity intervals.
How many rest days do I need between HIIT sessions for nutrition to support recovery?
Most exercise physiologists recommend 48 hours between HIIT sessions, which allows adequate muscle repair when protein intake is sufficient. Doing HIIT on consecutive days without adequate protein and carbohydrate recovery accelerates accumulated fatigue and increases injury risk. Two to three HIIT sessions per week with adequate nutrition between them produces better adaptation than more frequent, poorly recovered sessions.