‘I’m a sports nutritionist – this is exactly what I eat and drink before exercising in hot weather’

Exercising outside during a heatwave is tough. You set out for your usual run or strength session, expecting to hit your normal splits or lift your planned weights, and 15 minutes later, you’re drenched in sweat, bright red in the face, and need to either take a walking break or dial down the weights.

But hot-weather workouts don’t have to feel this punishing if you get your fuelling and hydration right, according to sports nutritionist Anita Bean.

Below, she reveals exactly how she fuels before training in hot weather, when electrolytes are genuinely useful and the warning signs you should never ignore.

What I eat and drink before exercising in the heat

‘I aim to start every workout well hydrated by drinking around 400–600ml of water gradually over the two hours before exercise, rather than all at once just before starting,’ Bean explains.

‘If I’m exercising for longer than an hour, I’ll also have an easily digested, carbohydrate-rich meal two to three hours before training. That might be a bowl of muesli or overnight oats – made with around 50g oats and soya milk – topped with berries and a drizzle of honey, plus water.

‘If I’m training first thing or only have 30–60 minutes before exercising, I’d opt for something lighter, such as a banana, a slice of toast with honey or a homemade fruit and nut bar.

‘In very hot weather, I also like to include naturally hydrating foods such as melon, berries or yoghurt. If you struggle to eat early in the morning, a smoothie, diluted fruit juice or an isotonic sports drink can be easier to tolerate while still providing fluid and carbohydrates.’

How to fuel for different types of exercise in the heat

‘The longer and harder your session, the more important it is to start well fuelled and hydrated,’ Bean explains.

‘For a short strength session (up to around an hour), most people don’t need extra carbohydrates immediately beforehand if they’ve eaten a balanced meal within the previous few hours. Hydration is usually the main priority.

‘For a 45–60 minute run, a light carbohydrate snack beforehand – such as toast with jam or a banana – can help improve energy levels, particularly if you’re training first thing in the morning.

‘For endurance sessions lasting more than 90 minutes, I recommend starting well fuelled, drinking during exercise, and consuming carbohydrate throughout the session. Typically, that means around 30–60g per hour, increasing to 60–90g per hour during longer or higher-intensity events. Hot weather increases sweat losses, making it even more important to replace fluids and stay hydrated.’

How much should you drink when exercising in hot weather?

‘There’s no single amount that’s right for everyone, because sweat rates vary enormously – especially in the heat,’ she says. ‘Drinking 400–600ml over the two hours before exercise is a useful starting point. Then, drink to thirst during your session.

‘For most recreational exercisers, thirst is a reliable guide. However, if you’re exercising at a high intensity for longer than 90 minutes in hot conditions, a personalised hydration plan can help minimise dehydration.

‘One way to estimate your fluid needs is to calculate your sweat rate by weighing yourself before and after a training session – taking into account how much you’ve drunk during exercise.

‘Avoid drinking as much as possible ‘just to be safe’ – over-drinking can be just as problematic as dehydration.’

When are electrolytes actually necessary?

‘Electrolyte drinks are most useful during prolonged, high-intensity exercise (typically over 90 minutes), particularly in hot conditions or for people who sweat heavily or have very salty sweat,’ Bean explains.

‘They help replace sodium lost in sweat, encourage fluid retention and can stimulate thirst, making it easier to stay hydrated. For shorter sessions, plain water is usually sufficient.

‘After exercise, the goal is to replace both fluid and electrolytes lost through sweat. For most recreational exercisers, drinking water alongside a normal meal will achieve this. If you finish your session significantly dehydrated, you may benefit from a sports drink or electrolyte solution.’

The biggest hot-weather fuelling mistakes

‘The biggest mistake is starting exercise already dehydrated,’ Bean says. ‘Many people simply don’t drink enough during the morning before heading out.

‘I also see people under-fuelling before long sessions because they’re worried about stomach discomfort. An easily digested carbohydrate-rich meal or snack usually works much better than training on empty, particularly in hot conditions where exercise already feels more demanding.

‘Another mistake is ignoring the temperature and attempting to maintain your usual pace or intensity. On very hot days, slow down, shorten your session or exercise earlier in the morning or later in the evening, when conditions are cooler.’

The warning signs you shouldn’t ignore

‘Stop exercising if you experience dizziness, light-headedness, a headache, nausea, unusual fatigue, muscle cramps, chills or goosebumps despite the heat, excessive breathlessness, confusion or loss of coordination,’ Bean recommends.

‘Move into the shade or a cool environment, remove any excess clothing, begin cooling your body and drink fluids. If your symptoms are severe, don’t improve quickly, or you become confused, disoriented, or collapse, seek medical help immediately. These may be signs of heatstroke, which is a medical emergency.’