Pre-Exercise Nutrition

Spreading your energy consumption across the day is the perfect way to accommodate round-the-clock training sessions. Just keep an eye on those high-GI cabrs...


Issue ID: March 270


Your daily diet is the most crucial part of pre-exercise nutrition. Re-thinking meal timings and adopting a ‘five small meals a day’ approach works very well for triathletes, spreading energy intake evenly over the course of the day. This allows individuals to effectively fit meals and snacks around training sessions, maintain good energy levels and recover well.


Carbohydrates are a quick and efficient way to ingest the all-important sugars to the body, supplying readily available energy for performance. Understanding high- and low-GI carbohydrates (or fast-release and slow-release) is a vital step toward eating healthy carbohydrates, as well as ensuring a good supply of nutrients and fibre.

Carbohydrates are ranked using a scoring system called the Glycaemic Index (GI). The GI score of a food is based on the rate at which it breaks down into sugar (glucose), how fast it’s absorbed and how quickly it raises blood glucose levels. Carbohydrates that break down rapidly during digestion release glucose into the bloodstream very quickly and these have the highest GI scores. They provide a quick burst of energy, which lasts for a fairly short period of time. Examples of high-GI carbs include pure glucose, energy gels, biscuits, rice cakes, sweets and refined starches like white bread, overcooked pasta, mashed potato and white rice.

The blood glucose response of these foodsis fast and high, and in terms of sustaining appetite, they fail to satiate for long periods of time. Eating too many high-GI foods can also block the ability to burn fat. Unsurprisingly, these are the foods we need to minimise –
or look at replacements for – in the daily diet, using them only for fast-energy replenishment or for during exercise.

Carbohydrates that break down slowly, releasing their glucose gradually into the bloodstream, have low GI scores. Examples here include most fresh fruits (especially apples, pears, plums, oranges, grapefruits, raspberries and blueberries), unrefined carbs (such as brown rice, wild rice, quinoa, barley, dark whole rye bread, soy/linseed bread) and vegetables. The blood glucose response of these foods is slower and lower, providing longer-lasting energy and a more sustained feeling of fullness. These foods are generally higher in fibre and nutrients, too, and help enormously with boosting energy and fat loss, while helping to maintain a healthy, lean physique and healthy body composition.
A healthy diet should be based predominantly around low-GI natural foods.
Where possible, swap regular high-GI carbs for a lower alternative. For example, rye bread instead of white bread; oats to replace commercial cereals; and vegetables and wholegrain rice rather than potatoes.


Eating before training provides the necessary fuel and fluid to get the most out of the session. It can also give the athlete confidence that they’re suitably energised. 
What to eat and when largely depends on the time of the training session. If it’s first thing in the morning, a light snack 1-2hrs before is sufficient. Exercising later in the day calls for a meal 3-4hrs beforehand. In addition, sufficient fluid should be taken to maintain hydration.
Food should be relatively high in carbohydrate to maintain blood glucose, moderate in protein and composed of familiar foods well-tolerated by the athlete. A meal should also be low in fat and fibre to minimise any potential gastrointestinal distress.
For many, eating prior to exercise simply satisfies gnawing hunger pangs, although hunger isn’t always a good indicator of low body stores of carbohydrate – rather it’s just that the stomach is empty!


Training very early in the morning leaves little time for a pre-workout meal 3-4hrs before. In these instances, either a snack or liquid meal such as a milk smoothie or even a latte 1-2hrs prior can suffice, especially if the session is 60mins or less. In situations where there’s no time at all to spare, training on an empty stomach for sessions of 60-90mins is perfectly feasible and the norm for many athletes. That’s because the body will have sufficient carb stores to fuel at least 60mins of exercise (sometimes more than this).

In fact, well-trained athletes who areefficient at utilising fat stores as energy often choose water, tea or an espresso as their preferred pre-workout fuel. That said, this fasting shouldn’t be a daily norm as not only does food fuel the session, it also helps to optimise recovery. And if you’re training twice or more a day, you really should pencil in an early morning breakfast meal.

When it comes to what lies on the morning menu 1-2hrs before the workout, excellent meal choices featuring 200-400 of mainly carb calories include a bowl of oats or oatmeal; porridge with banana and yoghurt; a fruit and yoghurt smoothie; or a simple bowl of fresh fruit and yoghurt. These types of meals are easy to digest, contain a mix of low- and medium-GI carbohydrates with a little added protein and minimal fat, all of which will top up liver glycogen stores and help to keep blood sugar levels in check.

Incidentally, oats and oatbran can simply be soaked overnight in water and don’t necessarily need cooking, which is perfect if, say, you’re preparing breakfast in a hotel room. Bananas are particularly good as they’re easily digested and provide three natural sugars – sucrose, fructose and glucose. With the additional fibre content, bananas provide a boost of energy that’s both instant and sustained. Many swimmers and triathletes find it hard to eat solid foods prior to a swim session. In this scenario, carbohydrate drinks or smoothies often work best, or a small bowl of cooked porridge. Alternatives also include fresh fruits, particularly apples and bananas, bothof which are fast-digested and absorbed before a swim session.


Ideally, a moderate-sized meal should be eaten 3-4hrs prior to a daytime or evening training session. The focus should be on carbohydrate plus small-to-moderate amounts of protein. The focus should be on low-GI carbs, such as oats, sweet potato, brown rice, quinoa, barley and vegetables.

Good meal examples include oat-based cereals and banana; mixed rice and tuna; scrambled eggs on wholegrain toast; sweet potatoes with beans and salad; turkey or egg salad in a wholemeal pitta; or a bowl of chicken and vegetable stew. A small amount of protein in meals reduces the overall glycaemic index of the meal, which leads to a steadier release of glucose into the bloodstream during the upcoming session. Protein can also be used as a back-up fuel,
and helps to stimulate protein resynthesis following the session (the speed at which the body breaks down ingested protein to be utilised by the body).

It’s important to remember that food only becomes useful to the body once it’s been digested. Therefore you should allow sufficient time for a pre-exercise meal to fully digest. If you need something close to the start of a session or race, choose a piece of low-sugar fruit, such as an apple or banana. Although there’s little scientific evidence to show that carbohydrate taken during the hour immediately before exercise has negative effects on performance, it’s still not wise to take on board high-GI foods 20-30mins before the start. They cause a sharp rise in blood sugar, followed by a sharp rise in the hormone insulin. Insulin’s job is to swiftly clear the
blood of glucose in order to reduce levels.


The result is an equally swift drop in blood glucose, with a concomitant drop in energy, before things level out. But again, with all pre-exercise meals, the athlete must experiment to find the timing, amount and meal that suits their needs.