How to Fuel For Endurance Exercise

How to Fuel For Endurance Exercise

If you happen to pass through Richmond Park during this beautiful weather you may feel you have unwittingly entered a Team GB training camp. Closer inspection might reveal that a few bodies are not quite of Olympic standard. In fact, the park is brimming with endurance sports enthusiasts. ‘Mamils’ and ‘Willows’ (Women in luminous lycra on wheels) spin their gears getting ready to take on events such as la Marmotte, L’Étape du Tour and the Houte Route. Meanwhile runners are pounding the pavements in readiness for the Marathon du Medoc and the Midnight Sun Marathon. Fulham’s Triathletes, not to be left out, can be found hunched over tri bars out training for the Alpe d’Huez Triathlon and the Nice Ironman.

After all their exertions the Richmond Park coffee shop does a brisk trade. One of the most controversial areas in endurance sports at the moment is what food and drink to consume during endurance events and while training for them. All too often, nutritional strategy is overlooked.

Basics: Getting the simple things right.

The food you use during training or racing should be both portable and practical. Therefore, it shouldn’t melt in the heat or freeze in the cold. It is very important that the food you use during a race should be something you have used in your training. Race day is definitely not the time to experiment with a new food. Make sure you have tried the food during training and that it suits you digestive system.

Pre-Event: Carb loading is still popular.

Our bodies (mainly) burn two types of fuel: fat and carbohydrate (CHO). Compared to fat stores, our stores of carbohydrates are small. The main way we store CHO is as glycogen in the liver. Carbohydrate is a fuel that the body finds easy to use during exercise, so it’s a good idea to ensure you start with a full tank of glycogen. Prior to an event a common strategy is for the two days pre-event eat 5-7g/kg of carbohydrate rich food.

For breakfast pre-race aim to consume 100g CHO, this equates to large bowl porridge or 4 wholegrain pancakes.

Caffeine has been known to enhance sports performance. A moderate dose of caffeine equivalent to two cups of coffee can improve performance if taken 30-60 minutes prior to exercise. There doesn’t seem to be any additional benefit of higher doses but more caffeine may increase the risk of side effects such as jitteriness. Also, if you are not a habitual coffee drinker, the morning of a big event is not the time to start.

During the Event:

The general consensus amongst most in Sports Medicine is to try and ingest 30-60g CHO every hour by taking food every 20-30 minutes. The body can’t use more than 60g/hr of asingle type of carbohydrate so a food that contains a combination of glucose, sucrose, maltodextrin or soluble starch recommended. Energy bars can be useful for this and my personal favourite currently are Veloforte Natural Energy Bars. Fibre slows down gastric emptying so it can be helpful to choose a food that is low in fibre. For an ultra-event up to 80g/hr of a combination of carbohydrates is often recommended.

Many cyclists and runners use energy gels during training and racing. Gels come down to personal preference and certainly divide opinion amongst endurance athletes. They are easy to use and convenient but any doctor who has looked after endurance athletes will tell you that they can cause disastrous tummy-upset. They are probably best kept towards the end of an event for a quick burst of energy to get you through that last stretch.

Recently, there is a trend to look beyond gels and chew bars for fuelling during a race. To an extent this is driven by a desire by athletes for more natural foods with fewer additives. In part, the yearning for more natural food is due to concerns about long term health. For many athletes, it is taste fatigue – they have become bored of eating very sweet things during a race and are keen for something that does not look and taste like a molten pick ‘n mix.

However, the main reason most endurance athletes want to try alternatives to carbohydrate is to improve performance. Our fat stores are plentiful even in very lean people and fat releases almost double the energy of carbohydrates. The problem with carbs is that they require frequent doses which increases spikes in insulin that blocks fat burning therefore inhibiting the release of a bountiful source of fuel. Greater and more efficient energy release by our bodies means better results. By consuming fewer carbohydrates during periods of training, particularly when training at lower intensity, athletes can become more metabolically efficient at burning fuel. This technique, known as ‘race high, train low’ in addition to making athletes become better able to use fat as a fuel but also up the efficiency of our mitochondria which produces energy in our cells.

There a couple of new trends in sports nutrition that are worth mentioning as they are likely to become more popular over the coming years. The first is ketones. Ketone bodies act as a fuel for the body in certain circumstances such as starvation and when on very low carbohydrate diets. Some athletes now consume exogenous (not made by the body) ketones in the form of an ester to provide an additional fuel to the body. However, the taste of ketones has been likened to petrol and the cost is similarly exorbitant. Recently, more palatable and affordable drinkable ketones have become available and doubtless this will become an expanding market.

Another new-comer to the endurance fuelling market is superstarch. This is a slow release so doesn’t require as frequent dosing as the usual carbohydrates and is easily absorbed by the stomach and intestines. It also does not raise insulin levels. This is particularly helpful as raised insulin levels inhibit the body’s ability to burn fat. As it is slow release, Superstarch is usually consumed 30-45 minutes prior to an event.


After a big endurance event make sure you celebrate. Having a beer post-race will not impair hydration levels (for cyclists this will presumably be a suitably hipster craft IPA). A large carbohydrate and protein rich meal 2 hours after the event will help to restore the depleted glycogen stores and provide amino acids for those exhausted muscles. Just before bed 40g of protein in the form of a protein shake can help with muscle protein synthesis overnight and perhaps make the legs ache just a little less the next day.

Dr Hugh Coyne

Private GP, Coyne Medical, Parsons Green, Fulham