The optimal time to eat and drink prior to, during and after exercise is an issue that all endurance athletes must contend with if they want to maximise benefits from training or perform at their best in races. It’s also been the subject of many research studies over the last 20 years or so, which has sometimes led to conflicting conclusions. So, it is good to see the well-respected International Society of Sports Nutrition (ISSN) produce an updated position stand on Nutrient Timing recently (2017) 1, which makes practical recommendations for athletes about when to consume carbohydrate and protein. Currently the authors do not consider that there is sufficient research on the timing of fat intake to make recommendations. This may change when more conclusive research is available. The full article can be accessed here but the purpose of this blog to summarise the recommendations most applicable to people participating in endurance sport, and to add my practical tips to help you implement them.
What is Nutrient Timing?
Nutrient timing means methodically planning your food and, if using, your sports nutrition products. The timing of energy intake and the ratio of certain macronutrients (ie carbohydrate and protein) may enhance recovery and muscle tissue repair, augment muscle protein synthesis, optimise body composition and improve mood states following high volume or intense exercise. In turn, this should result in improved adaptations to training and better race performances.
Daily Carbohydrate Intake
Before examining the timing of carbohydrate intake, the ISSN gives recommendations on total daily carbohydrate intake for endurance athletes.
ISSN Recommendation: Daily carbohydrate intake should range from 5-12g per kg of bodyweight daily, and the amount should vary within this range depending on the amount and intensity of endurance activity. Typically, an endurance athlete training at moderate to high intensity (more than 70% of VO2max) for 12 hours a week should aim for an average of 8-10g/kg daily to maximise the glycogen stores in their liver and skeletal muscle. The total amount of carbohydrate is more important than aiming for a certain proportion of your calories to come from carbohydrate.
- Your overall calorie intake should, of course, be higher on days when you are training for longer and the additional calories should come primarily from carbohydrate rather than protein or fat. Your daily consumption of these other macronutrients should remain constant.
- Most of your carbohydrates should come from wholefoods, eg oats, rice, wholegrain bread, potatoes, sweet potatoes, vegetables, fruit and dairy products. Eating substantial amounts of refined carbohydrates such as cakes, biscuits, desserts and pastries will not help your long-term health.
- On your heavier training days, top up your carbohydrate intake as necessary to reach your target intake with larger portion sizes of the above wholefoods, together with additional sugars from honey, fruit and yogurt based-smoothies, fruit juice, dried fruit and better-quality energy bars (those made primarily with wholefoods such as oats, dried fruit and nuts).
- The sports nutrition products like carbohydrate drinks, gels, blocks and bars which you use on your longer training sessions do, of course, count towards your carbohydrate intake. Further guidelines on this are given below.
- Use an app like My Fitness Pal for 1-2 weeks to record a food diary which will show how much carbohydrate you are consuming on different days and how many grams of carbohydrate are contained in a serving of foods that you eat frequently. Use this information to plan your daily carbohydrate intake going forward so that it matches the demands of your training.
- You may want to experiment with “low glycogen training” which involves doing some of your lower intensity sessions in a deliberately carbohydrate depleted state. This topic is not covered in the ISSN review, but it is important to plan the timing of your carbohydrate intake when doing these sessions. You can more about how to do this in my blog here.
Use of carbohydrate during training and racing
ISSN recommendation: consume carbohydrate at regular intervals during training sessions and races which last more than 70 minutes and where the intensity is moderate to high (65-80% of VO2max). This maintains blood glucose levels and enables optimal performance.
- Aim for 30-60g of carbohydrate per hour, at intervals of between 10 and 15 minutes. The longer the session or the higher the intensity, the more carbohydrate required per hour. You are likely to need more carbohydrate in races than in training sessions.
- Use sports drinks, energy gels, blocks or chews, or energy bars, or possibly dried fruit or bananas if you prefer an unprocessed option. Know how much carbohydrate is in each product and plan your intake accordingly. Set an alert on your watch or bike computer to remind you to eat or drink. Don’t wait until you feel hungry or thirsty.
- On warmer days, take more of your carbohydrate as sports drink to help you stay hydrated. Dilute your drink if necessary to provide more fluid vs carbohydrate.
- Ensure that you practice your race day nutrition plan, which is likely to involve consuming a higher amount of carbohydrate than in training. If you struggle with carbohydrate intake during races, try these strategies to train the gut 2:
- Train with relatively large volumes of fluid, to train the stomach to handle it.
- Train immediately after a meal to get used to exercising with food in the stomach
- Train with relatively high carbohydrate intake during exercise to learn to tolerate this, eg 60-80g/kg (or up to 60g/kg if you currently use c 30-40g/kg)
- Increase the carbohydrate content of your daily diet, to improve the capacity to absorb and oxidise it.
Carbohydrate intake before races
ISSN recommendation: consume snacks or meals high in carbohydrate for several hours before races performed at over 70% of VO2max for 90 minutes or more. However, an adequate balance between rest and fuel is required for events starting in the early morning, and the consumption of too much food or fluid prior to exercise may result in digestive distress.
- Use the day before your event, or two days before in the case of events lasting 8 hours or more, to maximise your glycogen stores by consuming 8-12g of carbohydrate per kg of body weight, spread across 5-6 meals and snacks. Use sports drinks or fruit juice if you are struggling to meet this amount with solid food.
- Have your pre-race breakfast around 3 hours before your event starts, having gone to bed early if necessary to do this. This breakfast should be largely carbohydrate based and low in fibre, so avoid wholegrain sources of carbohydrate, especially if you are prone to digestive issues while racing. White bread or rice pudding with honey or jam and a banana typically works well, although pre-race breakfast preferences are very individual. Practice your pre-race breakfast prior to a long training session, at the time of day you will be eating it on race day. At 4am if necessary!
- Have a gel and some water or 250-350ml of sports drink (20-30g of carbohydrate) around 45 minutes before the race starts.
Carbohydrate intake after exercise
ISSN recommendation: consuming carbohydrate after exercise is an efficient nutrient timing strategy to maximise the replenishment of glycogen stores. There are two situations where the timing of this carbohydrate intake has been shown to be particularly important: when glycogen needs to be restored rapidly and when inadequate carbohydrate has been consumed before or during training. In these cases, consume 0.6-1.0g/kg of carbohydrate within 30 minutes of finishing exercise, and again every two hours for the next 4-6 hours. If you require full glycogen stores again within four hours, consume 1.2g/kg of carbohydrate per hour until your next session. Also try adding caffeine at 3-8mg/kg to promote glycogen restoration. If you cannot exceed a carbohydrate intake of 0.8g/kg/hr, add 0.2-0.4g/kg/hr of protein until the subsequent session.
- If you are training less than 4 hours later, consume 1.2g/kg of carbohydrate within 30 minutes and repeat hourly until your next session. Have 1-2 cups of coffee to aid glycogen restoration. If you prefer a lower amount of carbohydrate, combine 0.8g/kg with c 10-20g of protein, eg in a recovery drink, and drink hourly.
- If you are training twice in the same day, but not within four hours, make sure that you have 0.6-1.0g/kg of carbohydrate within 30 minutes and include the same at your subsequent meals.
- If you have deliberately trained with low glycogen stores (the strategy I mentioned earlier), the same applies.
- If you struggle to take on 30-60g/hr of carbohydrate during training sessions over 70 minutes, eg due to digestive problems, prioritise carbohydrate in your recovery meal or snack and every two hours for the rest of the day.
- If you are meeting your overall daily carbohydrate requirements through your meals and snacks, and are not training again the same day, the timing of post-exercise carbohydrate intake is much less important. However, it is still wise to make carbohydrate foods the major part of your post-exercise meal or snack, and eat this within 1-2 hours.
Most of the ISSN’s recommendations on the timing of protein intake relate to resistance training and muscle hypertrophy. However, there are a few points which are worth noting for endurance athletes:
- Little is known about the effect of protein consumption prior to endurance exercise. The fuelling focus should be on carbohydrates.
- When carbohydrate intake cannot be adequately maintained, adding protein may help to increase performance, prevent muscle damage, keep blood sugar stable and facilitate glycogen re-synthesis. This may be of value in longer distance endurance events.
- Consuming sufficient protein across the day (1.4-2.0g/kg in total), approximately every 3 hours, is more important than the precise timing of that protein intake around exercise. Include 10-25g protein at every meal and snack to achieve this. Use an app like My Fitness Pal for 1-2 weeks to check how much protein you are consuming and how many grams are in the foods you eat most frequently.
- Having 30-40g of slow-release casein protein 30 minutes before bed appears to increase muscle protein synthesis. This may be a useful strategy if you are looking to increase lean muscle mass.
The ISSN position stand makes it clear that their recommendations are based on studies with limited numbers of participants, primarily men. There is some evidence that females oxidise more fat compared with males, and utilise their glycogen stores to different degrees. It may be that women need a lower amount of carbohydrate relative to body weight than men. More research is required in this area before a firm recommendation on carbohydrate intake for female endurance athletes is made.
Research shows that there are performance benefits to specifically timing your carbohydrate intake, as well as the amount that you consume, before, during and after training sessions and races. Where practical, I suggest that you follow the ISSN recommendations, but always within the context of how long and how hard your training sessions are. To get the best out of this approach, you do need to plan your carbohydrate intake along with your training, and know the amount of carbohydrate in the foods and sports nutrition products that you consume regularly. There is less evidence around the timing of protein intake, but you should aim to meet your daily requirement by consuming protein-containing foods several times over the course of a day.
I hope you found this blog useful.
Jo Scott-Dalgleish BSc (Hons) is a BANT Registered Nutritionist, writing and giving talks about nutrition for endurance sport. Based in London, she also works as a Registered Nutritional Therapist, conducting one–to–one consultations with triathletes, distance runners and cyclists to help them eat well, be healthy and perform better through the creation of an individual nutritional plan. To learn more about these consultations, please visit www.nutritionforendurancesports.co.uk
1 Kerksick et al. International Society of Sports Nutrition Position Stand: Nutrient Timing. 2017. JISSN. 14:33. https://www.ncbi.nlm.nih.gov/pubmed/28919842
2 Jeukendrup AE. Training the gut for athletes. Sports Med. Mar 2017. 47 (Suppl 1): 101-110. https://www.ncbi.nlm.nih.gov/pubmed/28332114