The traditional approach to nutrition for endurance sports has involved eating plenty of carbohydrates to fuel your training sessions, together with a moderate amount of protein to support muscle repair, and the remainder of your calorie needs coming from fat. Plenty of pasta has been in order! You may well find that this works well for you and there is certainly research available to back up a high carb diet for runners, cyclists and triathletes.But recent years have seen some different approaches becoming more popular among endurance athletes. The concept of nutrition periodization, where you alter your calorie and macronutrient intake to match the different cycles in your training plan, is now well established, for example. I wrote about this in an earlier blog post. A sports dietician in the USA called Bob Seebohar, who has worked with the US Olympic Triathlon team and many professional triathletes and other athletes, did much to develop this concept. I am an admirer of his work, and recommend that you take the time to read his chapter on Nutrition for Endurance Athlete in The Complete Triathlon Guide compiled by USA Triathlon (Human Kinetics 2012) – you can buy the book or e-book here.
It’s another approach to nutrition for endurance athletes championed by Bob Seebohar, however, that is the subject of this blog post. This is improving your metabolic efficiency (ME), which is essentially teaching your body to rely more on its body fat stores for energy and less on its muscle glycogen stores. The lower the intensity you train or race at, the greater the proportion of energy that is metabolised from fat. As intensity increases, so does your reliance on glycogen. The more metabolically efficient you are, the higher the intensity you can reach before you cross over to burning more carbohydrate than fat. If you have a low metabolic efficiency point (MEP), you will be dependent on carbohydrate stores to maintain your pace even at a relatively low intensity and will need to take on extra carbs in the form of gels, drinks and bars during most training and races over an hour in length, in order to replenish your glycogen.
Needing to take on large amounts of carbohydrate has several disadvantages. Firstly, you are likely to be more prone to gastrointestinal distress as your body struggles to digest and absorb the carbs. Secondly, you need to carry large amounts of sports nutrition products with you (awkward and expensive). Thirdly, sustained high carbohydrate intakes may have adverse effects on your health in the longer term or body composition in the shorter term.
Improving your metabolic efficiency isn’t about eating a very low carbohydrate diet in order to induce a state of ketosis, another approach which is becoming increasingly popular among some recreational athletes (see another blog post that I wrote about this). It’s about training your body to be able to preserve its carbohydrate stores for longer, by burning predominantly fat at ever increasing intensities. There will always be a certain intensity point at which your body switches to using carbs, as you start to work anaerobically, eg when working in Zone 4-5, or at higher than about 92% of your VO2 max. But through improving metabolic efficiency it should be possible to increase your fat burning capacity when working at between 65% and 91% of VO2 max.
Although it can provide benefits for all, there are certain categories of endurance athlete who I believe would particularly benefit from taking the metabolic efficiency approach:
- Those who suffer from gastrointestinal distress during races
- Those who struggle to lose body fat
- Those who have a family history or increased risk of type 2 diabetes or cardiovascular disease
- Those who are participating in the longer endurance events, eg Ironman, ultra-marathons, multi-day cycling or run challenges.
There are two sides to improving metabolic efficiency: training and nutrition. The detailed training side is outside the scope of this blog but requires developing a good base of aerobic work during your preparatory cycle, with minimal high intensity workouts at this stage and plenty of volume done in Zone 1. This training allows the necessary mitochondrial changes to take place that alter the body’s efficiency in using fats as fuel.
Here are the key points that you need to know about implementing metabolic efficiency from the nutritional perspective:
- Lower your carbohydrate intake as a proportion of your calories during your base or preparatory training cycle. Eat more protein and healthy fats in its place. Get most of your carbs from vegetables, fruits, dairy products, legumes and nuts rather than wholegrains and sugars. If you feel hungry, eat some additional fats or protein.
- Avoid using sports nutrition products like drinks, bars and gels during base training when you are working at low intensity. Eat a small meal or snack, including some of the carb sources listed above, as well as some protein and fats, in the hour or two before you train. Then eat a similarly balanced meal or snack within 30 minutes of finishing, without using a recovery drink or bar.
- When you move into your build and competition training cycles and are doing more training at higher intensities, increase your carbohydrate intake by introducing more wholegrains on the days where you have your hardest or longest sessions. Have a small amount at each meal, rather than a large amount just before or after training. Maintain your previous intake of vegetables, fruits, protein foods and fats. This approach provides you with additional calories as well as sufficient glycogen to fuel your Zone 4-5 efforts, without adversely affecting your improved ability to burn fat at lower intensities.
- Re-introduce sports nutrition products as needed at this point. If your metabolic efficiency has improved you should find you need fewer grams of carbohydrate per hour than previously to maintain the same effort.
- On race days, focus your carbohydrate intake on the 24 hours before and 12 hours after your event. Develop a race nutrition plan that reflects your improved ability to burn fat. You will need some carbohydrate during long races, but it should be less than previously.
This is just a brief summary. If you want to improve your fat burning, I advise you to buy Bob Seebohar’s e-book ‘Metabolic Efficiency Training: Teaching Your Body to Burn More Fat’, which covers both nutrition and training. You can download a copy here. There is also a useful cookbook available to buy, giving simple recipes that follow the metabolic efficiency nutrition principles, and an excellent smoothie recipe book.
I would also suggest that you locate a facility that offers metabolic efficiency testing near you. This may be the lab at a university’s sports science department or one of an increasing number of private clinics. This enables your current metabolic efficiency point (crossover) to be measured in a graduated treadmill or stationery bike test and then re-tested after a period of training and nutritional changes, and can help you to fine tune your nutritional plan.
Let me know how you get on.
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