Endurance sports nutrition: state of the art in 2019 with prof. John Hawley | EP#181

Professor John Hawley is one of the leading researchers in the world on sports nutrition, the interaction between exercise and diet on fat and carbohydrate regulation, and the cellular and molecular basis of endurance sports adaptations. He gives us a complete update on what we actually know as of today about endurance sports nutrition, and where evidence is still lacking.

• Nailing the basics of endurance sports nutrition - what's most important top consider and get right?
• Getting clear on commonly misunderstood terminology in the field of nutrition. 
• Beyond the basics: the impact on endurance performance of manipulating carbohydrate availability, nutrition periodisation, and day to day diet. 
• Fat, carbs, and their impact on inflammation and recovery, insulin response, and body composition. 
• How do elite endurance athletes actually eat? 
• Common myths about and mistakes amateur athletes make with nutrition. 

4:35 -

• I started out doing economics as my first degree, but found I didn't have too much passion for it and switched to exercise physiology. 
• I did my undergraduate training at Loughborough in the UK when there were good runners around: Sebastian Coe, and others.
• I then went over to Dave Costas lab in the USA and did my Masters there. 
• I then did my PhD and post doctoral training at the University of Cape Town under Tim Noakes. 
• I'm now the director of the Mary MacKilop Institute of Health Research in Melbourne, Australia. 
  
  It's the exercise and nutrition research group which is a large group. 
  
  We study exercise and nutrition and their interactions, including their effects on training and on health. 
• We don't delve into pharmacological drugs so every study has a nutrition or exercise perspective. 

6:11 -

• Fat has probably been the most misunderstood. 
  
  The role of fat in the athletes diet has been overplayed. There is a role for it, both in athletes and inactive people, but it is a permissable role. 
• There has been a lot of bad press about carbohydrates, but it is an essential fuel if you're an endurance athlete or partaking in high intensity sports. 
  
  The higher intensity the exercise, the more you burn carbohydrate based fuels. This makes it absolutely essential. 
• Protein has come back into vogue, and there are many great labs (Luk van Loon in Maastrict, Stuart Philips in Canada) who have done a lot of work on the various types of protein for building muscle and cytopenia.
• I think a lot of people can stand to take in a bit more protein and drop some fat. 
• The bottom line is that fat, per gram, stores twice as much energy. 
  
  If you think of carbohydrate or protein, you get about 4 kilocalories per gram; with fat you get around 9.  
• For people who are predisposed to type 2 diabetes, carbohydrates can be dangerous because of the massive fluctuations of glucose that occur. 
  
  If you put that type of individual on a high carbohydrate diet, you're setting them up for failure in the long run. 
• Overall, if you're looking at the 'healthy' population (although unfortunately most of the population aren't healthy), then I don't think the recommendations for the proportion of fuels we take in has changed dramatically. 
• One thing that has changed is portion sizes. 
  
  The macronutrient composition of diets has not changed over 40-50 years, but the quantity of food and therefore the quantity of energy and calories is 2-3 fold greater. 

10:58 -

• Endurance athletes would define any event of a continuous nature lasting longer than around 30 minutes. 
  
  If you look at those events, the energy required to combust them is mainly coming from carbohydrates. 
• Almost all sporting events depend on carbohydrate and have some endurance component - even team sports. 
• As far as the 80/20 rule, for the endurance athlete the diet should be carbohydrate based. 
• The concept of what a high carb or low carb diet is massively confused in the media.
  
  People often think a high carb diet is eating as much starchy food (e.g. potatoes, bread, rice, pasta) as you can in a day, which isn't true at all. 
• Nutrition is great, but nothing replaces training - we eat to support our training. 
  
  Training is the 80, and nutrition is the 20 on top. 
• Regarding nutrition products I confer to my wife (Louise Burke), who is head of sports nutrition at the Australian Institute of Sport.
  
  The emphasis there at the last dozen years or so has been on food, rather than supplements, gels etc. 
  
  A lot of the products don't have vitamins, minerals, fibre or other things that are essential to the diet. 
• Sometimes I think we've lost track of normal food and what athletes should eat.
• If you're travelling in a remote place, or aren't able to sit down for breakfast after a training session, then some of the bars and gels are very god.
  
  However, they shouldn't be the basis of an athletes diet. 
• Food should be the priority, and the gels/bars/sports drinks should be the icing on the cake. 
• In terms of fuelling during training, it depends on the purpose of the session. 
  
  If it's an easy Saturday night, where the output is low to moderate and you want to burn fat, you want to abstain from carbs as long as possible. 
  
  However, if you want the ride to be at race pace then you'll want to supplement. 
• Nutrition should be tailored to the session, not the other way around. 
• Any time that you take in carbohydrate, your fat oxidation will immediately be suppressed. 
• Even a pre-training meal can blunt the breakdown of fat and can impair fat oxidation for several hours. 
• Subtle changes in nutritional status can massively alter the fuel balance of a training session. 
  
  Looking at work from George Brook's lab by Brian Bergman can help with this question. 
• The absolute intensity of exercise determines the total fuel bill.
• The relative intensity (how hard it is for you, percentage of maximal heart rate, rate of perceived exertion, percentage of VO2max etc) determines the fuel mix. 
  
  200 watts for a world class cyclist may mean burning exclusively fat, whereas 200 watts for a novice would be close to max and would be burning carbs. 
• On top of that, nutritional status can shift the curve from the right to the left as well. 

19:01 - 

• There was data published by Louise Burke and colleagues in the Journal of Physiology a couple of years ago, with athletes who were keto-adapted, meaning they'd been habitually on a high fat diet. 
• When the subjects are on a normal training diet (predominantly high in carbs) at a fixed sub-maximal work rate (50km race pace in this case) they burnt 0.5-0.6g fat/minute. 
• When they were shifted to a high fat diet and carbs were removed, that number doubled. 
  
  In some individual athletes it was more than double the initial rate of fat oxidisation in a chronic state. 
• The acute state would be less than that, but in a 4 hour ride if you change fat oxidation from 0.3 to 0.6g it will be quite substantial. 
• It's probably 20-30% in the acute case, but in someone who has had a high fat diet for weeks you can double the rate of fat oxidisation. 

31:19 - 

• Our paper recently published in the International Journal of Sports Nutrition and Exercise Metabolism is a helpful read here. 

• We became aware of the fact that athletes get very confused with the terminology. 
• One of the biggest buzz things going around at the moment is the ketogenic diet. 
• Everyone wants a quick fix - whether you're an athlete trying to get faster, or someone doing it for health and weight loss. 
• When I talk to athletes and they say they're on the ketogenic diet, I often ask about their breakfast and they'll tell me they had yoghurt and fruit. 
  
  They've probably had about 50g of carbs already.
  
  The definition of a ketogenic diet is that only 5% of your intake should come from carbs. 
  
  In practical terms, that's around 50g. 
• It's impossibly hard to have less than 50g of carbs a day unless you're seeing a dietician or a sports nutritionist. 
• To get an athlete in a ketogenic state is not difficult, you just need to drop the carbs to very low levels (as low as 25g a day).
  
  There are many trade offs - they are irritable, they can't train as hard, their sleep isn't as good. 
• When we do studies on this the teams feed the athletes for 3-4 weeks and know everything they intake. 
  
  Often athletes may think they are on a ketogenic diet but they often are not. 
• It's almost impossible to get an athlete to do this for longer than 3 weeks because they feel so bad. 
  
  It works for a very small percentage of athletes who are doing ultra endurance events that last several days or longer. 
  
  I don't feel it has a place in Olympic distance competitions. 
• We started the studies on high fat years ago - and we went in with a hypothesis of no difference - but we just did not find that it worked! 
• Ketogenic diets are different from low carbohydrate diets. 
• People often also think a high carb diet means eating as much carbohydrate as you can, which is not true at all. 
  
  Depending on the athlete/training session, a high carb diet may be 6-7g/kg body mass.
  
  A low carb diet, probably less than 3g/kg body mass. 
• The 'train low' idea is another one - how low does your muscle glycogen have to be to train low and get some of the benefits that periodised nutrition can give. 
  
  It's hard to put a number of it but I would say 50% of whatever your resting glycogen is. 
  
  There is obviously a threshold of glycogen in the muscle that is obligatory to do work in the first place.
• The early studies were done when athletes trained twice a day, doing a normal session in the morning then deliberately with-holding carbs before the second session. 
  
  In the lab studies we've performed we hit upon sessions that depleted 50% glycogen, so that's where I'm getting that number from. 
  
  40% may be better, but you need 50% minimum. 
• Quantifying this is difficult. If you go on the fact that you generally take in 400g, which is 1600 kilocalories of carbs, you are probably going to be pretty high in glycogen for the first session.
  
  We found that when athletes train with lowered muscle glycogen, on average their power outputs or speed are reduced by 7-8%.
  
  However the hormonal and metabolic milieu, and the adaptations in the muscle, are greater than when you do all your sessions with high glycogen. 
• When we did our first studies we did two sessions in a day, but the second session was compromised so we now do train high sleep low. 
• We found that if we give athletes their normal diet and we get them to train with high glycogen stores in the later afternoon or evening.
  
  As they have high stores the session is a high intensity one and is not compromised by a lack of glycogen. 
  
  We then deliberately with hold carbohydrate foods and put them to bed so they sleep low - in a low carbohydrate state. 
  
  The athlete then comes back in the morning fasted, ready for a session. They have the benefit of a high intensity session the night before and in the morning they do a long easy ride or run for 2-3 hours. 
  
  Their fat oxidation rates go through the roof. 
• By sequencing the order of training and nutrition, we've got the best of both worlds. 
  
  The high intensity training session is not compromised, the adaptations happen at a better rate at night, and the next morning they burn as much fat as the muscle can possibly oxidise. 
• This came through trial and error but mainly through athlete feedback. 
• We now have a robust and scientific model which we think is a good compromise. 
• Train low should not be done every day of the week.
  
  We did it twice a week or three times a week at most. 
• In the 4-6 weeks before an important race it can be beneficial to do more train low sessions in in the morning then. 
• If you have an injured athlete, it may be particularly beneficial to do some of these sessions to accelerate the training adaptation. 
• We generally use these sessions before major competition, stopping them 2-3 weeks out from the race. 

• All past nutrition episodes on That Triathlon Show

• Toward a Common Understanding of Diet–Exercise Strategies to Manipulate Fuel Availability for Training and Competition Preparation in Endurance Sport

• Swifter, higher, stronger: What’s on the menu?

• Maximizing Cellular Adaptation to Endurance Exercise in Skeletal Muscle

• Toward a Common Understanding of Diet–Exercise Strategies to Manipulate Fuel Availability for Training and Competition Preparation in Endurance Sport

• Respiratory gas-exchange ratio during graded exercise in fed and fasted trained and untrained men

• Effects of sleeping with reduced carbohydrate availability on acute training responses

• Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimens

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I am a full-time triathlon coach and an ambitious age-group triathlete. My goal is podium at the Finnish national championships within the next few years.

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