Today I've been lucky enough to have Simon Whyatt guest blog for me. Simon runs the brilliant Primal Fitness outdoor personal training organisation and blogs about Primal Living (note: not Paleo). I thought of him last week when I listened to the second interview that the Marathon Talk Podcast team interview Professor Tim Noakes. In this interview, Noakes talks in detail about his diabetes and views on diet for endurance. A lot of what he discussed I felt chimed with Simon's views, so I asked him to listen again, consider and give some guidance to readers of this blog. To get the most out of this post, I recommend you listen to the interview here (from minute 47:30), then read on with what Simon has written.
So, over to you Simon. Lead on!
Stuart has asked me to write a post, detailing my thoughts on the dietary recommendations made by Professor Tim Noakes, as outlined in his interview on the MarathonTalk Podcast.
Before listening to the podcast in full, I had the impression that Prof. Noakes advocated a “low-carb paleo diet” as a sensible option for endurance athletes in general, and was ready to fully debunk this notion.
Having listened to the interview in full, however, I quickly realised this is not exactly what Prof. Noakes is recommending, though I would like to clarify a few points, raise a few questions, and perhaps make some slightly different suggestions.
Before I get into addressing Prof. Noakes claims directly, I thought a bit of background may be useful:
What is a “Paleo Diet”?
First up, for those that may not be aware, a “paleo diet” is a diet comprised only of foods eaten by our hunter-gatherer ancestors prior to the agricultural revolution. Essentially, just meat, fish, eggs, fruits and vegetables.
The argument goes that as there has not been sufficient time and/or selection pressure, human beings have not fully adapted to modern foods such as dairy products or cereal grains. Proponents of the diet claim that it is the presence in the diet of these “unnatural foods” that are the cause of many modern diseases including obesity, metabolic syndrome, cancer, autoimmune disorders and much more.
Many advocates of the paleo diet also claim that it should be a low-carb diet, and that excessive carbohydrate consumption is also a major contributor to the “diseases of civilisation”.
Now, there are quite a few problems with a lot of these assumptions, and to explore all of them would require an epic post, so I’ll just focus on the main ones:
1) There are so many lifestyle factors that changed along with diet that it is impossible to pin all our modern health woes on diet alone, let alone which factors of the diet.
2) The diets eaten by hunter-gathers, both ancestral and the few remaining contemporary tribes still following the lifestyle, have been shown to be incredibly varied, with many being comprised largely of carbohydrate - some up to 90% of calories from starchy root vegetables and fruits, whilst still exhibiting none of the symptoms of metabolic syndrome or chronic lifestyle related disease.
Can carbohydrates be a problem?
What I was pleased to hear from the interview, is that Prof. Noakes does recognise that carbohydrates are not necessarily a problem for everyone, and that it is really only those suffering from problems with carbohydrate metabolism that need to avoid them. He also indicates that he may now believe that this restriction may only need to be for certain types (i.e. the individual that got the results from cutting out sucrose alone), or for a certain period of time.
There are basically two issues at stake here.
1) The issue of carbohydrate tolerance AKA insulin sensitivity, what affects it, and whether it can be altered.
2) The categorisation of different carbohydrates.
Inflammation and Insulin Sensitivity
A growing body of evidence is showing “chronic inflammation” to be an underlying causal factor in pretty much all of today’s chronic lifestyle related illnesses mentioned above, from heart disease and obesity, through to cancer and depression, and of course type II diabetes and its precursor insulin resistance.1
Any athlete will be familiar with the concept of inflammation when it comes to an injury such as a sprain. Chronic inflammation is different however, as it occurs at a cellular level, and you will not be aware at the conscious level that it is occurring.
When someone becomes insulin resistant, they lose the ability to process carbohydrates in the normal manner, with more and more insulin being required to have the same effect, until it ceases to have any effect at all.
Early theories were that it was excessive consumption of carbohydrates themselves that led to the condition, but this now appears to have been incorrect. Rather it seems that there are many varied factors that can lead to chronic inflammation, and thus insulin resistance (and many other chronic diseases).2
It is possible that as Prof. Noakes suggests, excessive consumption of fructose in the form of sucrose and HFCS in processed foods and sugar sweetened beverages is one such factor, however there are likely many more, for example:
Why the term Carbohydrate is not particularly useful
The problem with the term carbohydrate, is that it is far too general, and is used to describe many different foods with vastly different characteristics and effects on the body.
In the strictest sense, carbohydrate means sugar.
Examples would include monosaccharides (single sugar molecules) such as glucose and fructose, disaccharides (two sugar molecules) such as sucrose (1 glucose + 1 fructose) and lactose (1 glucose + 1 galactose), oligosaccharides (a “few” sugar molecules) typically found in fruits and vegetables, and polysaccharides (many sugar molecules) which comprise the majority of starchy carbohydrates including potatoes, rice and pasta, the items most commonly brought to mind by the term “carbs”.
Though they all share many attributes in terms of chemical structure, the manner in which they are processed by the body vary widely: They are absorbed in different parts of the gut via different pathways, they are acted upon by different bacteria, and they are transported to, and used by, different parts of the body.
Matters are further complicated by the fact that these sugars, or chains of sugars are rarely consumed in isolation.
Wheat for example is a mix of different length oligo and polysaccharides, along with indigestible fibre, and various fats and proteins. Considering it as simply a carbohydrate is grossly misleading.
Anyway, with that little bit of background, let me get back to the original question:
Can a low-carb paleo diet be useful for endurance athletes?
My short answer would be no, a low carb paleo diet is not a good idea for an endurance athlete.
However, a short-term low carb paleo diet may be very useful for an individual looking to lose weight or improve their health, and a high carb paleo-ish diet could very well improve the health and performance of a great deal of endurance athletes.
Recommendations for individuals looking to lose weight
If you are carrying excess body fat there are a few things to consider:
1) You are suffering from some degree of insulin resistance caused by inflammation
2) You are over consuming calories
3) You should probably not be training for an endurance event
Although the exact mechanisms are not known, over the short-term, reducing carbohydrate consumption without counting calories has been shown to help people spontaneously reduce energy intake and contribute to weight-loss.
Eating a diet comprised predominantly from lean meat and/or fish and fibrous vegetables will provide the highest amount of vitamins and minerals possible per kCal, and is extremely satiating. This enables one to lose body fat (relatively) quickly and easily, without depriving the body of any essential nutrients.
I would strongly recommend against individuals wanting to lose weight from training for an endurance event, particularly one which involves running, for a number of reasons:
1) It puts a lot of stress on the joints and can likely result in injury ultimately making you more sedentary
2) In many individuals endurance training disproportionately increases appetite leading to an overconsumption of calories
3) It increases overall stress on the body, thus potentially contributing to inflammation
Instead of endurance training I’d recommend lots of easy low intensity activity such as walking or easy cycling for 30 mins each day.
Before considering any other mode of exercise, I would first advise:
a) Getting more sleep, looking to achieve a minimum of 8 hours.
b) Minimising/Learning to manage stress from other sources
(Hey, I never said this was going to be easy!)
Once this is in order some short bouts of high intensity strength and/or interval training are your best bet.
Recommendations for Endurance Althletes
My first question to anyone looking to take part in an endurance event is what are your motivations behind doing so?
I personally love endurance type events - I like to test the limits of my body, and I love being in the great outdoors.
I am under no illusion, however, that either taking part in, nor training for marathons, triathlons or ultra events is “good for your health”. On the contrary, they can take a serious toll on your body.
The focus of my exercise, training and nutrition approach is to keep my body healthy in order that my body can “endure” such events, not only now, but long into the future.
Deviating slightly from the topic, I’d recommend that unless you are a professional athlete, reducing your training volume, and including more short duration, high intensity work along with a minimalist strength training routine is the most sensible option to stay healthy in the long run.
From a dietary perspective I’d recommend doing the bulk of your training in either the fasted state, or a carbohydrate depleted state as this has been shown to both help burn body fat (the less bodyfat you have, the better your power to weight ratio), and increase your body’s efficiency at burning fat during an event, thus preserving carbohydrate stores for when you really need them.3
When it comes to actual race day performance, there is little question in the scientific literature that for endurance events of marathon distance or longer, carb intake is important, both in the days preceding the race, and during the event itself.4,5
That said, not all carbs are created equal, so choosing which foods and supplements one fuels one’s body with can make a huge difference to one’s performance and long term health.
Optimal Carb Loading
Pasta is an old carb-loading favourite of many endurance athletes, however it may well be an ill advised choice for many for a number of reasons:
1) You may be an undiagnosed celiac. It’s relatively unlikely, maybe 1-3 in 100, but certainly possible. Famously tennis star Novak Djokovic made great leaps in performance after discovering he had the condition. Even if you’re not celiac, it is thought around 6% of people suffer from wheat allergy and approximately another 6% from gluten-sensitivity. All in all that’s potentially 1 in 6 people who will benefit tremendously from avoiding the ubiquitous grain!6
2) Digestive distress. Wheat is high in oligosaccharides which are fermented by bacteria living in the gut. If you have an overgrowth of these bacteria in the small intestine, or the wrong kinds of microbes this can lead to the symptoms of IBS. Not what you want if you’re trying to carb load or take part in an endurance event!
If not pasta, then what should one carb load with? The following is my carb loading continuum, from best, to worst:
1) White Rice (or even rice pudding)
Low in indigestible fibre, anti-nutrients and toxins, white rice is essentially pure glucose. It’s very easy to digest, won’t bloat you or cause inflammation. The sugar in the rice pudding will add extra carbs, and the fructose will help fill the hepatic glycogen stores in the liver.
2) Starchy Root Vegetables (peeled)
White potatoes, sweet potatoes, yams etc. Make sure they’re well cooked, and consider mashing them to aid digestion further.
3) Sports drinks/Glucose solution
Research shows that to really improve performance athletes should take on up to 7g of carbohydrate per kg of bodyweight per day in the 2-3 days leading up to an endurance event of marathon distance or longer. This equates to an awful lot of food! Drinking a solution of glucose or 3:1 glucose:fructose solution along with your meals can make it easier to reach your target carb consumption without exploding!
4) Oats and other alternative grains
Oats and some other grains such as rye and spelt may be a better choice than wheat, particularly if soaked, sprouted and fermented properly first. Though perhaps not as good physiologically as the above, they can add some variety and taste to your pre-race diet. You’re not a robot after all! It could still be worth going 100% grain free for at least 30 days however, and seeing what effect this has on your performance, and then what happens when they’re reintroduced.
5) Legumes
As above, except these tend to be even more filling, and thus make it hard to consume enough calories/carbs.
6) Fruits and vegetables
Though these should comprise the majority of the bulk of your diet under normal circumstances, the high fiber content makes them very filling, and therefore not a good choice if your aim is to take on as much energy in the form of carbohydrate as possible! They are a bad choice for carb loading for exactly the reason they are a good choice for weight loss.
Race Day Nutrition
Despite the misleading title, this study indicates that, providing you have carb-loaded in the days preceding the race, it makes no difference whether you have a high fat or high carb breakfast.7
My recommendation for pre-race breakfast is to eat a meal you enjoy, have tested before, and know won’t cause you digestive distress.
In terms of in race nutrition, as distance increases, the more carbs you can ingest, the better you’re likely to do. A recent study suggests that taking on as much as 48-78g of carbs per hour produces optimal performance, with the caveat that this is only if you can stomach it!8
As glucose, maltodextrin and fructose are all absorbed via different pathways, finding a product that is a blend of all three should produce the best results.
Why am I doing all this?
Just a call to remember to ask yourself why you’re doing all this again.
No matter what the distance, the fact is if you’re well trained, and used to eating a healthy whole foods diet, you should be able to complete the distance with no carbs whatsoever.
Carb loading and using sports drinks and gels may help you do it faster but this is really only proven in high level athletes. It could be worth asking yourself if stuffing yourself silly for 3 days, then spending a fortune on disgusting tasting carb gels and drinks during your event is really worth it?
Personally I just eat some tasty rice and potato dishes in the days preceding the race to satiety, have a bowl of porridge, raisins and honey in the morning because I enjoy the taste, and take some dates, dried bananas and NAKD bars out the event with me because I like them!
1. http://www.nutritionandmetabolism.com/content/9/1/32
2. http://wholehealthsource.blogspot.co.uk/2011/08/carbohydrate-hypothesis-of-obesity.html
3. http://www.ncbi.nlm.nih.gov/pubmed/22805754
4. http://www.ncbi.nlm.nih.gov/pubmed/21590642
5. http://sweatscience.com/the-more-you-eat-the-faster-you-go-in-ultraendurance/
6. http://www.biomedcentral.com/1741-7015/10/13
7. http://www.ncbi.nlm.nih.gov/pubmed/22852054?dopt=Abstract
8. http://sweatscience.runnersworld.com/2012/10/the-optimal-carbohydrate-dose-for-endurance/
Before listening to the podcast in full, I had the impression that Prof. Noakes advocated a “low-carb paleo diet” as a sensible option for endurance athletes in general, and was ready to fully debunk this notion.
Having listened to the interview in full, however, I quickly realised this is not exactly what Prof. Noakes is recommending, though I would like to clarify a few points, raise a few questions, and perhaps make some slightly different suggestions.
Before I get into addressing Prof. Noakes claims directly, I thought a bit of background may be useful:
What is a “Paleo Diet”?
First up, for those that may not be aware, a “paleo diet” is a diet comprised only of foods eaten by our hunter-gatherer ancestors prior to the agricultural revolution. Essentially, just meat, fish, eggs, fruits and vegetables.
The argument goes that as there has not been sufficient time and/or selection pressure, human beings have not fully adapted to modern foods such as dairy products or cereal grains. Proponents of the diet claim that it is the presence in the diet of these “unnatural foods” that are the cause of many modern diseases including obesity, metabolic syndrome, cancer, autoimmune disorders and much more.
Many advocates of the paleo diet also claim that it should be a low-carb diet, and that excessive carbohydrate consumption is also a major contributor to the “diseases of civilisation”.
Now, there are quite a few problems with a lot of these assumptions, and to explore all of them would require an epic post, so I’ll just focus on the main ones:
1) There are so many lifestyle factors that changed along with diet that it is impossible to pin all our modern health woes on diet alone, let alone which factors of the diet.
2) The diets eaten by hunter-gathers, both ancestral and the few remaining contemporary tribes still following the lifestyle, have been shown to be incredibly varied, with many being comprised largely of carbohydrate - some up to 90% of calories from starchy root vegetables and fruits, whilst still exhibiting none of the symptoms of metabolic syndrome or chronic lifestyle related disease.
Can carbohydrates be a problem?
What I was pleased to hear from the interview, is that Prof. Noakes does recognise that carbohydrates are not necessarily a problem for everyone, and that it is really only those suffering from problems with carbohydrate metabolism that need to avoid them. He also indicates that he may now believe that this restriction may only need to be for certain types (i.e. the individual that got the results from cutting out sucrose alone), or for a certain period of time.
There are basically two issues at stake here.
1) The issue of carbohydrate tolerance AKA insulin sensitivity, what affects it, and whether it can be altered.
2) The categorisation of different carbohydrates.
Inflammation and Insulin Sensitivity
A growing body of evidence is showing “chronic inflammation” to be an underlying causal factor in pretty much all of today’s chronic lifestyle related illnesses mentioned above, from heart disease and obesity, through to cancer and depression, and of course type II diabetes and its precursor insulin resistance.1
Any athlete will be familiar with the concept of inflammation when it comes to an injury such as a sprain. Chronic inflammation is different however, as it occurs at a cellular level, and you will not be aware at the conscious level that it is occurring.
When someone becomes insulin resistant, they lose the ability to process carbohydrates in the normal manner, with more and more insulin being required to have the same effect, until it ceases to have any effect at all.
Early theories were that it was excessive consumption of carbohydrates themselves that led to the condition, but this now appears to have been incorrect. Rather it seems that there are many varied factors that can lead to chronic inflammation, and thus insulin resistance (and many other chronic diseases).2
It is possible that as Prof. Noakes suggests, excessive consumption of fructose in the form of sucrose and HFCS in processed foods and sugar sweetened beverages is one such factor, however there are likely many more, for example:
- Stress - Either emotional i.e. work or relationships, or physical i.e. over-training, illness or injury
- Dysbiosis - An imbalance of the gut flora (Noakes is right on track if he goes down this rabbit hole) potentially caused by bad diet, antibiotics or infection.
- Diet - Excessive toxins in the diet, food allergens, or an imbalance/deficiency of essential nutrients
- Overconsumption of Calories - Simply eating too many calories can lead to inflammation, which in turn can lead to over consuming calories. Talk about a vicious cycle!
Why the term Carbohydrate is not particularly useful
The problem with the term carbohydrate, is that it is far too general, and is used to describe many different foods with vastly different characteristics and effects on the body.
In the strictest sense, carbohydrate means sugar.
Examples would include monosaccharides (single sugar molecules) such as glucose and fructose, disaccharides (two sugar molecules) such as sucrose (1 glucose + 1 fructose) and lactose (1 glucose + 1 galactose), oligosaccharides (a “few” sugar molecules) typically found in fruits and vegetables, and polysaccharides (many sugar molecules) which comprise the majority of starchy carbohydrates including potatoes, rice and pasta, the items most commonly brought to mind by the term “carbs”.
Though they all share many attributes in terms of chemical structure, the manner in which they are processed by the body vary widely: They are absorbed in different parts of the gut via different pathways, they are acted upon by different bacteria, and they are transported to, and used by, different parts of the body.
Matters are further complicated by the fact that these sugars, or chains of sugars are rarely consumed in isolation.
Wheat for example is a mix of different length oligo and polysaccharides, along with indigestible fibre, and various fats and proteins. Considering it as simply a carbohydrate is grossly misleading.
Anyway, with that little bit of background, let me get back to the original question:
Can a low-carb paleo diet be useful for endurance athletes?
My short answer would be no, a low carb paleo diet is not a good idea for an endurance athlete.
However, a short-term low carb paleo diet may be very useful for an individual looking to lose weight or improve their health, and a high carb paleo-ish diet could very well improve the health and performance of a great deal of endurance athletes.
Recommendations for individuals looking to lose weight
If you are carrying excess body fat there are a few things to consider:
1) You are suffering from some degree of insulin resistance caused by inflammation
2) You are over consuming calories
3) You should probably not be training for an endurance event
Although the exact mechanisms are not known, over the short-term, reducing carbohydrate consumption without counting calories has been shown to help people spontaneously reduce energy intake and contribute to weight-loss.
Eating a diet comprised predominantly from lean meat and/or fish and fibrous vegetables will provide the highest amount of vitamins and minerals possible per kCal, and is extremely satiating. This enables one to lose body fat (relatively) quickly and easily, without depriving the body of any essential nutrients.
I would strongly recommend against individuals wanting to lose weight from training for an endurance event, particularly one which involves running, for a number of reasons:
1) It puts a lot of stress on the joints and can likely result in injury ultimately making you more sedentary
2) In many individuals endurance training disproportionately increases appetite leading to an overconsumption of calories
3) It increases overall stress on the body, thus potentially contributing to inflammation
Instead of endurance training I’d recommend lots of easy low intensity activity such as walking or easy cycling for 30 mins each day.
Before considering any other mode of exercise, I would first advise:
a) Getting more sleep, looking to achieve a minimum of 8 hours.
b) Minimising/Learning to manage stress from other sources
(Hey, I never said this was going to be easy!)
Once this is in order some short bouts of high intensity strength and/or interval training are your best bet.
Recommendations for Endurance Althletes
My first question to anyone looking to take part in an endurance event is what are your motivations behind doing so?
I personally love endurance type events - I like to test the limits of my body, and I love being in the great outdoors.
I am under no illusion, however, that either taking part in, nor training for marathons, triathlons or ultra events is “good for your health”. On the contrary, they can take a serious toll on your body.
The focus of my exercise, training and nutrition approach is to keep my body healthy in order that my body can “endure” such events, not only now, but long into the future.
Deviating slightly from the topic, I’d recommend that unless you are a professional athlete, reducing your training volume, and including more short duration, high intensity work along with a minimalist strength training routine is the most sensible option to stay healthy in the long run.
From a dietary perspective I’d recommend doing the bulk of your training in either the fasted state, or a carbohydrate depleted state as this has been shown to both help burn body fat (the less bodyfat you have, the better your power to weight ratio), and increase your body’s efficiency at burning fat during an event, thus preserving carbohydrate stores for when you really need them.3
When it comes to actual race day performance, there is little question in the scientific literature that for endurance events of marathon distance or longer, carb intake is important, both in the days preceding the race, and during the event itself.4,5
That said, not all carbs are created equal, so choosing which foods and supplements one fuels one’s body with can make a huge difference to one’s performance and long term health.
Optimal Carb Loading
Pasta is an old carb-loading favourite of many endurance athletes, however it may well be an ill advised choice for many for a number of reasons:
1) You may be an undiagnosed celiac. It’s relatively unlikely, maybe 1-3 in 100, but certainly possible. Famously tennis star Novak Djokovic made great leaps in performance after discovering he had the condition. Even if you’re not celiac, it is thought around 6% of people suffer from wheat allergy and approximately another 6% from gluten-sensitivity. All in all that’s potentially 1 in 6 people who will benefit tremendously from avoiding the ubiquitous grain!6
2) Digestive distress. Wheat is high in oligosaccharides which are fermented by bacteria living in the gut. If you have an overgrowth of these bacteria in the small intestine, or the wrong kinds of microbes this can lead to the symptoms of IBS. Not what you want if you’re trying to carb load or take part in an endurance event!
If not pasta, then what should one carb load with? The following is my carb loading continuum, from best, to worst:
1) White Rice (or even rice pudding)
Low in indigestible fibre, anti-nutrients and toxins, white rice is essentially pure glucose. It’s very easy to digest, won’t bloat you or cause inflammation. The sugar in the rice pudding will add extra carbs, and the fructose will help fill the hepatic glycogen stores in the liver.
2) Starchy Root Vegetables (peeled)
White potatoes, sweet potatoes, yams etc. Make sure they’re well cooked, and consider mashing them to aid digestion further.
3) Sports drinks/Glucose solution
Research shows that to really improve performance athletes should take on up to 7g of carbohydrate per kg of bodyweight per day in the 2-3 days leading up to an endurance event of marathon distance or longer. This equates to an awful lot of food! Drinking a solution of glucose or 3:1 glucose:fructose solution along with your meals can make it easier to reach your target carb consumption without exploding!
4) Oats and other alternative grains
Oats and some other grains such as rye and spelt may be a better choice than wheat, particularly if soaked, sprouted and fermented properly first. Though perhaps not as good physiologically as the above, they can add some variety and taste to your pre-race diet. You’re not a robot after all! It could still be worth going 100% grain free for at least 30 days however, and seeing what effect this has on your performance, and then what happens when they’re reintroduced.
5) Legumes
As above, except these tend to be even more filling, and thus make it hard to consume enough calories/carbs.
6) Fruits and vegetables
Though these should comprise the majority of the bulk of your diet under normal circumstances, the high fiber content makes them very filling, and therefore not a good choice if your aim is to take on as much energy in the form of carbohydrate as possible! They are a bad choice for carb loading for exactly the reason they are a good choice for weight loss.
Race Day Nutrition
Despite the misleading title, this study indicates that, providing you have carb-loaded in the days preceding the race, it makes no difference whether you have a high fat or high carb breakfast.7
My recommendation for pre-race breakfast is to eat a meal you enjoy, have tested before, and know won’t cause you digestive distress.
In terms of in race nutrition, as distance increases, the more carbs you can ingest, the better you’re likely to do. A recent study suggests that taking on as much as 48-78g of carbs per hour produces optimal performance, with the caveat that this is only if you can stomach it!8
As glucose, maltodextrin and fructose are all absorbed via different pathways, finding a product that is a blend of all three should produce the best results.
Why am I doing all this?
Just a call to remember to ask yourself why you’re doing all this again.
No matter what the distance, the fact is if you’re well trained, and used to eating a healthy whole foods diet, you should be able to complete the distance with no carbs whatsoever.
Carb loading and using sports drinks and gels may help you do it faster but this is really only proven in high level athletes. It could be worth asking yourself if stuffing yourself silly for 3 days, then spending a fortune on disgusting tasting carb gels and drinks during your event is really worth it?
Personally I just eat some tasty rice and potato dishes in the days preceding the race to satiety, have a bowl of porridge, raisins and honey in the morning because I enjoy the taste, and take some dates, dried bananas and NAKD bars out the event with me because I like them!
1. http://www.nutritionandmetabolism.com/content/9/1/32
2. http://wholehealthsource.blogspot.co.uk/2011/08/carbohydrate-hypothesis-of-obesity.html
3. http://www.ncbi.nlm.nih.gov/pubmed/22805754
4. http://www.ncbi.nlm.nih.gov/pubmed/21590642
5. http://sweatscience.com/the-more-you-eat-the-faster-you-go-in-ultraendurance/
6. http://www.biomedcentral.com/1741-7015/10/13
7. http://www.ncbi.nlm.nih.gov/pubmed/22852054?dopt=Abstract
8. http://sweatscience.runnersworld.com/2012/10/the-optimal-carbohydrate-dose-for-endurance/
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