Friday, December 31, 2010

Carbohydrate Loading - More than just a bowl of pasta

In the last post we looked at the need to begin endurance exercise with the maximum possible level of stored carbohydrate if we want to maximise performance. In exercise of over 2 hours, studies show a performance benefit of around 8% with complete carbohydrate loading compared to only partially loaded stores. For so many sportspeople I’ve met, their idea of carb loading is simply eating a big bowl of pasta the night before a race. But what you’ll see here is that it’s much more than that.


Carb Loading Starts 2 days before the event
Preparation for an endurance event needs to begin 2 days beforehand. At this time it is best to minimise the amount of training if possible in order to store vital glycogen, the body’s storage form of carbohydrate. Training during this time uses up carbohydrate and is essentially undoing much of that hard work (ie. eating).
Carbohydrate loading is the process of eating to store the maximum amount of carbohydrate in your muscles and liver, which can then be used during endurance exercise. It requires a massive amount of carbohydrate to be eaten in those two days.
Having worked with a large number of cyclists, runners, adventure racers and ironman triathletes, it’s obvious that most people have little concept of exactly how much carbohydrate needs to be eaten to properly carb load. I’ve conducted studie whereby the athletes recorded everything they ate for the two days prior to a half ironman triathlon. I then analysed their diets and compared the amount of carbs they actually ate to what they ideally needed. The results certainly shocked me: in the first study only one of the 16 athletes adequately carb loaded, and five of them didn’t even achieve 50% of their required carbohydrate quantity!

You need a LOT of carbs to carb load
The one aspect of carb loading that shocks most people is the amount of carbs required to do it properly. It’s 8-12 grams of carbs for every kilogram of body weight, depending on factors such as gender, level of body fat, and if you’re trying to win or just finish.
To calculate this amount of carbs for example, an 80kg athlete eating 10g per kg would need 10 X 80 = 800 grams of carbohydrate a day for the two days beforehand.  To put that in perspective one slice of bread contains 15 grams, one cup of cooked pasta gives you 35 grams and 1 litre of soft drink or cordial has 120 grams!
Sources of carbohydrate include breakfast cereals, bread, fruit and juice, pasta, rice, starchy vegetables, low fat yoghurt and flavoured milk, sugar, lollies, soft drinks and sports drinks, and should be the focus of meals and snacks. Avoid foods high in fat such as take-away, fried foods, chocolate and high fat snacks as these will not help fuel up and will get in the way of the large amount of carbohydrate needed to be eaten.
Because you need such a large amount of food to properly carb load, more processed varieties are actually better because they’re less filling. White bread, jam and honey, lollies, Rice Bubbles, and sugar containing fluids like juice, cordial and soft drink all good choices, as they provide a lot of carbs without being too filling.
One thing I can’t emphasise enough is that in the two or three days before the first day of an event everything that goes in your mouth needs to be specifically chosen because it’s high in carbs and low in fat. Eating large amounts of protein foods (meat, fish, chicken, eggs, nuts) or fatty foods is very filling, and you will then struggle to get enough carbs in.

Do you need 8g/kg or 12g/kg?
As mentioned earlier, there’s a range of carbohydrate amounts to be eaten to carb load. This will depend on:
·         Gender: women generally cannot store as much carbohydrate for the same body weight as men, but also use less during exercise
·         Body fat: leaner athletes have a higher percentage of muscle of their total body weight compared to athletes carrying more body fat
·         Level of competitiveness:  If you’re entering an event just to finish you may not be concerned with absolutely maximising performance. Therefore carbohydrate stores are less critical to you
The picture below gives you a feel for when to eat to the higher or lower end of the spectrum.


Recommended range for carbohydrate to eat when carb loading

Example
To finish off, let’s look at how this translates into food for one particular athlete. This was a 45 year old male Ironman triathlete, Steve, who I first worked with at a half Ironman event. He finished the event in 4hr 47min, in the top 25% of his age group. At this race I measured the amount of carbs he ate in the two days prior. He was fairly lean and weighed 75kg, was aiming to do well in his age group and was preparing for a full Ironman distance later that year.
At the Half Ironman Steve did not eat sufficient carbohydrate to maximise his performance, eating an average of only 396 grams of carbs a day over the two days prior. To put that into perspective, that’s 396/75 = 5.3 grams per kg body weight per day, far below the recommended 8-12 grams per kg per day!
Steve’s diet the two days before the Half Ironman contained mostly carbohydrate containing foods, but nowhere near enough. He was also eating around 30g of fibre which is a normal daily amount, but this would be a problem if we simply increased the quantities of the foods he was already eating, because his fibre intake would increase and make it difficult to tolerate the quantity of food required. He was also eating large amounts of both protein and fat on these days, which would also make it very difficult to increase the amount of food eaten as both protein and fat are very filling.
A few weeks later Steve came to see me in the clinic. We decided that given he was completing a full distance Ironman triathlon, was quite lean and wanted to be competitive in his age group, he would attempt to eat 12 grams per kg per day for the two days prior to the next race. For Steve that’s 12 X 75 = 900g of carbohydrate, a LOT more than the 396g he managed at the last event!
Finally we decided to start with a clean slate when designing Steve’s carb loading plan, given that his strategy to date was so far from what he wanted to achieve. We discussed a range of high carb and low protein, fat and fibre options. Eventually we constructed the following plan:
Breakfast
2 cups Corn Flakes or Nutri Grain with 1 cup of milk
2 slice fruit toast/bread with 3 teaspoons of jam or honey on each
400mL orange juice

Morning Snack
2 hot cross buns with 2 teaspoons jam or honey on each
500mL bottle of juice/soft drink/cordial (normal dilution) over the morning

Lunch
2 cups cooked rice (2/3 cup when raw) with meat or chicken/veggies/sauce of your choice
1 cereal bar (eg. K-Time or Uncle Toby’s Fruit Twist)
600mL juice/soft drink/cordial

Afternoon Snack
2 sandwiches (4 slices white bread) with 3 teaspoons of jam in each (or more)
300mL juice/soft drink/cordial

Dinner
2 ½ cups cooked pasta (1 cup dry) with fish/meat/chicken and sauce of your choice
600mL juice/soft drink/cordial

Dessert
3 medium/large pancakes (from packet mix) with 1 banana and 3 tablespoons maple syrup

After Dinner
200g tub low fat fruit flavoured yoghurt

This plan provided Steve with 912g per day of carbohydrate, just over 12g per kg (900g). Importantly it only contained 61g of fat, 32g of fibre and 125g of protein. Steve trialled it prior to a couple of long weekend training sessions and found that whilst he performed better in the session, he was still struggling to eat the required quantity of food. To overcome this, we changed some of the bulkier snacks (eg. pancakes and hot cross buns) to lollies to reduce the protein and fibre content. Steve found this easier and came close to eating the entire meal plan prior to the full distance Ironman, where he finished with a personal best over the distance.

Summary
Starting an endurance event (distance over 2 hours) completely carbohydrate loaded will give you a significant advantage for that event compared with not properly carb loading. Most athletes have a rough idea of what carb loading is, but appear to have little understanding of just how much food they need to eat. To carb load properly, aim to eat 8-12 grams per kg of body weight per day for the two days prior to an event. If you struggle to eat the large amount of food required to achieve this, choose foods that are high in carbs but low in fibre, protein and fat. These foods include white bread, low fibre, sugary breakfast cereals, lollies, cordial, juice and soft drink. As a final note, remember never to try carb loading like this (or any other new strategy) for the first time in a race. ALWAYS try new things in training first, to make sure you’re not in for any nasty surprises.
So having now covered eating before endurance sports, in the next post I’ll look at the issue of eating carbohydrate during endurance events, and some interesting new research that is changing the way we approach this. For now have a great new year and enjoy your sport!


12 comments:

  1. Are there studies that look at carb loading in athletes who are fed reasonable amounts of CHO during exercise as well? Or do most studies have no supplementary CHO during exercise?

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  2. My apologies for the horrifically late reply - I only just realised I didn't have email alerts on for comments and a few have banked up unchecked!

    To answer your question there's three quite good studies on this - two did not allow any carbohydrate during exercise, but in the other the participants consumed 60g an hour of carbs during the initial 2hr "steady state", but just water during the 1hr time trial that followed.

    There's really not much research out there that puts together all of the strategies that an athlete has in his arsenal (carbs before and during exercise, fluid, caffeine, buffers, nitrates, etc.) to look at the benefit of all factors put together. So we don't really know if the effects are additive, synergistic or not as great as they appear individually.

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  3. Hi there,

    I like the articles. I've got a silly question, how many grams in a cup?
    2 Cups of Nutrigrain = XX grams of Nutrigrain?

    Regards,

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    Replies
    1. Hi Oscar,

      It depends if you want to know how many grams of Nutri-Grain is in a cup, or how many grams of carbohydrate it would contain? Either way there are websites where you can look up this kind of info - www.calorieking.com.au is probably the most complete database in Australia, drop the au for the US equivalent.

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    2. Hi Again,

      I'm just asking on many grams in a cup (not grams of carbs) just
      "2 Cups of Nutrigrain = XX grams of Nutrigrain?"
      2 Cups of Nutrigrain = 60 grams or 80 grams of Nutrigrain?

      Thanks

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    3. No problem, Calorie King lists 2 cups of Nutri Grain as weighing 80g.

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  4. I came to this post from your Sports nutrition strategy article on Cycling Tips. What I struggle with is the focus in so much of the literature on carbs as a fuel source. As endurance athletes, isn't it more relevant to talk about aerobic fitness and hence the importance of training your body to burn fat as its primary fuel source? That's the way to activate your slow twitch fibres. As for loading up on high GI refined and starchy carbs and sugars, doesn't that lead to an increase in insulin which inhibits fat burning thereby negatively impacting the aerobic system?

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  5. Hi there,

    An interesting question. There's a small but increasing body of research (a lot of which comes from RMIT university here in Melbourne) that looks at deliberately starting a training session with minimal carbohydrate stored in the body, and shows benefits to some of the proteins in the muscle that are concerned with using fat as an energy source. But ultimately the only test of significance in the real world is studies measuring performance - and it's been shown that whilst those who do every 2nd training session without much in the way of available carbs do burn more fat during a performance test (after 12 weeks of training like this), they don't perform any better than those doing every training session with maximal carb stores.

    Unfortunately there's no good performance based research that I can find that's ever looked at someone following a low GI or low carb diet for a significant period of time and then also gone low GI before/during a performance trial compared to a traditional high carb approach, so we don't know what that outcome would look like. The reason for this is probably that it's actually very difficult to find athletes willing to be randomised and told to eat either a low carb or moderate-high carb diet for a significant period of time - most people end up falling back into old habits and eating something close to their habitual diet. There's also no good ways of regularly measuring how "compliant" the participants would be with the diet, and no easy way of "blinding" the participants so they didn't know if they were eating low carb or not (to remove any bias when it came to a performance test).

    But we do know that if you eat at least a moderate carb diet normally in training, then a high carb intake the day before and during a race will improve performance, regardless of the GI of the carbohydrate source. This has been shown in studies of carbohydrate loading (usually using high GI carbs to supplement carb intake), plus those looking at the amount of carbs consumed in during exercise.

    The one exception (and this is only a theory held by some people, there's no scientific evidence for or against this) is that high carb intakes may not be necessary in events where the relative exercise intensity is not that high (eg. ultramarathon running that can take 10-30 hours). But certainly in road cycling there's almost always periods of high intensity exercise that will benefit from carbohydrate (hill climbs, sprints, breakaways, etc.).

    Hope that answers you question?

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  6. Hello,
    I have only just found your blog and am a dietitian who a few friends are turning to for help with sports nutrition. As I have next to no experience in this field and we live in an area with limited services, I have been looking for some reputable sources, so am glad I came across your blog.

    Re this post, I am wondering if you are able to provide references for your recommendations, especially the 8-12g/kg advice, as I would be interested in doing some further reading.

    Many thanks.

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    Replies
    1. Apologies for the late reply, I'm on holidays at the moment. Here' a few of the classic studies that look at carbohydrate loading requirements & the effect on performance:

      Glycogen storage capacity: http://www.ncbi.nlm.nih.gov/pubmed/3165600

      Carb loading of glycogen & cycling performance: http://www.ncbi.nlm.nih.gov/pubmed/7749423

      The latest (2002) article looking at how long you need to load for: http://www.ncbi.nlm.nih.gov/pubmed/12111292

      Cheers,

      Alan

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  7. Hi there,

    I have just come across this blog, in an attempt to investigate carbo loading further. Unfortunately, I have left it quite to the last minute to practise implementing this strategy in training; my half ironman race is in a couple of days. As you pointed out, this should not be tried out fully just before a race, however eating enough carbs before the race will still be important for me. Would it be better if I just had some carb-rich lunches and dinners the next couple of days, while just staying low in protein and fat?

    If you don't see this in time, no worries; I will just do something along those lines anyway :)

    A really interesting post, so thank you!

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  8. Hi there,

    How much you attempt to eat for your race will depend partly on how much you eat (and are comfortable/used to eating) on a day-to-day basis already. If a full carb load is not that much more than your usual diet then you could probably do it ok, but if it's a big increase then I'd aim for something in between - maybe 6-7g per kg body weight.

    Good luck for your race!

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