Nutrition during the Tour du Mont Blanc: how to eat more to finish faster!
Everyone has a story from the Tour du Mont Blanc! Here’s one of ours (name changed to protect the guilty):
The first part of the ride had gone extremely well, and John was feeling good as he approached the col du Petit Saint Bernard. He made most of the climb together with another rider, not talking much but enjoying each other’s company as they passed first one, then two and finally a third competitor, leaving them well behind as they reached the feed station. Curious to know where they stood, he asked the feed station attendant.
‘How many are in front of us?’
‘Oh, not many! Maybe ten?’
John was so excited by this that like a U23 rider in his first race he immediately dropped what he was eating, jumped back on the bike and launched into a fast and furious descent. He caught and overtook someone on the descent, skipped the feed station and Bourg St Maurice and then caught two more people on the early slopes of the Cormet de Roselend. He was now either sixth or seventh! Pushing on as fast as he could, he crossed the penultimate summit and made another fast descent to Beaufort and the foot of the final climb.
There’s an abrupt change in rhythm when you turn off to Hauteluce and Les Saisies, and the slope is punishingly steep for a few hundred metres. This is always a shock to the system, and John could feel his strength ebbing away. Nevertheless, he was still confident and kept pushing. Only a few kilometres left!
It happened without warning. In his own words, ‘the man with the hammer suddenly jumped out at me, and BOOM!’ John came to a complete stop, totally incapable of pedalling another centimetre. He fell off his bike and lay down by the side of the road, feeling utterly exhausted. Soon one rider, then another, came up and passed him, each enquiring if he was OK. Fifteen minutes or more passed before John remembered he had a gel in his back pocket. It took an effort to get it out and suck it down. Slowly, some energy returned and after an eternity John was finally able to get back on the bike and pedal painfully up the remaining eight or nine kilometres to the finish, where he learned he was 17th.
All the riders he had passed since the col du Petit Saint Bernard overtook him again on the final climb and finished in front of him. He looks back on the day now and says, wryly, ‘I was a complete idiot! Failing to eat properly in the last third of the race cost me 45 minutes and a top ten place.’
The story underlines that nutrition (including, of course, hydration) during long endurance events is a vital part of a successful ride. If, like John, you have experienced a severe “bonk” while out on a long ride, you will know what we are talking about!
The thing about the Tour du Mont Blanc is, whether you expect to finish with the leaders in 12 hours or to just make it in time before the 19 hour cut-off, you cannot hope to use the same nutrition strategy that you would use on a typical sportive. It’s possible to have a successful ride at the Etape du Tour or even the Marmotte using only energy drinks, gels and bars. This has no chance of working at the TMB, where not only you must eat considerably more, but also you need a much wider variety of solid food, including savouries.
Your primary challenge with nutrition and hydration during the event is to ensure you always have enough energy to fuel your expenditure. For anyone interested in pushing their limits, this is not as easy as it sounds. Let’s take a look at the issues.
First, the sources. Your body essentially runs on two different sorts of fuel: fat and carbohydrate (it is true that protein can also be used as a fuel but this happens only under extreme conditions). You have an essentially unlimited store of fat, but no more than 2,000 kcal worth of carbohydrate (stored as glycogen, some of which is irrelevant because stored in muscles that aren’t used for cycling).
Your energy expenditure during the TMB will be in the range of 10,000 – 12,000 kcal, so obviously your stock of glycogen will soon run out. So where is the energy going to come from? Research1 has shown that highly trained athletes can burn a mix of up to 50% fat/50% carbohydrate (CHO) at fast endurance pace, so in the best case, you could get 5-6,000 kcal from your fat stores and need to supply the rest during the event. Note that the ability to burn fat drops off rapidly to zero at higher intensities, underlying the importance of keeping a steady, moderate pace.
It has been shown2 that athletes can benefit from consuming up to as much as 120g of CHO per hour, equivalent to 480 kcal. A typical rider, taking 16h to complete the tour, could thus theoretically consume about 7,700 kcal.
In practice this is hard to achieve, for two reasons. First, the 120g upper limit is believed to be feasible only with a 2:1 ratio of glucose and fructose (which have different pathways for digestion). A typical gel, bar, banana or small sandwich contains 25-30g CHO, but not always in the right ratio. A 500ml bottle of energy drink contains about the same amount. To achieve 120g/hr you would thus need to consume, hour after hour, at least three food items (gels, bars, bananas, sandwiches, etc.) plus a bottle of energy drink, while respecting the 2:1 glucose/fructose ratio.
Second, consuming this amount while cycling at a sustained pace is not easy, requires a conscious effort, and may result in gastric distress.
A hypothetical rider expending 12,000kcal, able to get 50% of her energy needs at endurance pace by burning fat, would thus need to consume 6,000kcal. This works out to 94g of CHO per hour throughout the event. It leaves little margin for error: pushing too hard for 20-30 minutes or forgetting to eat for the same period could tip her over the edge.
These calculations underline the importance of two things during training for the TMB:
- Train to become a better “fat-burner”
- Train your gut to be comfortable dealing with at least 100g of CHO per hour, and 120g if possible.
Read our previous article for more on nutrition during your training for the TMB.
Even if you are not interested in pushing hard, and just want to finish inside the time limit, it is still important to improve your fat-burning capacity and become comfortable with consuming at least 100g of CHO per hour. Your margin for error will be wider than for someone who is really going for it, but the risk of running out of energy is still very much present.
Let’s look now at how to get it right on the day.
The last few days
Getting it right on the day starts three to four days prior to the event. The key things to do in the last few days are:
- Increase the proportion of CHO in your diet
- Decrease the amount of fibre
- Stay fully hydrated
The purpose of eating more CHO is to ensure that you start with your glycogen stores fully topped up. This is not a reason to eat more calories, however, so take care to reduce the fat by a corresponding amount and perhaps limit the protein as well. In practical terms this means increasing the amount of foods such as bread, rice, potatoes or pasta while reducing or eliminating foods with high fat content, such as whole milk, butter, cheese, ice cream, oils, avocados, nuts and fatty cuts of meats or oily fish such as mackerel and sardines.
It’s also advisable to choose food that is relatively low in fibre in order for your digestive tract to be as empty as possible on the start line. Avoid such things as chia seeds, avocados, almonds, pistachios, berries, broccoli, asparagus, aubergines and anything made from wholemeal grains. For the last couple of days, it is best to go for white bread, white rice or ordinary pasta rather than the wholemeal versions.
Staying fully hydrated should be a no-brainer but can be challenging if the weather is hot and you are travelling. There’s no need to drink litres and litres of water; just make sure you are urinating regularly and that the colour is clear.
Race day supplies
The first question before considering race day supplies is: will you be supported or unsupported? There’s absolutely no need to be supported and many riders consider it a “purer” way to ride the event. Nevertheless, there are certain advantages to being supported. One of these is the ability to control exactly what you have available to eat and drink, thus reducing the risk of consuming something that doesn’t agree with you.
Assuming you are unsupported, you will still need your own supplies to complement what is provided by the race organisation (if nothing else to cover the 54km from the start to the first feed station). You should also test in advance most or all of the items on the feed station “menus” to ensure they work for you in hot weather and under stressful conditions.
The sports nutrition partner for 2021 is 6D Sports Nutrition so you can expect to see many of their products, including their Isotonic Sports Drink, gels and energy bars. If you are not familiar with these products we strongly recommend you purchase and test a few in advance. This is not a commercial plug, just common sense advice.
In addition to the afore-mentioned sports nutrition products, the event organisation has told us that there will be an array of everyday food available at all the feed stations, including both sweet and savoury biscuits, crisps, bananas, dried fruit and fruit purée, and extras as follows:
- Grand Saint Bernard: cold cuts (ham and sausage)
- La Salle: hot pasta, hot soup and hot tea
- Petit Saint Bernard: cold cuts (ham and sausage) and hot tea
- Bourg Saint Maurice: hot pasta, hot soup, hot tea and Beaufort cheese
- Cormet de Roselend: hot tea
The soup and pasta at La Salle (218km) and Bourg Saint Maurice (284km) are particularly appreciated and give a welcome break from sweet energy bars and the like!
Bearing in mind the goal of consuming at least 100g/hour of CHO, the question becomes how to mix it? Here are some of the factors to take into account:
- How many calories to drink? It’s hard to eat solid food while climbing so drinking as many calories as possible is a good strategy. Anything more than 30g per 500ml bottle, however, is likely to taste too sweet and lead you to reject it after the first few hours.
- A typical energy bar contains 25-30g of CHO. They are, however, highly dehydrated so you must drink plenty of water at the same time.
- After the first few hours you will start craving variety and different tastes, especially savouries and real food. Wraps, sandwiches and rice cakes are all excellent choices. The book Feed Zone Portables3 by Biju Thomas and Allen Lim is a remarkable source of ideas and simple recipes, although there’s only so much you can carry.
- In case you start to feel sick after too many sweet items, there’s some evidence that consuming ginger and/or artichoke extracts may help keep your stomach settled4,5.
The name of the day is ‘carbs, carbs and more carbs, with a bit of protein’. It begins with breakfast, which will necessarily be very early, considering the 5am start. This is not the time for innovation so make sure you have thoroughly tested your breakfast before your training rides in the weeks before the event. You should eat something you like that is high in CHO and low in fibre, such as cornflakes, white rice, honey sandwiches made with white bread and perhaps some low-fibre fruit such as melon or fruit juice (without pulp).
Avoid taking a gel 15min or so before the start: this will only create an unwanted insulin spike. Prefer, rather, something slower-acting such as a couple of dried apricots or a banana (keep the gel for the false flat through Praz-sur-Arly and Megève, just after the initial descent).
From the moment you cross the start line and until the finish you should aim at consuming at least one 500ml bottle of isotonic energy drink and three food items per hour. It’s worth setting an alarm on your bike computer to remind you to eat something every 15-20 minutes. Bear in mind that you will use considerably more energy on the climbs than on the descents, so prepare for the next climb by eating (whenever safe) on the preceding descent.
Refer to the table below for a nutrition plan based on taking 16 hours to finish. It suggests a total consumption of 1,910g of CHO, which represents about 7,600 kcal. Remember that depending on your body weight and your metabolic efficiency you should expect to expend some 10-12,000 kcal so there remains a substantial deficit, which needs to be made up by burning fat (and some glycogen) from your body’s internal reserves.
It should be obvious that nutrition is as important as physical and mental fitness for a successful ride at the TMB. Practice your nutrition strategy during your long training rides and test the available options so that you know what works for you.
For more on optimum nutrition during your training, how to achieve your target body-weight and how to become a more efficient fat-burner, read our previous article: Become a lean, mean, fat-burning machine!
- Goedecke, Julia et al. (2001). Determinants of the variability in respiratory exchange ratio at rest and during exercise in trained athletes. AJP Endocrinology and metabolism. 279. E1325-34. 10.1152/ajpendo.2000.279.6.E1325.
- https://www.mysportscience.com/post/120-grams-per-hourand https://www.mysportscience.com/post/the-case-for-high-carbohydrate-intake-during-long-races
- Thomas, Biju & Lim, Allen. (2013). Feed Zone Portables: a cookbook of on-the-go food for athletes. Velopress, Boulder CO.
- Drobnic, Franchek et al. (2020). A pilot study on the efficacy of a rational combination of artichoke and ginger extracts with simethicone in the treatment of gastrointestinal symptoms in endurance athletes. Minerva gastroenterologica e dietologica. 10.23736/S1121-421X.20.02664-1.
- Ball, Derek et al (2015). Exercise-induced gastrointestinal disturbances: potential amelioration with a ginger containing beverage. Proceedings of the Nutrition Society. 74. 10.1017/S0029665115002128.