Your Marathon Training Diet

Your marathon training diet should be focussed on consuming quality carbs at the right times! With all of your training, it’s important that your diet is rich in carbs, with a good remaining balance of protein and fats. On a day to day basis throughout the many months of your marathon training program , a good ratio to shoot for is carbs making up 65% of your daily caloric intake with proteins closer to 20% and fat making up the remaining 15%. During pre-marathon week, your carb intake can increase to 75% as you aim to top off your newly-enlarged glycogen storage tanks to go the distance!

Having said that, the two biggest questions remain:

Why Carbs and What Kinds of Carbs?

Why Carbs are King for Endurance Training

In order to properly understand what foods constitute a good marathon training diet, let’s examine the purpose of endurance training in order to properly prepare you for the vigours of the marathon.

As you likely know, when training for a marathon, the long run (on this website defined as anything farther than 15 miles) is the most important running workout in your program. These long runs provide a long list of training benefits including the stimulation and development of slow twitch muscle fibres, mitochondria development and on the topic of a good marathon training diet, of particular importance is ‘glycogen sparing’.

While running, your body always uses a balanced combination of body fat and glycogen (converted sugar stored in your muscles, liver and blood) as sources for fuel energy. As you increase your running pace , your body shifts to using a higher percentage of glycogen than fat since fat needs an abundance of oxygen to burn to produce energy. While we all have enough energy in the form of body fat to literally run for days on end, our body also needs the glycogen for proper brain and muscle performance. The challenge is that glycogen stores are limited. In fact, glycogen stores and your body’s ability to use them sparingly is probably the single most important success factor for marathoners.

Concerning how much fat and how much glycogen to burn during running, training for many continuous hours invokes two important physiological responses. The first response is that your body learns to conserve your glycogen by burning a higher ratio of fat while running. The second response is the size or storage capacity of your glycogen stores increase.

Specifically, your muscle stores can be trained to increase by 50%! This adaptation is basically what protects you from ‘hitting the wall’ or running out of muscle glycogen. It’s this very training adaptation that requires you to pay attention to the quality, quantity and timing of the food that you consume.

Which Carbs are Best?

Not all carbs are equal. For runners and non-runners alike it’s generally wise to pursue carbs that score low on what’s known as the ‘glycemic index’. The glycemic index rates carbohydrates according to their effect on our blood glucose levels. Lower GI foods produce smaller fluctuations in blood glucose and insulin levels. This results in a more stable and sustainable energy supply.

In general low glycemic foods consist of high fibre, unrefined breads made with whole grains or stone-ground flour, cereals consisting of oats, barley and/or brans, most fruits and vegetables, pasta, noodles. One thing to note is, like the individual training response, the glycemic response is that is does vary person to person and also is affected by the way the food has been prepared. For example, a boiled potato has a lower glycemic index than a baked potato.

For a complete but simple low down on the whole glycemic index eating strategy to get your marathon training diet right, including lists of foods and recipes, check out the following two great reads:



Marathon Training Diet Summary

  1. Aim for 65% of your daily caloric intake to be from good quality carbs. Up it to 75% during the week before your marathon.
  2. Hitting the wall is depletion of muscle glycogen. Marathon training long runs protect you from this by causing adaptations that result in increased muscle glycogen storage – as much as 50% more!
  3. Lower glycemic foods provide more sustainable energy for endurance exercise – they enable to you last longer before your glycogen stores deplete.
  4. Runners benefit from higher glycemic carbs during the first few hours after running workouts as they quickly replenish glycogen stores for a speedy recovery.

*For much more information on how the timing and frequency of eating and nutrition for runners in general, check out the nutrition for runners page.

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