A good diet filled with the right nutrients is an essential part of any exercise routine, but it’s especially important for endurance events like marathons or triathlons. Our ability to run, bicycle, swim and ski builds on the capacity of the body to extract energy from ingested food.
A nutrition plan better to start at least a few weeks before the event. Low GI carbohydrates such as wholegrain rice and pasta are good to introduce into a general diet at this stage, as they release energy slowly and will build up body’s carbohydrate resources. Carbohydrate is considered the body’s most efficient fuel source because it requires less oxygen to burn in comparison with protein or fat during high-intensity exercise, when the body cannot process enough oxygen to meet its needs.
However, recently some experts have suggested a low-carbohydrate diet is better than a high-carb, arguing when runners maintain a low-carb diet their muscles become better fat burners, an adaptation that spare muscle glycogen in marathons. Studies have shown that low-carb diets do indeed increase fat burning during running. Yet, this effect has not been linked to improved endurance performance. Meanwhile, new research has reconfirmed that runners aren’t able to train as hard on a low-carb diet because it produces chronically low glycogen stores.
In addition to the diet, complicating matters for runners is something called the compensation effect. The more we train, the more our appetite increases and the more we eat. Simply ignoring the increased appetite is not a viable solution, but neither is an extra-large, double-cheese pizza. Instead, runners must increase the quality of their diets. High-quality foods such as vegetables are less calorically dense than low-quality foods, satisfying the appetite with fewer calories. The six high-quality food types are vegetables, fruits, nuts and seeds, whole grains, lean meats and fish, and dairy.
The final week before an event is the time for real carb-loading like pasta and porridge. A few hours before any long run, eat a meal high in low GI carbohydrates, moderate in protein and low in fat, to give a body all the nutrients it needs for the next few hours. Porridge with fruits, a chicken sandwich and fruit or a bagel and peanut butter are good options. Be wary of gas-inducing carbs, though, such as cabbage, broccoli, beans or too much fruit, or it could make for an uncomfortable run!
During long runs is important to refill body’s carbohydrate stores after 90 minutes or more. The body can only store around 2,000 kcals of glycogen and after a few hours of running, you can ‘hit the wall’ when the body’s carbohydrate reserve gets low and the brain and muscles show signs of fatigue. Take some high GI carbohydrate food every 45-60 minutes during a long run (around 30-60 grams of per hour). Choose specially designed sport gels and isotonic drinks, or try bananas, oranges, honey, dried fruit or gummy sweets such as jelly beans and don’t forget to stay hydrated with plenty of fluids and electrolytes.
The amount of carbohydrate a runner needs to handle his or her training is tied to the amount of training he or she does. Use this table to determine how much carbohydrate to include in your diet.
Average Daily Training Time (Running and Other Activities) Daily Carbohydrate Target
30-45 minutes 3-4 g/kg
46-60 minutes 4-5 g/kg
61-75 minutes 5-6 g/kg
76-90 minutes 6-7 g/kg
90 minutes 7-8 g/kg
>120 minutes 8-10 g/kg
After long runs are two optimal windows of recovery following a hard workout that play crucial roles in helping your body recover as quickly as possible. The best nutrients to consume during the 30 minute window soon after prolonged exercise, is a mix of carbohydrates and protein. You should aim to consume 100-300 calories. The ratio of carbohydrates to protein should be 3:1 or 4:1 (carbohydrates: protein). This combination of carbohydrates to protein helps the body re-synthesis muscle glycogen more efficiently than carbohydrates alone.
The second window for optimal recovery is from one hour to three hours post workout. In this window of recovery, a meal or snack that is higher in protein, but also includes a healthy fat and carbohydrate is best. This can consist of 150 calories and up. The goal with eating in these two windows is not to consume more calories than you actually need; rather, the purpose is to give your body the right combination of nutrients at the right time, decrease inflammation, increase muscle glycogen stores, and rebuild damaged muscle tissue.
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 T. Noakes, J. Volek, S. Phinney Low-carbohydrate diets for athletes: what evidence?: British Journal of Sports Medicine, 2014.