Eating a particularly large breakfast on the morning of a cycling marathon is not advisable. That is the brief conclusion of a study. Twelve trained cyclists took part in the study conducted by Maastricht University. The researchers wanted to find out whether breakfast on the day of the race still plays a role in replenishing glycogen stores once those stores have already been well filled. They used magnetic resonance spectroscopy to measure glycogen concentrations in the muscles and liver. Breakfast consisted of orange juice, white bread, raisin bread and jam, with a total fructose content of 25 per cent. The participants abstained from exercise and alcohol for two days prior to the test. On the evening before, they consumed a standardised meal consisting of 65 per cent carbohydrates, 20 per cent fat and 15 per cent protein.
Carb-loading at breakfast?
The carbohydrates consumed were distributed across various metabolic pathways. Some remained in the stomach, whilst other portions reached the liver but had not yet been converted into glycogen. The participants in the study had high baseline levels of stored muscle glycogen, which were close to the maximum for trained endurance athletes. For breakfast, they consumed 3 g of carbohydrates per kg of body weight. They then waited three hours before the measurements were taken. No significant change was observed in the glycogen stored in the muscles. Similarly, no significant benefit was evident in the glycogen stored in the liver (although there was slightly more glycogen, there was a slight reduction in liver size). The researchers conclude that anyone who has already replenished their stores in the days leading up to the event gains no further benefit on the morning of the competition. They can therefore do without a high intake of carbohydrates (3 g per kg of body weight). A light breakfast in smaller quantities is perfectly sufficient.
How carboloading works
Carboloading involves deliberately consuming very large amounts of carbohydrates in the days leading up to an endurance competition. The body converts these carbohydrates into glycogen and stores it as an energy reserve. Glycogen is stored primarily in two ‘depots’: in the muscles and in the liver. The fuller these stores are before the competition, the longer the body can draw on readily available energy before it has to switch to the slower process of burning fat. However, there is no point in eating large quantities without a plan – it’s all about the type of food. The aim is to consume less protein and fat and, instead, to eat more carbohydrate-rich foods.
Avoiding wholemeal
Many nutrition experts also recommend avoiding wholemeal products when carb-loading. They put more strain on the stomach, and large amounts of fibre also bind a lot of water, thereby increasing body weight. Glycogen already binds a lot of water and leads to a higher body weight – adding plenty of fibre would make this effect even more pronounced.
