As with all sports, when practising winter sports we also consume a certain amount of energy that we otherwise wouldn't expend. Therefore, it's important to maintain some control and know how to act accordingly.
Do you know the differences between carbohydrates, fats and proteins?
There are slight variations in these equivalents depending on the type of energy macronutrient (carbohydrates, fats or proteins) being used. Thus, using one litre of oxygen to metabolise only fats generates 4.48 kcal (19.59kj); consuming one litre of oxygen for protein metabolism equates to 4.48 kcal (18.75 kj), while metabolising glycogen gives an equivalent of 5.06 kcal (21.18 kj). To simplify calculations, it's accepted that consuming one litre of oxygen, regardless of the fuel source used, equals 5 kcal (20.90 kj).
Energy expenditure... kcal, kj or METs?
Energy expenditure associated with an activity can also be expressed in kcal, kj or METs. METs are used to express energy expenditure, where one MET equals oxygen consumption of 3.5 ml per kilogram per minute - it's estimated that an adult's resting expenditure equals one MET. The number of METs consumed by a particular physical activity can be expressed. The table below describes the energy cost associated with different physical activities and/or snow sports.
Energy expenditure is high in all winter activities: skiing, cross-country skiing, snowboarding... some authors describe that the total daily energy expenditure for cross-country skiers ranges between 4,800 and 6,000 kcal during most of the season, which includes two daily training sessions. In cross-country skiing, the energy expenditure consumed over distances of 15 km and 50 km has been estimated at 950-1,200 kcal and 3,100-3,600 kcal respectively.
Energy balance
This can be estimated through surveys or measured by weighing food consumption (energy intake) while simultaneously estimating daily energy expenditure including that associated with physical activity. In this way, we can analyse the energy balance or relationship between energy intake and expenditure.
When the balance is negative, the athlete needs to mobilise their energy reserves (triglycerides or fat from adipose tissue) to compensate for energy expenditure. When the balance is positive, energy intake exceeds expenditure, and the unused energy is stored as fat in adipose tissue.
However, increased body fat is significantly influenced by the quantitative composition of the diet - when excess energy is consumed as fat, it's much more likely to be stored as fat than when consuming excess carbohydrates or proteins. Within the carbohydrate group, those that lead to rapid insulin secretion (fast-absorbing carbohydrates) are more likely to be stored as fat, as this hormone stimulates lipid synthesis (lipogenic hormone).
Changes in body weight may not indicate this balance, particularly in athletes, as increased muscle mass associated with strength or power training could mask a reduction in body fat. As muscle tissue has greater density than adipose tissue, the same volume weighs more; therefore, even when in energy balance, weight gain associated with changes in body composition is possible.
Now that we've explained energy expenditure in more detail, you'll be aware of the calories needed to tackle a big day on the slopes.
