How cold affects carbohydrate metabolism

Exposure to cold increases carbohydrate dependence during exertion. Muscle shivering — including subconscious shivering below the perception threshold — is fueled primarily by carbohydrates. In air below ten degrees Celsius, the rate of carbohydrate oxidation during running is significantly higher than at twenty degrees at the same pace. The carbohydrate requirement per hour is therefore higher in cold conditions than in temperate conditions.

Appetite suppression is milder. Unlike in heat, where appetite is strongly suppressed, cold generally maintains or even increases appetite. This is physiologically beneficial but can create excessive confidence. In cold conditions, athletes may feel they are fueling well because they are hungry and eating, even if carbohydrate intake is insufficient at the right moments.

Peripheral vasoconstriction matters. Cold causes peripheral vasoconstriction to preserve core body temperature, reducing blood flow to the hands and arms. While this does not directly impair gut function as heat does, it can affect fine motor skills — opening packaging, using a mouthpiece, or reaching into a vest pocket become more difficult with cold hands.

The question of viscosity in cold conditions

A common concern with concentrated carbohydrate gels in the cold is that the product becomes too thick to flow. This concern is valid for some products and less well-designed high-concentration formulations. The reason is related to the freezing point.

A high sugar content significantly lowers the freezing point of a solution. This is the same principle that makes ice cream scoopable rather than hard: a high sugar proportion prevents complete crystallization. A concentrated mixture of maltodextrin and fructose with a carbohydrate content of approximately eighty grams per hundred milliliters remains pourable and flowable, even if the ambient temperature drops below freezing.

In practice, between zero and minus five degrees Celsius, the product thickens moderately but remains pourable through a standard mouthpiece. Around minus ten degrees, viscosity further increases, and flow may slow down; keeping the carrier inside the vest, against the body, will keep the product warm enough to flow well. Below minus fifteen degrees, carry the product against your skin or in an insulated pocket. For comparison, isotonic sports drinks and lower-concentration gels carry much more water and become unusable at temperatures that a high-concentration formulation handles without problems.

Carrying strategy in the cold

In cold conditions, the front pockets of a running vest are often underneath other layers — under a windbreaker or shell jacket. Plan accordingly.

The simplest options are to carry the carbohydrate carrier in your hand, allowing hand warmth to keep the product flowing, use a vest with external pockets that extend over a jacket, use an insulated pouch cover in long-term freezing conditions, or pre-warm the carrier at the start of a race by holding it against your body for ten to fifteen minutes before starting.

Hydration in the cold

Runners in the cold consistently drink too little because the sensation of thirst is blunted in cold weather. Cold-weather dehydration is not immediately as symptomatic as in hot weather, but it causes the same performance impairment.

Drink on a schedule in the cold, not according to thirst. Aim for three hundred to five hundred milliliters per hour, depending on intensity and the number of layers. Soft bottles in the front pockets of a vest can freeze in long-term freezing conditions; keep water bottles against your body or use an insulated cover.

Calorie requirements in the cold

Exposure to cold combined with endurance exertion significantly increases total calorie consumption. In environments below five degrees Celsius, total energy requirements can be ten or twenty percent higher than in temperate conditions. Carbohydrate intake targets should reflect this. A runner who typically aims for sixty grams per hour at fifteen degrees might consider sixty-five or seventy grams per hour below five degrees.

Summary

Cold weather increases carbohydrate needs, maintains the flowability of high-concentration gel systems better than low-concentration alternatives, and requires proactive hydration even if thirst is blunted. A high-concentration glucose polymer and fructose formulation is well-suited to Finnish cold-weather conditions. Carry it against your body in severe cold, consider a wider mouthpiece as a backup if a small mouthpiece slows down, and increase hourly intake targets by ten to fifteen percent when competing in prolonged cold.

References

Castellani JW, Young AJ. (2016). Human physiological responses to cold exposure: acute responses and acclimatization to prolonged exposure. Autonomic Neuroscience. 196, 63–74.

Jacobs I, Romet TT, Kerrigan-Brown D. (1985). Muscle glycogen depletion during exercise at 9 degrees C and 21 degrees C. European Journal of Applied Physiology. 54(1), 35–39.

Burke LM, Hawley JA, Wong SHS, Jeukendrup AE. (2011). Carbohydrates for training and competition. Journal of Sports Sciences. 29(Suppl 1), S17–S27.