Fuelling winter endurance events: why you have to think differently in the cold.

Colder weather presents an opportunity for endurance athletes to truly test their limits. The winter months bring unique physiological and nutritional challenges – requiring strategy and advance planning. If you’re tackling a winter ultra or just hoping to get the most out of chilly outdoor training – the right fuelling can be make or break.

Why winter demands are different

Cold and adverse weather increases metabolic demands, above and beyond those already incurred by endurance sport:

• ·Increased energy expenditure: Shivering, thermogenesis (heat production) and maintaining core temperature raise resting metabolic rate (the energy required to meet basic physiological demands at rest) by up to 10–20% (Castellani and Tipton, 2015; Straat et al., 2022).

• Carbohydrates are key: Cold exposure accelerates glycogen use. The body favours carbohydrates for energy, especially when shivering or exercising at higher intensity (Castellani et al., 2016).

• Dehydration risk: Cold reduces thirst sensation by ~40% (Castellani et al., 2016), but fluid losses still occur through sweat, respiration, and dry winter air.

• GI challenges: Cold temperatures can slow gastric emptying, and create barriers to regular fuelling (i.e. gloves, not wanting to stop to get food from packs) – both can increase risk of adverse GI symptoms.

• Practicality: ‘Go-to’ fuel sources may be impractical or unpalatable in colder conditions: frozen gels or solid energy bars make fuelling logistically harder.

• Physiological changes: Drops in body temperature can stimulate feelings of hunger, which increases perceived exertion. Regular fuelling helps prevent this, whilst also promoting thermogenesis (a marginal generation of heat).

Key Considerations

In winter, athletes need to consciously adapt fuelling strategies to offset higher energy expenditure, maintain glycogen stores and hydration.

Carbohydrates: Always a priority – even more so in cold weather.

• Daily recommendation: 6–12 g/kg/day depending on training load.

• During events: Aim for 100-200kcals and 30-60g carbohydrate every 30-45 minutes of activity, scaled by duration and intensity (Jeukendrup, 2014; Naderi et al., 2023).

• Practical tips:

• Use sources that won’t freeze (chews, liquid fuels, gels kept close to body heat). Warm carbohydrate-rich drinks (tea with honey, maltodextrin-based mixes) double as hydration and energy.

Protein:

Protein oxidation rises slightly in cold environments, though less than carbs (Castellani et al., 2016). Aim for marginally higher intake recommendations: 1.6–2.2 g/kg/day to support muscle repair and immune function. Having protein alongside carbohydrates within in-race fuelling options (tested in advance) may reduce muscle breakdown and mitigate hunger levels. Include protein in recovery meals/snacks within 30–60 minutes of finishing cold-weather training.

Fat:

Cold environments slightly increase fat oxidation at low–moderate intensities, but carbs remain king during hard efforts (Castellani et al., 2016). Aim for 20–35% of daily energy intake from healthy fats, focusing on omega-3-rich sources (oily fish, nuts, seeds).

Hydration:

Dehydration remains a risk but can be overlooked in the absence of heat. Cold weather presents unique challenges to hydration:

• Respiratory losses: Breathing cold, dry air increases water loss (Castellani and Tipton, 2015).

• Sweating: Sweat rates may be lower than in summer but sweat trapped under layers of clothing still leads to fluid depletion.

• Blunted thirst: Athletes may underdrink by 20–50% (Castellani et al., 2016).

• Recommendations:

  • Aim for ~0.4–0.8 L/hour during training and racing, depending on intensity and conditions (Cao et al., 2025).

  • Include electrolytes (sodium 300–800 mg/L) to replace losses and maintain fluid balance.

  • Use insulated bottles or hydration packs to prevent freezing. Sip a warm electrolyte drink every 15-20 minutes.

Micronutrients

Endurance athletes training in colder weather may be more susceptible to illness. Key nutrients to prioritise include:

• Vitamin D: Winter sun exposure is often inadequate; deficiency impairs muscle and immune function (UK general population guidance is for supplementation of 400IU daily between September and March. The suggested range for athletes is 1,000-4,000IU daily due to increased musculoskeletal demands.

• Iron: Endurance athletes, especially women, are at risk of deficiency. Deficiency may have an effect on temperature regulation – resulting in feeling more cold.

• Antioxidants (C & E): Support recovery but avoid over-supplementation, which may blunt training adaptations (Naderi et al., 2023).

Practical Fuelling Strategies for longer training and race days

As a basic guide to demonstrate implementation of some of the above advice - race day fuelling will always be unique to the event and individual, particularly in winter.

Before

• 3–4 hours prior: Carb-rich meal (2–4g/kg) + some protein – keep low in fat and fibre to reduce GI issues (Naderi et al., 2023).

• 30–60 minutes prior: Easily digestible carb snack (30–60 g). Warm porridge, banana, or a warm sports drink works well in cold weather.

During

• Carbs: 30–90 g/hour. For events >2.5 hours, use multiple transportable carbs (glucose + fructose) for up to 90 g/h (Cao et al., 2025).

• Trial mixing in more real foods/options with fats and proteins: mini sausage rolls, pork pies or scotch eggs, pepperami, packs of noodles, chilli or porridge for longer races with checkpoint stops. Think easily digested comfort food.

• Fluids: Sip warm electrolyte drink every 15–20 minutes.

• Logistics: Keep gels/bars inside clothing to prevent freezing; pre-open wrappers for gloved hands.

• Mood can dip more easily in the cold: carry extra snacks as a ‘pick me up’, don’t risk getting ‘low’ – fuel proactively.

After

• Carb to protein ratio: 3:1 within 30 minutes to replenish glycogen and aid muscle recovery (Naderi et al., 2023).

• Warm recovery meals: Soups with rice/pasta + protein are ideal for rehydration, refuelling, and rewarming.

Summary

• Winter endurance events increase reliance on carbohydrates and elevate energy needs.

• Hydration is easily overlooked in the cold — build drinking into your plan.

• Warm, easy-to-digest, carb-rich foods and drinks are the most practical fuelling options.

• Recovery nutrition is critical to replenish glycogen, support immune function, and restore core temperature.

Fuelling strategies for winter endurance events should balance science with practicality. Planning ahead is imperative, and developing a race day nutrition strategy should be viewed as part of the multifactorial approach to challenging winter events.

References:

Cao, Y., Gao, H., Zhang, L. and Jeukendrup, A., 2025. Carbohydrate and fluid requirements for endurance exercise: New insights and practical applications. Sports Medicine, 55(2), pp.123–136.

Castellani, J.W. and Tipton, M.J., 2015. Cold stress effects on exposure tolerance and exercise performance. Comprehensive Physiology, 6(1), pp.443–469.

Castellani, J.W., Young, A.J., Sawka, M.N. and Pandolf, K.B., 2016. Human physiological responses to cold exposure: Carbohydrate metabolism, fluid balance, and gastrointestinal function. Experimental Physiology, 101(1), pp.39–47.

Jeukendrup, A.E., 2011. Nutrition for endurance sports: Marathon, triathlon, and road cycling. Journal of Sports Sciences, 29(sup1), pp.S91–S99.

Jeukendrup, A.E., 2014. A step towards personalized sports nutrition: Carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), pp.S25–S33.

Kenefick, R.W., Ely, B.R., Cheuvront, S.N. and Sawka, M.N., 2004. Dehydration and symptoms of illness in cold weather. Medicine & Science in Sports & Exercise, 36(2), pp.317–325.

Naderi, A., Earnest, C.P., Lowery, R.P., Wilson, J.M., Willems, M.E.T. and Kreider, R.B., 2023. Nutritional strategies for endurance athletes: Recent advances and future directions. Nutrients, 15(3), p.563.

Public Health England, 2016. Vitamin D and Health. Scientific Advisory Committee on Nutrition (SACN). London: Public Health England. Available at: https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report [Accessed 15 September 2025].

Straat, M.E., Hansen, J.E., Rasmussen, P. and Nybo, L., 2022. Metabolic demands in cold-exposed endurance athletes. European Journal of Applied Physiology, 122(4), pp.889–900.

USU Extension, 2023. Carbohydrate needs for athletes. Utah State University Extension. Available at: https://extension.usu.edu/nutrition/ [Accessed 15 September 2025].