Why Does Swimming Make You So Hungry?

February 25, 2025 | 5 min read

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Guest blog by Scott Tindal, Co-founder of Fuelin

Key Takeaways:

• Swimming makes you feel hungrier due to the higher energy demands of moving through water, which is denser than air, requiring more significant muscular effort.
• The body struggles to regulate temperature in water, leading to increased metabolic activity and caloric burn, particularly in colder pools or open water.
• Research shows that swimming burns a significant amount of energy across all levels of athletes, from professionals to amateurs, influencing post-exercise appetite.
• Hydration is essential in managing hunger cues and preventing misinterpretation of thirst as hunger.

Why Swimming Increases Hunger

You're not alone if you’ve ever finished a swim session ravenous. Many swimmers—whether elite professionals or casual pool-goers—experience an intense surge in hunger after training. But why does swimming, more than other forms of exercise, leave you craving food?

Science provides compelling explanations for energy expenditure, thermoregulation, and hydration status. Unlike running or cycling, where your body moves through the air, swimming forces your muscles to push through the water, which is almost 800 times denser than air. This difference in density leads to increased resistance, requiring more muscular effort and energy to sustain movement, particularly in freestyle, butterfly, and breaststroke.

Additionally, water is a thermal conductor, meaning heat is lost faster from the body than in air. In colder pools or open water, this increases metabolic activity to maintain core temperature, potentially increasing post-exercise hunger cues.

Energy Expenditure in Swimming: The Numbers

To quantify the energy demands of swimming, let’s examine caloric burn across different levels of athletes.

• Professional Swimmers (e.g., Olympic-level 1500m freestyle swimmers) can burn 800–1,500 kcal per hour in intense training sessions (Rodriguez et al., 2009).
• Elite Swimmers burn slightly less due to lower muscle mass and metabolic rate but still expend 600–900 kcal per hour in heavy training loads.
• Age Group and Amateur Swimmers typically burn 400–700 kcal per hour, depending on intensity, stroke efficiency, and water temperature.

Swimming's unique metabolic cost, compared to other endurance sports like cycling or running, contributes to heightened post-exercise hunger. Research has found that swimmers tend to consume more calories after exercise than runners or cyclists when matched for energy expenditure.

The Role of Cold Water in Hunger Regulation

A critical factor that differentiates swimming from other endurance sports is thermoregulation. When you swim, your body is immersed in water, which cools the skin and reduces core temperature faster than air. This triggers the cold-induced thermogenic response, activating brown adipose tissue (BAT) to generate heat and compensate for the cooling effect.

Interestingly, research suggests that cold water exposure blunts post-exercise appetite regulation due to hormonal responses. A study by Brown et al., 2009 found that individuals who exercised in water at 20°C (68°F) consumed 44% more calories post-exercise than those who exercised in water at 32°C (90°F).

This means training in colder water increases caloric burn and concurrently amplifies hunger by reducing the appetite-regulating response. This is likely due to disruptions in the signalling of leptin and ghrelin, two key hormones that regulate appetite.

Why Swimming Hunger Feels Different From Other Sports

Many endurance athletes report that hunger after swimming feels more intense and immediate than cycling or running. This is due to a combination of factors:

• Blood Flow Redistribution: Swimming does not engage the gut in the same gravitational way as running or cycling, leading to slower digestion & reduced gastric emptying during the activity. Once the session ends, digestion resumes, and hunger kicks in.
• Hormonal Response: Research indicates that ghrelin (the hunger hormone) spikes higher post-swim than land-based endurance exercise
• Lower Core Temperature Post-Swim: The body seeks energy to restore warmth, leading to an instinctive drive to eat more food.

Hydration and Hunger: The Missing Link

One commonly overlooked aspect of post-swim hunger is dehydration. Because you don’t feel sweat evaporating in water, you may not notice fluid loss, leading to underhydration during training. Several studies have found mild dehydration (1–2% body weight loss) can increase hunger perception, leading swimmers (& other athletes) to mistake thirst for hunger post-workout.

• Pre-Swim: Drink 500ml of water or an electrolyte solution 30–60 minutes before swimming.
• During Swim: Aim for 150–250 ml every 15–20 minutes, especially in long sessions that exceed 60 minutes.
• Post-swim: Rehydrate with 1.5-2.0 times the amount of fluid lost in body weight to prevent excessive hunger due to dehydration.
• Use Fuelin: Utilise the FUEL/HYDRATION TEST feature to monitor sweat rate for sims (bike/run/gym).

Final Thoughts: Managing Post-Swim Hunger Smartly

Swimming’s unique physiological demands—high energy expenditure, cold water exposure, and hydration challenges—contribute to intense post-exercise hunger. While this hunger is natural, athletes should focus on nutrient-dense foods that support recovery rather than simply indulging in high-calorie, low-nutrient meals.

To optimize swim nutrition:

✅ Follow your Fuelin Nutrition Plan
✅ Eat a snack before every swim session (read our swim nutrition blog post here)
✅ Prioritize protein & healthy fats to enhance satiety after your swim.
✅ Include complex carbohydrates to replenish glycogen stores after your swim.
✅ Stay ahead of hydration needs to prevent mistaking thirst for hunger.

Understanding the science behind swimming-induced hunger can help you fuel smarter and perform better without overcompensating for energy burned in the water. At Fuelin, we use a science-backed fueling approach to ensure athletes consume the correct fuel at the proper time for the correct reasons. By following our structured fueling guidelines and using our Red, Yellow, and Green snack recommendations, athletes can train smarter, recover faster, and perform better.

References:

1. Holmér, I. “Energy cost of arm stroke, leg kick, and the whole stroke in competitive swimming styles.” European Journal of Applied Physiology and occupational physiology vol. 33,2 (1974): 105-18. doi:10.1007/BF00449512

2. Ron Maughan and Louise Burke (2012) Nutrition for athletes: a practical guide to eating for health and performance: based on an International Consensus Conference held at the IOC in Lausanne in October 2010 / prep. by the Nutrition Working Group of the International Olympic Committee.

3. Péronnet, F, and D Massicotte. “Table of nonprotein respiratory quotient: an update.” Canadian journal of sport sciences. Journal canadien des sciences du sport vol. 16,1 (1991): 23-9.

4. Kenny, G P et al. “The effect of ambient temperature and exercise intensity on post-exercise thermal homeostasis.” European Journal of Applied Physiology and Occupational Physiology vol. 76,2 (1997): 109-15. doi:10.1007/s004210050221

5. Celi, Francesco S. “Brown adipose tissue--when it pays to be inefficient.” The New England Journal of Medicine vol. 360,15 (2009): 1553-6. doi:10.1056/NEJMe0900466

6. Broom, David R et al. “Influence of resistance and aerobic exercise on hunger, circulating levels of acylated ghrelin, and peptide YY in healthy males.” American journal of physiology. Regulatory, integrative and comparative physiology vol. 296,1 (2009): R29-35. doi:10.1152/ajpregu.90706.2008

7. Carroll, Harriet A. et al. “Hydration status affects thirst and salt preference but not energy intake or postprandial ghrelin in healthy adults: A randomized crossover trial.” Physiology & behavior vol. 212 (2019): 112725. doi:10.1016/j.physbeh.2019.112725