When the fuel levels in your blood drop, your body reacts and triggers a response by making you hungry to refill the fuel. Exercise can either make you hungry or decrease your hunger, which depends on the intensity of the workout. Low intensity workouts triggers a hunger response in the body. Low intensity swimming will therefore make you hungry. On the other hand, higher intensity workouts usually reduce your hunger. During high intensity workouts signals are released that indicate the body is full of fuel, which in return makes you less hungry.
Overall, higher intensity workouts seem to reduce hunger, but in the pool however this is not the case. The cold temperature of water triggers a contratrictive signal, which overrides the signal of hunger suppression, and thus makes you hungry.
This is in contrast to sports like football or jogging, which mainly take place outdoors, away from the temptations of easily accessible calories. This explanation is logical, but also easily debunked as the main reason for the increased appetite of swimmers. Studies looking into the effects of different sports on weight loss provide evidence against the possibility of the availability of vending machines, as researchers present participants with the same buffet options after exercise.
Increased appetite after swimming has led to a number of studies concluding that swimming is a less effective weight loss intervention than walking or cycling of a similar intensity — regardless of the availability of food [1]. The front crawl for example recruits muscles from the chest and lats, whereas the butterfly will target the shoulders, chest, and back. In one training session a swimmer will typically engage a significantly greater proportion of their muscles than athletes from other sports, such as cycling.
The energy expenditure spread over a number of muscle groups is one potential explanation for increased appetite. Interestingly, and in contrary to the above theory, when researchers measured energy expenditure in relation to body mass across a number of sports, swimming ranked among the lowest — despite using more muscle groups.
It therefore appears that although swimming might utilise more muscle groups, this does not correlate with total energy expenditure. An interesting theory behind the increased appetite after swimming is that a session will typically last longer than in other sports. A swimmer may spend three to four hours in and around the pool, whereas those cycling, running, or playing football, will rarely be exercising for more than two hours.
This effect can be explained by hormonal changes suppressing appetite during exercise. This appetite suppression is an important evolutionary trait, as it means that we can sustain exercise for a prolonged period without needing to break for food.
The exact mechanism behind this finding, and even the hormones involved, is still not fully understood. While a concise theory, the difference in total exercise time can be easily debunked using the same method as the availability of food — directly comparing athletes undertaking different sports, while controlling the variables. In this case, the amount of time spent exercising can be controlled, and interestingly swimmers are still noted to have an increased appetite compared to other athletes, and so there must be a more significant factor.
There is some logic to the theory, but swimmers are exercising — which means generating heat — can cold water really have that much effect? As it turns out, cold water is the most significant factor in post-exercise increased appetite, to a much greater degree than cold air.
The results of this study were mirrored by another looking at cyclists submerged in varying temperatures of water, compared to those on land [5]. Interestingly, cyclists submerged in warm water ate the least calories — even less than those on land — suggesting that temperature plays a larger role in post-exercise appetite than previously thought.
Of course, the effect that swimming has on your appetite has nothing to do with its effectiveness as a form of exercise—and on that front, it's one of the best there is, especially for people in search of a low-impact way to stay fit. But if you're watching your diet and don't want to overindulge, you can take the edge off the post-swim munchies by taking a quick, brisk walk to raise your body temperature before you chow down.
BY Kat Rosenfield. Big Questions exercise swimming pool Live Smarter. Subscribe to our Newsletter! When we accounted for the energy used during swimming and cycling, the participants were still in an energy deficit in both exercise trials compared to the control trial, but the deficit was greater after cycling. When we looked to see if there were any differences between men and women their responses were the same.
This is important because it is sometimes suggested that for women, exercise is not as effective for weight management because women often expend less energy during exercise.
But this suggestion is not always supported by the evidence as highlighted by a recent review , which concluded that men and women typically have similar appetite and food intake responses to exercise. The reason for this appetite-stimulating effect of swimming is not understood. One possible reason relates to the suggested link between temperature specifically body heat loss and food intake. In colder temperatures, food intake may increase as a mechanism to generate body heat through diet-related thermogenesis.
Despite the fact that swimming would have generated body heat during our experiment, immersion in the cool water would likely have led to overall body heat loss.
Further research studies in swimming are needed to confirm this. This is plausible because there are specific regions of the brain linked to appetite and reward, and non-homeostatic factors such as eating for pleasure or the motivation to eat certain foods over others can also influence appetite and eating behaviour.
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