Swimmers tend to be “fatter” than other athletes, especially ultra-distance swimmers. Swimming decreases blood pressure, but not as much as cycling or running. Swimmers rank between sedentary people and runners on blood insulin levels, but intervention studies have shown no change. Swimmers’ HDL (high-density lipoprotein – also known as “good cholesterol”) levels are very close to sedentary populations, while runners have very high HDL (Tanaka, 2010). The available research seems to suggest swimming is a lazy sport, but I think otherwise.
Swimmers and Body Fat
Why do swimmers tend to have higher adipose (fat) stores than other athletes? Yes, fat is good for floatation and insulation, but the typical age-group triathlete isn’t thinking, “Oh, I better add a thicker layer of fat to increase my swim efficiency,” right? The answer may be buried deep in your brain. One theory is that submerging your body in cold water (68F and below) triggers a hunger response. Your brain doesn’t realize this is a temporary situation, and a cascade of hormones signal tissues to store more fat for insulation, which in turn signals a need for fuel to store. The actual calories utilized during a swim session are comparable to that burnt while cycling or running at the same relative intensity, but due to the immersion in cold water, our appetite may be increased, and therefore our post-swim caloric intake could greatly exceed actual needs.
I’ve often wondered why it is that swimming, though seemingly lower in intensity than cycling and running, leaves me ravenous. No matter how long or short my swim workout, I always leave the pool feeling like I could… eat my young. Luckily, I have no young, so no toddlers have ever been sacrificed in the name of my Ironman training.
So unless you’re in need of a little extra insulation, plan your post-swim nutrition ahead of time, and stick to your plan. Unless you’re training at a moderate-to-high intensity for over 90 minutes or have another workout within 24 hours, your usual balanced meals will replenish any depleted glycogen or fat stores within your muscles before your next session. If you aren’t swimming right before a meal, bring a healthy snack to stave off post-swim hunger. Include some protein and healthy fats for increased satiety and better blood sugar regulation. If you continue to struggle with cravings, try adding a post-swim run to your workout, as running typically suppresses appetite via hormonal responses and an increase in body heat (Russell, Willis, Ravussin, & Larson-Meyer, 2009).
By Tammy Metzger