Does Swimming Make Me Fat?

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.

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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


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