Let’s see. The fridge is stocked with butter and sour cream. The cupboard is full of sugar, salt and vanilla. What could possibly go wrong? Well, here come the holidays and once again, it’s time to talk fat.
I saw a picture taken of me a while back and was surprised to see my T-shirt bulging in front — and not with muscle. Where did that come from? I swear that belly just appeared out of nowhere! I’m often foolish, but not a fool, and know that at least according to modern physics, nothing can magically appear out of nowhere or disappear into thin air (Hollywood notwithstanding). I know that my sweet tooth not only enabled my dentist to buy a big boat, but is now doing its best to fabricate an end to my hiking career. Surely my affinity for potato chips isn’t in on the conspiracy!
My brother and I were talking about the super-lightweight backpacking gear that has become available in recent years. Eventually it occurred to us that it would be cheaper to reduce our hiking loads by reducing ourselves than by buying a bunch of new stuff. We started to wonder “Where does fat go when it’s lost?” The National Enquirer says I can “Melt Fat Away” but even so, just where would it end up if it did melt? Would I become slippery? Greasy? Fatty sweat? Do people poop more when they diet? As a proud nerd, I wanted to know, where does that fat go? The answer I found is absolutely amazing.
A short dig through one of my old textbooks turned up the following equation for when fat is “burned” by the body for energy: (I know you’re thinking “Aieeee! Not chemistry!” but the pain will be over in a jiffy. As the dentist says, you might feel just a little pinch.)
C55H104O6 + 78 O2 —> 55CO2 + 52 H2O + energy
(Fat plus oxygen turns into carbon dioxide, water and energy)
That’s one triglyceride molecule on the left, the most common body fat, plus 78 oxygen molecules we breathe in. When the energy stored in the fat is released, the atoms get rearranged into a bunch of carbon dioxide, some water and some energy. We use that energy to do things like press the TV remote, run 10 miles or keep our bodies at nearly a hundred degrees in a 65-degree room.
According to a study published in the British Medical Journal, oxidizing (burning) 5 pounds of fat requires inhaling about 6.5 pounds of oxygen (Yeah, gas has weight, isn’t that weird?) The result (puffed out breath by breath) is about 6.5 pounds of carbon dioxide and about 5 pounds of water (a little over a half-gallon). Nothing disappears. All the atoms are all still there, just reassembled by the miracle of metabolism into something different. Sort of like using the wood from an old barn to make some furniture and a couple of sheds.
Nerd Corner
Before the fat is turned into gas, the fat must first be turned into glucose and then into adenosine triphosphate molecules (quiz tomorrow) before it can be “burned”/oxidized for energy. In our bodies’ energy budget, think of fat as the bank, glucose as the ATM machine and adenosine triphosphate molecules as cash. Yes, that’s right, we exhale lost fat. Through the miracle of chemical reactions, that fat is rearranged into the form of carbon dioxide, a colorless, odorless gas and some water vapor, also a colorless, odorless gas. Believe it or not, your lost fat actually wafts away on the breeze. Jeez, don’t you just love science? This process of fat “burning” is occurring all the time of course, from the lowliest beetle to the mightiest whale. It’s the balancing of this internal commerce that keeps organisms going and the ecosystems they occupy.
Fun-to-know fat-burning extremes abound in the animal world, especially among birds. For example, by the time migrating birds start their journey, fat makes up a really high percentage of their body weight.
Fat accounts for about 15 percent of a hawk’s weight, who’ll glide most of the way south, but over 60 percent for shorebirds and a whopping 70 percent for many songbirds, who must flap the whole way. (At about 20 wing-beats a second, by the way.)
The amazing Blackpoll warbler of our East Coast will lose almost all that weight on a three-day marathon flight out over the Atlantic on their way to wintering grounds in South America. (If I were a Blackpoll warbler, I’d gain about 110 pounds between July and September and then be back to 155 in three sweaty days of heavy breathing.)
Bar-tailed godwits are about 55 percent fat before taking off on their eye-popping nonstop nine-day flight from Alaska to New Zealand. Having demonstrated a foolproof diet plan unknown to supermarket tabloids, migrants sometimes arrive at their destinations so exhausted they can’t move and are temporarily easy prey for delighted predators.
Tom Butler has a degree in zoology from the University of Washington and is a lifelong student of nature. He lives in Port Angeles and can be reached at butlert@olypen.com.
