Nutrition Science and Everyday Application - beta v 0.1

INTRODUCTION TO ENERGY BALANCE 369
burn about 10,000 calories per day on his journey, and he knew that if he didn’t pack enough
food, he wouldn’t have the strength to complete this epic test of endurance in extreme
conditions. Previous explorers died in the Antarctic because they didn’t pack enough food.
Figure 7.2. O’Brady and Rudd raced across a landscape similar to that shown in this photo
from Antarctica—a polar desert and the coldest, windiest, driest continent on earth.
But O’Brady also knew that the more food he packed, the heavier his sled would
be—ironically making him burn more calories, plus slowing him down and prolonging his
trip. So he focused on making his food calorie- and nutrient-dense but lightweight: oatmeal
with added oil and protein powder; freeze-dried dinners reconstituted with melted snow;
and 4,500-calorie slabs of a custom-made “Colin bar” made from coconut oil, nuts, seeds,
and dried fruit.
At the start of his journey, O’Brady’s sled weighed 375 pounds and contained enough food
to provide him with 8,000 calories per day. That was a bit short of the 10,000 calories he
estimated he’d burn every day, so to build up some additional energy stores, he gained
15 pounds prior to his trip. In the end, after 54 days of skiing through ice and snow, he
lost 25 pounds during his Antarctic crossing. He was successful, and while his fitness level
and determination surely played a part, the trip would have been impossible without an
adequate supply of calories.
In our daily lives, we need far fewer calories than an Antarctic explorer, and we don’t need
to schlep a two-month supply of food on our backs wherever we go. And thankfully, we get
to enjoy fresher and more interesting food options, too. But each of us, every day, whether
we’re aware of it or not, is attempting to balance the calories we consume with the calories
we burn, just like Colin O’Brady. This is the concept of energy balance—one we’ll be exploring
throughout this unit. If adults eat roughly the same number of calories as they burn each
day, their body weight will generally stay very constant. If they burn more calories than they
eat, like O’Brady was on his expedition, they’ll lose weight. If they consume more calories
than they burn, they’ll gain weight.
Energy balance may seem like a simple concept, but in practice, how many calories a