On December 26, 2018, Colin O’Brady became the first person to cross Antarctica solo, unassisted, and without resupply. During the 926-mile journey, he skied across the frozen continent while pulling a sled containing all of his food, fuel, and supplies.

Speed was also important because O’Brady was racing Louis Rudd, a British Army captain attempting the same feat. At the same time, he needed to carefully manage his food supply because running out of calories hundreds of miles from the finish could have ended the expedition. O’Brady ultimately finished two days ahead of Rudd.^[1]

More than anything else, the expedition was a challenge in energy balance—consuming enough calories to meet the enormous demands of each day. To prepare, O’Brady and his team carefully calculated his nutrient and calorie needs. He would be skiing across Antarctica every day for nearly two months, battling below-zero temperatures and relentless winds. O’Brady estimated that he would burn about 10,000 calories per day and knew that if he did not pack enough food, he would lack the energy needed to complete this extraordinary test of endurance. ^[2] O’Brady realized that previous Antarctic explorers had died from starvation.

O’Brady also realized 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 1,150-calorie bricks of a custom-made “Colin bar” made from coconut oil, nuts, seeds, and dried fruit.  He started with 280 of these bricks, enough for four each day.^[3]

At the start of his journey, O’Brady’s sled weighed 375 pounds and contained enough food to provide him with 8,000 calories each day. That was a bit short of the 10,000 calories he estimated he’d burn each day, so to build up additional energy stores, he gained 15 pounds before 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.^[4]

We need far fewer calories in our daily lives than an Antarctic explorer, and we don’t need to carry a two-month supply of food on our backs wherever we go. Thankfully, we get to enjoy fresher and more exciting food options, too. But each of us, 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 an example of the energy balance concept—one we’ll be exploring throughout this unit.

If you eat roughly the same number of calories as you burn each day, your body weight will stay constant. You will lose weight if you burn more calories than you eat, as O’Brady did on his expedition. If you overeat, you’ll pack on extra pounds.

Energy balance may seem like a simple concept, but in practice, the balance between how many calories you eat and how many you use each day is influenced by so many factors that it can be challenging to apply. Still, it’s an important concept to understand. We live in a world where food is readily available, and we’re bombarded with marketing messages telling us to eat more.  Understanding energy balance can help explain why body weight changes over time, why maintaining weight loss is often difficult, and why both excess body weight and being underweight can affect health.    In this chapter, we will explore these problems and seek some answers.

attributions

This section is an adaptation of “Introduction to Energy Balance” in Nutrition: Science and Everyday Application, v. 1.0 by Alice Callahan, PhD; Heather Leonard, MEd, RDN; and Tamberly Powell, MS, RDN, licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.