7.2: Introduction to Energy Balance

On December 26, 2018, 33-year-old Colin O’Brady of Portland, Oregon, became the first person to cross the landmass of Antarctica solo, unassisted, and without any resupply shipments. Others had crossed the continent with the help of a wind sail to propel them over the ice or with resupply drops along the way—both ways of saving precious energy—but O’Brady completed the 926-mile trek only on skis, pulling a sled packed with food, fuel, and supplies the entire way. Speed was important, because he was racing another man, Louis Rudd, a 49-year-old British Army captain. And of course, he didn’t want to run out of food hundreds of miles from the finish. Rudd finished the Antarctica crossing just two days after O’Brady.

Figure 9.1. Endurance athlete Colin O’Brady, photographed in March 2016

To prepare for the expedition, O’Brady and his team had to make careful calculations to estimate his nutrient and caloric needs. He’d be skiing all day, every day for about two months, in below zero temperatures and against constant wind. O’Brady estimated that he’d 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 9.2. 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 person eats and expends each day is influenced by so many different factors that it can be frustratingly difficult to apply. The human body has many sophisticated mechanisms that have evolved to help us protect and maintain our body weight, and in the history of our species, these mechanisms have been vital to our survival in times of food shortages. But today, we live in a world where highly palatable food is easily available and convenient, and we’re constantly bombarded with marketing messages enticing us to eat more of it. At the same time, the diet industry and media send messages saying that being thin is the same as being healthy and that restrictive dieting is the virtuous path to wellness, which ironically may cause weight gain and worsen people’s mental and physical health. Meanwhile, disparities in access to healthy food, safe places for physical activity, and healthcare have grown, all of which are associated with body weight and health. Many other factors, including the use of some medications, exposure to certain chemicals in the food supply and environment, inadequate sleep, excess stress, microbiome changes, and experiencing traumatic events, have been linked to body weight.

In this unit, we’ll explore these complex concepts and concerns and seek some answers, but we acknowledge that we raise more questions than we resolve. The truth is that researchers don’t fully understand why body weight has increased over the last several decades, much less how to change this trend. What is clear is that body weight is extraordinarily complex, and people have long been harmed by oversimplified messages to “eat less and move more” to reach a “normal” or “healthy” body weight. This approach implies that obesity is a failure of personal responsibility, but the last several decades have shown that blaming individuals for the size and shape of their bodies has not changed the trajectory of increasing body weight, and it has likely worsened people’s health by harming their relationships with food and perpetuating weight stigma.

We have done our best to approach this topic with care, recognizing that it can be very personal. We know that the language used to describe people’s bodies can be hurtful, and that encouraging people to engage in restrictive dieting practices for the purposes of making their bodies smaller can cause harm. Researchers’ understanding of body weight regulation is incomplete and still evolving, and we have tried to include different perspectives in this unit. We hope you’ll come away with an appreciation of the complexities, nuances, and uncertainties of this topic.

References

• Hutchinson, A. (2018, November 14). The Greatest Challenge on a Solo Antarctic Crossing? Food. Retrieved October 13, 2019, from Outside Online website: https://www.outsideonline.com/2365661/colin-obrady-how-fuel-solo-unassisted-antarctic-crossing
• Neville, T. (2019, August 15). Colin O’Brady Wants to Tell You a Story. Retrieved October 13, 2019, from Outside Online website: https://www.outsideonline.com/2400795/colin-obrady-profile-antarctica
• Skolnick, A. (2018, November 29). Racing Across Antarctica, One Freezing Day at a Time. The New York Times. Retrieved from https://www.nytimes.com/2018/11/29/sports/antarctica-ski-race.html

Image Credits:

• Fig 7.1. “Endurance athlete Colin O’Brady in March 2016” by Colin O’Brady is licensed under CC BY-SA 3.0
• Fig 7.2. “Christopher Michel Antarctica” by Christopher Michel is licensed under CC BY 2.0