Nutrition Science and Everyday Application - beta v 0.1

408 ALICE CALLAHAN, PHD, HEATHER LEONARD, MED, RDN, AND TAMBERLY POWELL, MS, RDN
Despite the gravity of the problem, no country has yet been able to implement policies
that have reversed the trend and brought about a decrease in obesity. This represents
“one of the biggest population health failures of our time,” wrote an international group
of researchers in the journal The Lancet in 2019. 6 The World Health Organization has set
a target of stopping the rise of obesity by 2025. Doing so requires understanding what is
causing the obesity epidemic; it is only when these causes are addressed that change can
start to occur.
CAUSES OF THE OBESITY EPIDEMIC
If obesity was an infectious disease sweeping the globe, affecting billions of people’s health,
longevity, and productivity, we surely would have addressed it by now. Researchers and
pharmaceutical companies would have worked furiously to develop vaccines and medicines
to prevent and cure this disease. But the causes of obesity are much more complex than
a single bacteria or virus, and solving this problem means recognizing and addressing a
multitude of factors that lead to weight gain in a population.
Behavior
At its core, rising obesity is caused by a chronic shift towards positive energy
balance—consuming more energy or calories than one expends each day, leading to an
often gradual but persistent increase in body weight. People often assume that this is an
individual problem, that those who weigh more simply need to change their behavior to eat
less and exercise more, and if this doesn’t work, it must be because of a personal failing, such
as a lack of self-control or motivation. While behavior patterns such as diet and exercise can
certainly impact a person’s risk of developing obesity (as we’ll cover later in this chapter), the
environments where we live also have a big impact on our behavior and can make it much
harder to maintain energy balance.
Environment
Many of us live in what researchers and public health experts call “obesogenic environments.”
That is, the ways in which our neighborhoods are built and our lives are structured influence
our physical activity and food intake to encourage weight gain . 7 Human physiology and
metabolism evolved in a world where obtaining enough food for survival required significant
energy investment in hunting or gathering—very different from today’s world where more
people earn their living in sedentary occupations. From household chores, to workplace
productivity, to daily transportation, getting things done requires fewer calories than it did in
past generations.