NYTimes | FOR
most of the last century, our understanding of the cause of obesity has
been based on immutable physical law. Specifically, it’s the first law
of thermodynamics, which dictates that energy can neither be created nor
destroyed. When it comes to body weight, this means that calorie intake
minus calorie expenditure equals calories stored. Surrounded by
tempting foods, we overeat, consuming more calories than we can burn
off, and the excess is deposited as fat. The simple solution is to exert
willpower and eat less.
The
problem is that this advice doesn’t work, at least not for most people
over the long term. In other words, your New Year’s resolution to lose
weight probably won’t last through the spring, let alone affect how you
look in a swimsuit in July. More of us than ever are obese, despite an
incessant focus on calorie balance by the government, nutrition
organizations and the food industry.
But
what if we’ve confused cause and effect? What if it’s not overeating
that causes us to get fat, but the process of getting fatter that causes
us to overeat?
The
more calories we lock away in fat tissue, the fewer there are
circulating in the bloodstream to satisfy the body’s requirements. If we
look at it this way, it’s a distribution problem: We have an abundance
of calories, but they’re in the wrong place. As a result, the body needs
to increase its intake. We get hungrier because we’re getting fatter.
It’s
like edema, a common medical condition in which fluid leaks from blood
vessels into surrounding tissues. No matter how much water they drink,
people with edema may experience unquenchable thirst because the fluid
doesn’t stay in the blood, where it’s needed. Similarly, when fat cells
suck up too much fuel, calories from food promote the growth of fat
tissue instead of serving the energy needs of the body, provoking
overeating in all but the most disciplined individuals.
We discuss this hypothesis in an article
just published in JAMA, The Journal of the American Medical
Association. According to this alternative view, factors in the
environment have triggered fat cells in our bodies to take in and store
excessive amounts of glucose and other calorie-rich compounds. Since
fewer calories are available to fuel metabolism, the brain tells the
body to increase calorie intake (we feel hungry) and save energy (our
metabolism slows down). Eating more solves this problem temporarily but
also accelerates weight gain. Cutting calories reverses the weight gain
for a short while, making us think we have control over our body weight,
but predictably increases hunger and slows metabolism even more.
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