2012-05-21

Mathematics is one of the latest weapons to be wielded in the war against obesity. A new mathematical model for weight loss has been created that dispels many myths about shedding pounds. The math also reveals obvious reasons for America’s obesity epidemic that can be understood without a complex equation.



Numbers don’t lie

In mathematics, when an equation has a solution, the outcome is indisputable. Unlike language, the facts revealed by math cannot be spinned, dodged or sugar coated. Scientists at the National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK) are using numbers to figure out why the U.S. obesity rate has spiked from about 20 percent to over 30 percent since the 1970s.

Mathematical physiologist Kevin Hall was hired by the NIDDK to develop a model for predicting how a person’s body composition changes in response to what they eat. The math shows that conventional wisdom about diet and exercise to lose weight is vastly oversimplified, if not completely wrong.

Mathematical mythbusters

For decades, doctors and nutritionists have followed the rule of thumb that to lose one pound, a person had to account for 3,500 calories by eating less and exercising more. By crunching the numbers, Hall found that the body’s metabolism slows as weight is lost. This could explain the “yo-yo” effect that dieters experience when their lost pounds are found again.

Hall’s model also shows that the fatter a person gains weight much more easily than a thinner one. It also provides mathematical proof that successful, permanent weight loss takes time because the body needs a chance to reach equilibrium. The model predicts that if a dieter eats 100 fewer calories a day, he or she will weigh 10 pounds less after three years and stay there—unless 100 daily calories are added back.

Applied mathematics online

Working with Carson Chow, a senior investigator at the National Institutes of Health, Hall has used his model to develop an online weight simulation tool that predicts the outcome when people of varying weights, diets and exercise habits try to lose weight. Currently the online tool is rather raw and not very user-friendly. But physicians and nutritionists will find it a useful tool to help people get healthier.

Cheap food and obesity

Chow applied mathematics to pinpoint the root cause of the obesity epidemic. The answer was obvious: overproduction of food in the U.S. It may have started in the 1970s when the government went from paying farmers to hold back on production to encouraging them to maximize production. Farms became more productive and the price of food fell. Cheaper food added about 1,000 calories a day to the American diet.

Dispelling another obesity myth with mathematics, Chow found that while the obesity rate has skyrocketed over the last 30 years, levels of physical activity haven’t changed. As for the argument that people who become obese do so because of genetics, if they lived in a society without a glut of cheap food, they wouldn’t get obese. According to Chow, “If food were expensive, you couldn’t have fast food.”

Things could be worse

Math has also shown that as fat as the country has become, the obesity epidemic could be a lot worse. Because of an endless supply of cheap food, Americans are wasting food at a progressively increasing rate. If that food were eaten, people would be even heavier. Plus, statistics showing that the U.S. obesity rate has peaked must be taken with a grain of salt, because the long recession has made food more expensive.

When the economy recovers, all bets are off.

Sources: New York Times, Inside Science, American Association for the Advancement of Science, National Institutes of Health

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