MAYBE WE'RE TOO STRESSED
The theory: Chronic stress leads to weight gain, and chronic stress is at epidemic levels (just like obesity).
The research: Whole books have been written to explain how stress leads to weight gain -- "The Cortisol Connection: Why Stress Makes You Fat and Ruins Your Health -- and What You Can Do About It"; "Fat Around the Middle: How to Lose That Bulge for Good."
Cortisol is often called the "stress hormone" because it's part of the body's fight-or-flight response. It's a good thing when you're being chased by a lion (or chewed out by an angry boss), but many doctors and scientists believe that chronic stress is anything but good.
Studies have shown that cortisol makes people crave rich sweets in the worst way -- and pile on pounds in the worst place, around the middle, putting a body at risk for bad cholesterol, heart attacks and strokes. One study compared women with high waist-to-hip ratios to women with low waist-to-hip ratios and found that the former secreted more cortisol in stressful lab situations and self-reported more stressful feelings.
In 2007, researchers introduced a different notion of how stress is related to weight gain. Their study compared stressed mice (who had to live either in cold cages or with a bunch of mean cousins) and unstressed mice (who, relatively speaking, had the life of Stuart Little before all that bad stuff happened). When fed a high-fat, high-sugar diet, all the mice gained weight, but the stressed mice gained twice as much. The scientists found that a molecule in the stressed mice -- neuropeptide Y -- activated a gene in fat cells, causing the cells to grow in size and number. When that gene was blocked for two weeks, the mice lost 40% of the weight they had gained.
Are we more stressed these days? "I would say that modernity . . . provides more factors that are a source of stress," says Angelo Tremblay of Laval University in Quebec.
Our experts weigh in: Susan Roberts of Tufts University says lots of research shows changes in food preferences for animals under stress. And Dr. Julie Lumeng of the University of Michigan says studies have shown that obese people are less likely than others to be drug addicts or alcoholics -- "the thought being that if you use food to 'soothe your mood,' you will be less likely to need to use alcohol or drugs to 'soothe your mood.' "
