The average American weighs more than ever before because he sits more and eats more. Technological advances at work account for decreased occupational energy expenditure, but not for the rise in leisure-time TV and other physically passive pursuits. And since the average American was already overnourished in the early 1980s, hunger can't explain why we eat more than ever before.
What's driving the changes? It seems likely that broad social influences explain the trends. Although doctors, nutritionists, exercise physiologists, and expert panels advocate strongly for prudent eating and regular exercise, the food and entertainment industries push back with seductive ads that trump somber warnings. And as people get fatter, they slowly accept corpulence as the new normal and then spread their apparent embrace of extra pounds to friends and neighbors through social networks.
Nationwide progress will require broad social realignments that are dauntingly difficult and maddeningly slow. So while we must continue trying to turn the battleship of American obesity, we must also take individual responsibility for exercise, diet, and health.
What you can do
A 2011 Harvard study gives us an opportunity to see how individual choices affect a person's weight over the years. The volunteers included three populations of U.S. men and women; two groups were studied from 1986 to 2006, the third from 1991 to 2003. All of the 120,877 subjects were free of chronic diseases and were not obese at the start of the observation period.
Although all the volunteers were health care professionals, they were not immune to the American norm of slow, steady weight gain during midlife. The average gain was 0.8 pounds a year. But a closer look reveals the lifestyle factors behind the bulge:
Diet: Weight gain was linked to a high intake of potato chips, potatoes, sugar-sweetened beverages, red meat, and processed meat. In contrast, a high intake of vegetables, whole grains, fruits, nuts, and yogurt appeared to protect against gaining weight. In all, people with the least desirable dietary patterns gained 1.4 pounds a year more than their peers who ate the most healthfully.
Exercise: Physical activity protected against weight gain. In this case, the greatest benefits went to people who began to exercise or increased their activity level during the study period.
Television: TV is the enemy of exercise and the friend of snacking. It's no surprise, then, that the people who watched the most TV gained the most weight. Over each four-year period, each daily hour of TV added 0.8 pounds.
Sleep: It's Goldilocks redux. Sleeping too little (less than six hours a day) or too much (over eight hours a day) predicted the greatest weight gain — but people who slept just the right amount experienced the least weight gain.
Alcohol:Eating right, exercising more, sitting less, and sleeping well are all wise lifestyle choices. Alcohol can go either way; moderate drinking (up to two drinks a day for men) appears to reduce the risk of heart attack and stroke, while heavy drinking is bad news for health. But alcohol is a calorie-dense food, packing more calories (7 per gram) than protein or carbs (4 per gram) and almost as much fat (9 per gram). Modest drinking may be a wise choice for some men, but one drink a day provides enough calories to pack on 10 pounds over the course of a year.
Smoking: For anyone who smokes, quitting is the first step to better health. People who kicked the habit during the study gained an average of 5.2 pounds during the next four years. Still, quitting is the right thing to do, and a combination of diet and exercise can attenuate the weight gain.
The Harvard study shows that individual lifestyle choices go a long way toward explaining weight gain and obesity. You can make whatever choices work best for you, but for weight control and good health, a prudent overall lifestyle pattern will produce the best results.
Do the math
Obesity is complex, and weight control is controversial. Are people fat because of their genes, hormones, metabolism, or habits? Will you shed pounds with a low-carb, high-protein, high-fat diet, or with a low-fat, moderate-protein, high-carb diet? Is high-intensity aerobic exercise better than moderate exercise, or is strength training the best of all?
Medical research is littered with conflicting answers, and the controversies are sure to continue. If these questions appear difficult, even unanswerable, it's because they are the wrong questions. In the final analysis, weight gain is a matter of simple but unforgiving arithmetic: if you take in more calories than you burn, you'll gain weight — but if you burn more than you take in, you'll reduce.
To control your weight, take in fewer calories. It's a real challenge in 21st-century America, but you'll find it easier if you choose fruits, vegetables, whole grains, low-fat or nonfat dairy products, and fish instead of sugary drinks, red meat, processed foods, and whole-fat dairy products.
To control your weight, exercise more. Thirty minutes of brisk walking nearly every day is a fine start, but for weighty problems, double the amount of moderate exercise or add intense exercise and weight training as your health permits.
To control your weight, buck the national trend by making wise lifestyle choices. After all is said and done, the choice is yours.
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