Weight Gain in the U.S.: From Overeating or a Lack of Exercise?

American meals have been increasing in size since the 1970s, while the amount of physical activity we get has been declining. Up to now, most people assumed that the U.S.'s weight problems were due to a combination of these two trends, and that lack of exercise contributes to our obesity problems just as much as our out-of-control eating.

But now a group of Australian scientists say that American's ever-decreasing physical activity plays only a minor role in the American epidemic of overweight and obesity.

Dr. Boyd Swinburn and colleagues at Deakin University, Melbourne, presented their findings last year at the European Congress on Obesity in Amsterdam. The ever-growing amounts of food Americans eat comprise, according to Swinburn, virtually the sole cause of the alarming increase over the past 3 decades in overweight in the U.S. The researchers looked at 1,399 adults and 963 children to see how many calories they burned daily, and compared these figures to estimates of what their daily calorie needs should be to maintain a healthy weight, based on their height and weight (30 years ago and now).

The results showed that excessive caloric intake--and not too little physical activity--best explained U.S. weight-gain trends over the past 30 years. (Although the researchers emphasized the primary role of excessive caloric intake in weight gain, they stressed that they were by no means discounting the benefits of regular activity.)

The scientists now say that, to reduce this trend, American children will need to reduce their food consumption by 350 calories per day, and U.S. adults by 500 calories.

For those who do not wish to give up the extra calories, the researchers figured out that the children would need to walk an extra 150 minutes a day to achieve a healthy weight; adults would have to hike an additional 110 minutes.

Some ways to cut extra calories

• Avoid sweetened drinks (even "natural" fruit juices) or limit yourself to only 4-6 ounces per day.
• Drink more water, or at least more beverages with less than 10 calories per serving. (Exception: You may keep drinking skim and 1% milk, as well as low-sugar soymilk; almond and rice milk may be fine too, in moderation.)
• Limit foods that list any sugars among the first 5 ingredients (e.g., sucrose, dextrose, maltose, invert sugar, disaccharides, honey, glucose, molasses, monosaccharides, high-fructose corn syrup, corn syrup, etc.).
• Control your portions. Try using smaller plates and utensils and, for adults, aim for about a deck of cards' worth of meat, chicken, fish, or tofu at both lunch and dinner (smaller portions for children, depending on age, weight, etc.).

Some ways to increase physical activity

• Park the car farther away from stores when shopping; take the stairs instead of the elevator; jog to places instead of walking; on the bus, get off a few stops early; etc.
• Wear a pedometer and try to increase your total number of steps each week. Every 2,000 steps represent about a mile, and (for adults) an average of about 100 calories burned.
• Try taking a brisk 10-minute walk 3 or 4 times each day. As long as you do at least 10-minute increments and you walk fast enough to raise a sweat, you can add up all these mini-walks throughout the day and count their sum as your total minutes walked. This means that 3 brisk, short walks are the exercise equivalent of one 30-minute hike.