26 Jan

Of all the factors affecting obesity, perhaps the most critical is the relationship between activity levels and calorie intake. Obesity rates are rising. But how can this be happening? Aren’t more people exercising than ever before? Though the many advertisements for sports equipment and the popularity of athletes may give the impression that Americans love a good workout, the facts are not so positive. Data from a newly released National Health Interview Survey show that 4 in 10 adults in the United States say that they never engage in any exercise, sports, or physically active hobbies in their leisure time. These responses are based on answers to questions inquiring about how many respondents engaged in leisure physical activities that caused sweating or changes in their heart rate or breathing for at least 20 minutes. Women (43.2 percent) were somewhat more likely than men (36.5 percent) to be sedentary, a finding that was consistent across all age groups. Among both men and women, black and Hispanic adults had higher rates of sedentary behavior than white adults. Leisure-time physical activity was also found to be strongly associated with level of education. About 72 percent of adults who never attended high school were sedentary, declining steadily to 45 percent –≥ high school graduates and about 24 percent among adults who had a graduate-level college degree.
You probably know someone who seems to be able to eat you under the table and does not appear to exercise more than you do, yet never seems to gain weight. You may not understand how this person maintains a steady weight. With few exceptions, if you were to follow this person around for a typical day and monitor the level and intensity of activity, you would discover the answer to your question. Although the person’s schedule may not include running or strenuous exercise, it probably includes a high level of activity. Walking up a flight of stairs rather than taking the elevator, speeding up the pace while mowing the lawn, getting up to change the TV channel rather than using the remote, and doing housework vigorously all burn extra calories.
Actually, it may even go beyond that. In studies of calorie burning by individuals placed in a controlled respiratory chamber environment where calories consumed, motion, and overall activity were measured, it was found that some people are better fat burners than others. It is possible that low fat burners may not produce as many of the enzymes needed to convert fat to energy. Or they may not have as many blood vessels supplying fatty tissue, making it tougher for them to deliver fat-burning oxygen. Or perhaps in some subtle ways, these people just manage to burn more calories through extra motions. Clearly, any form of activity that helps the body burn additional calories helps maintain weight.

Women who smoke tend to weigh 6-10 pounds less than nonsmokers. After quitting, weight generally increases to the level found among nonsmokers. Weight gain after smoking cessation may be partly due to nicotine’s ability to raise metabolic rate. When smokers stop, they burn fewer calories. Another reason former smokers often gain weight is that they generally eat more after they quit, to satisfy free-floating cravings.

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