Aging and Weight Gain

It is widely assumed that aging, with it's loss of testosterone and estrogen levels in the body, brings on weight gain.
A recent study published in the New England Journal of Medicine concludes that it is food and lifestyle choices, not the natural effects of aging, that leads to the pound-a-year average weight gain in adult Americans.
The study was conducted by the Nurses' Health Study and was authored by Frank Hu, a professor of nutrition and and epidemiology at the Harvard School of Public Health. The study involved data collected from 121,000 men and women. The participants were tracked every four years for 20 years, and, on average, 17 lbs. over that 20 year period.
The article attributes most of the weight gain to unhealthy food choices like extra servings of potato chips, french fries, soda, white bread, and low-fiber cereals.
Other factors were increasingly sedentary lifestyles (hours of TV and computer use); poor sleeping habits (both too much and too little can lead to weight gain); and decreased consumption of fruits, vegetables, and other roughage. Alcohol, unsurprisingly, was another culprit.
To show that much weight gain can be prevented, the study noted that those who made the most unhealthy food choices gained nearly four pounds more in four years than those who made the healthiest dietary decisions.
The study suggests, rather than just calorie-counting, people should focus on improving their overall diet. Nuts, for example, while high in calories and fat content, actually helped provent weight gain. Exercise, of course, also helped prevent weight gain.
In my 20-plus years in the fitness field, I have heard many rational for age-related weight gain: childbirth; marriage (by men and women); "Bodily changes;" various injuries; raising young children; and the end of structured athletic careers. All may be valid to some degree. The bottom-line is, however, that maintaining a healthy diet, mixed with exercise, will prevent the weight gain that many think is inevitable.