The Fattening of Americans

Recent data suggests that overweight and obese Americans appear to be aging faster than those who remain in the normal weight range (shorter telomeres). Not surprisingly, overweight and particularly obese Americans have a significantly shorter life expectancy than normal weight Americans.

Studies of human population groups following a hunter-gatherer lifestyle have observed that overweight and obesity are very uncommon. In addition, people living in hunter-gatherer cultures, presumably similar in many ways to that of ancient human ancestors, tend to hit their peak body weight when they are in their early to mid-20s. By contrast, in modern America, body weight tends to increase in the majority of Americans at least into their 50s and 60s, and sometimes even into their 70s. Today, about 65% of American adults are above normal weight. This cross-cultural data does not mean 35% of Americans will never have a weight problem.

An important question for which we have little data is what is the risk of normal weight American adults becoming overweight or obese? The fate of the minority of middle-aged, yet still normal weight, Americans is unclear. Are they somehow immune to the fattening of Americans? Or, are most of them destined to become overweight or obese in the future?

Study Follows Normal Weight Americans

Researchers examined data from the Framingham Heart Study to determine the future risk of 4,117 normal weight people in their 30s, 40s and 50s, becoming overweight or obese over 30 years of follow-up.

? For both men and women who were normal weight in their 30s and 40s, the calculated risk of becoming overweight or obese over the next 30 years was more than 60%.

? For that shrinking minority of men and women who made it into their 50s having remained normal weight, still 55.5% of the women and 48% of the men became overweight or obese over the next 30 years.

? About one-third of women who were not overweight in their 30s, 40s and 50s became obese. For men, the risk of obesity was similar, except for those in their 50s who had a slightly lower risk of becoming obese (25.9%).

? Overall, the researchers found more than 90% of men and more than 80% of women became overweight or obese during their lifetime.1

This study examined only those of European ancestry. It is known that Native Americans, along with African and Hispanic Americans, are even more prone to become overweight and obese than White Americans. Some of the data was collected back in the 1970s and 1980s when Americans were less likely to become overweight or obese.

Weight Gain in Adulthood Unnatural

Among those human cultures where modern foods and energy-saving devices are largely unavailable (like rural China) or shunned (like the Amish in Pennsylvania) less than 5% of adults are overweight and less than 1% are obese. Average body weight is steady or declines slightly with age. It is increasingly clear that modern foods are fattening because they are high in fat and/or refined carbohydrates, calorie-dense and low in fiber. Certainly inactivity, aided and abetted by TVs, computers and numerous energy-saving devices in the home and at work have diminished our need for calories, while modern foods promote increased calorie intake. Unless Americans are willing to exercise regularly and eat more low-fat, high-fiber foods, it is likely that most Americans will become overweight or obese.

By James J. Kenney, PhD, RD, FACN

Reference: 1. Ann Intern Med 2005;143:473-80