TCS Daily


Unhealthy Lifestyle

By Ruth Kava - April 16, 2003 12:00 AM

Anyone who reads health news or watches it on TV must surely be aware of the recent spate of reports on the increasing adiposity of the American public-by some estimates well over half of adults are overweight or frankly obese. Between 1980 and 1999, the prevalence of obesity among adults aged 20-74 years has increased from 15 to 27 percent. Similarly, the number of charges and counter-charges bouncing around the airwaves and Internet has increased exponentially, and are almost too numerous to keep track of. A plethora of products are hailed as "miracle cures" that allow one to lose weight while sleeping (no decrease in calories or increase in activity required), and a variety of foods or ingredients-sodas, red meat, high-fructose corn syrup, French fries, sugar, white bread-are labeled as the major culprits. The implication of many of these charges seems to be that if Americans just stopped eating the bete noire du jour, we would return to our former lithe and slender selves. I don't think so-the problem is both simpler and more complicated than that-it's calorie imbalance on a grand scale and there is no really easy fix.

Obesity is defined as an excess of body fat (not just body weight). There are some accurate ways to actually determine the amount of fat on a person's body, but most are pretty technical or require expensive equipment. The most widely used index to estimate whether one is too fat or not is the Body Mass Index (BMI), which is basically a ratio of weight to height. Based on the increased incidence of death and disease (e.g., heart disease, diabetes) with increasing excess of body fat, a BMI of 25-29.9 is considered overweight, while a BMI of 30 or more is considered obese. An important caveat is that the BMI does not take body composition into account. This means that a serious athlete or body-builder, who has more than the typical proportion of muscle, might have a relatively high BMI, but not be overly fat. The BMI index is most accurate for sedentary individuals, which unfortunately, seems to mean the majority of Americans.

Not only is the amount of body fat an important clue to health risk, but the distribution of the excess on the body is also key. A concentration of excess fat in the abdominal area is of greater concern than excess distributed lower down on the thighs. This central or upper body obesity is typical of men and some women (the "beer belly" or "apple" profile); most women, when they add fat tend to put it on their lower hips and thighs ("saddle bags" or "pear profile"). Obese people with an apple distribution of body fat have a greater tendency to disordered metabolism, with characteristics such as insulin resistance and higher than normal levels of blood lipids.

So is it nature or nurture-genetics or environment-that is responsible for our national epidemic of obesity? Actually, elements of both are important. Certainly some people are genetically more prone than others to gain fat. Studies of identical twins have shown that when eating excess calories, twins respond more similarly to each other than to other, unrelated, sets of twins. And at some time in our evolutionary past, the propensity to efficiently store calories as fat was probably very much to one's advantage. But this was in a time when people didn't have regular access to three meals plus snacks every day. The ability to pack away calories during feast time likely meant a better chance to survive the lean times. But this can't explain the great increases in obesity in the United States over just the last 20-30 years: evolutionary change occurs over millennia, not decades.

The other possible contributor to the increased prevalence of obesity is, of course, the environment, which has certainly changed in the latter half of the 20th century. At no other time in our history has food been as cheap or ubiquitous as it has become since the 1950's. Further, we now have products available that weren't even thought of by consumers back then. Take a staple like milk, for example-in 1950 one could buy whole or skim milk, cream in fresh form at the store. For longer storage, there was sweetened, condensed milk or evaporated milk in cans. In 2003, we can buy whole milk, reduced fat (2%), low fat (1%), non-fat (skim) milk: we can get these forms with or without the milk sugar lactose, in some cases with or without extra calcium or protein, and in shelf-stable ultra-high temperature pasteurized forms. Of course, other foods and beverages also come in a myriad of forms: low fat, low sugar, with or without various vitamins or herbal supplements. It's very easy, faced with all this information overload to forget that the basic key to weight control is the balance between calories consumed and calories burned.

And food is everywhere-in an urban setting there are salad bars, fast food outlets, and coffee houses on nearly every block. Many schools (especially high schools) have vending machines that make food available virtually all the time.

Another change in the food environment is the increase in sizes of portions served in restaurants, private homes, and available in stores. While a typical soft drink used to come in a 6 and 1/2 ounce bottle, it is now difficult to find anything less than 12 ounces on the grocery store shelves. A typical bagel used to weigh 2 ounces; now it's hard to find one that's less than 4 or 5!

Yet another point of confusion for many is the huge variety of diet books and systems currently available. One can find a diet that eschews all fat, all sugar, all meat, or all carbohydrates on various (usually vague) metabolic grounds. All have their devoted adherents who swear to the success of their particular program. And all probably work in the short term-because all cut calories to some extent. But, on the whole, none have passed a rigorous test-do people stick with the program long-term, or do they backslide and gain their weight back?

The other side of the energy equation-physical activity-has also changed. Some of the most obvious changes have come about since the computer revolution-especially the introduction of the Internet. Instead of going to the library to get information, we can now "google" our way to almost anything we want to know about. And children now spend hours on computer games and computer-related schoolwork; hours that in many cases used to be spent outside playing active games, bike riding, or being involved in organized sports. Many do not have regular gym classes in school any more.

On the home front, we have remote control of our televisions so we don't have to move to change channel or volume. Our appliances are ever more labor-saving and lighter in weight. Even cars are easier to drive than they used to be-in the days before automatic transmissions, power steering, power brakes, and power seats, drivers had to use a few more calories to parallel park, adjust seat position, and just drive. Although these changes are each small in and of themselves, they add up over time-and so do the calories they save.

Because our lifestyles and environment have changed in so many small ways, it is difficult to suggest one "fix" for it all. Certainly, simply taxing so-called "junk foods" to decrease their consumption (as some have suggested) misses the boat. One can consume too many calories from yogurt and whole wheat pasta as well as from chips and fries. While it is true that the former will provide nutritional advantages, it's the calories that count most when dealing with body weight problems.

The real answer is not very exciting, and for many of us, not very easy-attention to lifestyle is the basis for dealing with the body weight challenge. Having many choices means having to make health-promoting ones, and requires a little knowledge about which ones are right for us individually.

Ruth Kava, Ph.D., R.D. is Director of Nutrition at the American Council on Science and Health.
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