This is Part 1 of a five-part series. Part 2 will discuss whether these statistics about the “obesity epidemic” are believable — a specific example of how we decide what’s true and what’s not. Part 3 talks about the health consequences of overweight and obesity. Part 4: the causes of the obesity problem. Part 5: what can be done about the obesity problem — and how this relates to politics.
You can hardly pick up a magazine or newspaper these days and not read something about being fat and losing weight. Headlines trumpet that we’re in the midst of an obesity “epidemic” — not only in the rich countries but even in poorer countries around the world. But is this epidemic real?
Then there’s the debate about the health effects of being “overweight” — not really fat (that is, “obese”), but just a few pounds above what’s considered normal. Some scientists argue that being even a little overweight increases the risk of dying early or getting heart disease, diabetes, or cancer. Other researchers claim that being a little heavy isn’t bad for you and, in fact, may even be good for you if you’re middle-aged or older.
Finally, there’s tremendous controversy about the causes of obesity as well as the best way to lose weight and keep the pounds off. Do you have to eat less or just change what you eat? What about low fat and low carbs. Soda and fruit juice? Where does exercise fit in?
All of which brings up a basic question for all of us: when it comes to important — and maybe even controversial — questions, how do we know what’s really true? That’s a question that matters not only for health, but for everything we do in our personal lives, our work, and our political activities.
Let’s look at some facts — in this case, statistics collected by the U.S. National Center for Health Statistics (You can get information on this issue from the website http://www.cdc.gov/nccdphp/dnpa/obesity).
How Do You Define ‘Fat’?
“Overweight” and “obese” are both terms for ranges of weight that are greater than what is generally considered healthy for a given height. For adults, overweight and obesity ranges are determined by using weight and height to calculate a number called the “body mass index” (BMI). BMI is used because, for most people, it goes along with their amount of body fat. BMI is calculated by dividing a person’s weight in kilograms by height in meters squared:
BMI = weight (kg)/height (m2)
To figure out BMI using pounds and inches, multiply weight in pounds by 700, divide the result by height in inches, and then divide that result by height in inches a second time. You can find a BMI calculator at http://www.nhlbisupport.com/bmi).
BMI is used to classify people as “overweight” or “obese” as follows:
* An adult with a BMI between 25 and 29.9 is considered overweight.
* An adult with a BMI of 30 or higher is considered obese.
How Fat Are People in the United States?
What do the statistics based on BMI show? In the U.S., the amount of overweight and obesity in the population has increased sharply since the 1970’s for both adults and children. Two national surveys (NHANES — the National Health and Nutrition Examination Surveys) show that among adults aged 20-74 years, the amount of obesity increased from 15.0% (in the 1976-1980 survey) to 33% (in the 2003-2004 survey). These two surveys also show increases in overweight among children and teens. For children aged 2-5 years, the amount of overweight increased 5% to 14%; for those aged 6-11 years, from 6.5% to 19%; and for those aged 12-19 years, from 5% to 17%. See included graphs for another view of the trends in overweight and obesity in the U.S.
How Fat Are People Around the World?
This is indeed a world-wide problem, reflecting capitalist development trends in many countries (more high-calorie food available and more sedentary lifestyles as people move from agricultural work to office and factory jobs). (Data here from World Cancer Research Fund: Diet, Nutrition, Physical Activity, and Cancer, 2007.) Most recent estimates suggest that in 2002 there were 1 billion overweight or obese people worldwide. In China, where capitalism has returned with a vengeance, the amount of underweight adults has decreased and the numbers of people who are either overweight or obese has risen substantially. In 2002 there were 184 million overweight and 31 million obese people in China, out of a population of 1.3 billion.
The World Health Organization has found that over a 10-year period in the 1980s and ‘90s, the average BMI increased in most populations. Historically, starvation, underweight, and infection were the main nutrition-related public health problems in middle- and low-income countries. This is no longer the case. Surveys have shown that overweight exceeds underweight in most model- and low-income countries, including those in North Africa and the Middle East, Central Asia, China, and Latin America. The rise of overweight and obesity since the mid-1970s has been two to four times faster in lower-income than higher-income countries. In some poorer countries, scientists now speak of a “dual burden”: obesity alongside starvation.J