What Is Obesity?

Human weight and its impact on health has grown to be a topic of serious concern over the last several decades. Obesity, the condition of having an excessive amount of body fat, has become such a challenge that health professionals have attached the “E” word to it: epidemic. In fact, in June 2013 the American Medical Association (AMA) voted to declare obesity a disease, or a medical condition that requires treatment. Research suggests that most adults today are at a weight that may be a risk to their health. The World Health Organization (WHO) says worldwide obesity has nearly tripled since 1975. Some countries, including Switzerland, Italy, and Austria, have experienced a slowdown in obesity rates. However, larger increases were recorded in Mexico, Ireland, Canada, the U.K., and the United States. According to WHO, in 2022 (the most recent data available), 43 percent of adults were overweight and 16 percent were obese. In 2024, 35 million children under five years of age were overweight or obese. Trust for America’s Health, a non-profit health advocacy organization, estimated in its 2022 report on the nation’s obesity crisis that obesity costs the U.S. an increase of $170 billion each year. Obesity Canada says that more than one in three adults in Canada has obesity and may require medical support to manage their disease. These rates are rising.

If you’re in the overweight or obese classifications of the U.S. National Center for Disease Control and Prevention (CDC) or Health Canada’s Body Mass Index (BMI) chart, you are at an increased risk for developing health problems. Health officials are very concerned about weight problems among children and teens. The number of overweight children and teens in the United States and Canada has increased at an alarming rate. According to the Childhood Obesity Foundation in Canada, obesity rates in children and teens have almost tripled in the last twenty-five years. Approximately 30 percent of Canadian children and teens ages five to seventeen are currently overweight or obese. In the U.S., the CDC estimates that in the years 2017 to 2020, approximately 19.7 percent (or 14.7 million) children and teens ages two to nineteen were obese. In 2010, President Barack Obama established the Task Force on Childhood Obesity. Its goal was to return the childhood obesity rate to 5 percent by 2030. In 2022, The White House convened a national conference on dietary health for the first time in half a century, during which then-President Joe Biden unveiled a plan of his own, echoing President Obama’s. He sought to tackle the nation’s high obesity rates, which the Center for Disease Control and Prevention (CDC) believed had been increased by the COVID-19 pandemic. In November 2025, President Donald Trump announced a plan to reduce the cost of anti-obesity GLP-1 drugs like Ozempic, Wegovy, Zepbound, and Orforglipron for people enrolled in Medicare. The initiative is based on the administration’s Most Favored Nation (MFN) drug pricing policy, which ties U.S. drug prices to lower foreign ones. The drugs are available at the lower price when purchased through the federal government’s TrumpRx.gov website.

What Is a “Normal” Weight?

What is considered a “normal” weight depends on a number of factors. A muscular athlete might be 6 feet (1.8 m) tall, weigh 220 pounds (100 kg), and be considered normal or average in weight and build. A non-athlete who’s 6 feet tall and weighs 220 pounds, whose weight consists mainly of fat tissue rather than muscle tissue, is considered overweight. Weight should be considered in relation to such other factors as height, age, and rate of growth.

The first growth charts for determining appropriate weight levels came out in the 1970s. In 2000, the CDC introduced more accurate charts. These charts reflected what has become known as the Body Mass Index, or BMI. BMI charts are formulated to help you determine if you are in a weight category that could lead to health problems. However, it is important to keep in mind that it is not considered a diagnostic tool, and that you should check with your doctor to see if your BMI indicates that you might be at risk for certain health problems.

Generally, a BMI rating of 25 to 29 is considered overweight; people with a BMI score of 30 or above are considered obese. Defining obesity, though, isn’t a simple matter of calculating weight and height. For example, BMI interpretations vary slightly for those under age twenty because the body’s natural fat ratios change during normal growth. Average fat percentages also differ between young men and young women.

The BMI is a mathematical formula: your weight (in kilograms) divided by the square of your height (in meters). The measurements can easily be converted to pounds and inches. To quickly calculate your BMI in pounds and inches, use this formula:

1. Compute the square of your height (multiply your height times itself) in inches.

2. Multiply your weight in pounds by 703.

3. Divide the weight result by the height result.

Sample results: If you are 5 feet (60 inches) tall and weigh 112 pounds (50.8 kg), your BMI is approximately 22. Whether this is a low, average, or high weight depends on your age, sex, and other factors. A BMI of 23 or higher, for instance, indicates a health risk for a girl at age ten. By the time she’s sixteen, however, the same BMI suggests no problem—in fact, at that age, she could register a BMI of 28 and be considered only “borderline” in terms of overweight risk. An average BMI for a child in the first grade is approximately 16. An average BMI for a high school senior is approximately 22.

Doctors chart the BMI in relation to your age. Different charts are used for young men and young women. If your BMI ranks in the ninety-fifth percentile or above, you’re considered overweight. If it falls between the eighty-fifth and ninety-fourth percentile, you’re said to be at risk of developing an excess weight problem.

The BMI is not a perfect tool for determining a person’s body fat or health. Results may vary from child to child and teen to teen, for complex reasons. For example, the BMI does not take growth rate into account. It also does not consider differences in race and ethnicity.

Growth charts, a BMI calculator, and explanatory information can be found on the CDC’s website: https://www.cdc.gov/bmi.

Many experts believe mild levels of excess fat don’t notably endanger a person’s health. One study has suggested that a forty-five-year-old man at 20 percent above his healthy weight has a life expectancy only a few months shorter than men his age who fall into the healthy weight category. Moderately overweight women are believed to be less at risk than men.

Where excess weight is distributed around your body, however, could be a significant factor in how seriously your health is at risk. The greatest threat is unhealthy fat around the middle to upper body, surrounding the vital organs.

The Body Roundness Index (BRI)

In June 2024, the medical journal JAMA Network Open published a study about the body roundness index (BRI). The study’s author, Professor Wenquan Niu from the Capital Institute of Pediatrics in Beijing, China, showed that BRI is better at assessing obesity than BMI. Unlike BMI, which only uses height and weight, BRI also considers hip and waist measurements. This provides a more accurate estimate of total and visceral fat, the deep belly fat around organs that poses higher health risks.

Separating Fat from Fat

A nagging problem with efforts to address the obesity problem has been incomplete and sometimes faulty information about what causes it. For example, after nutritionists cited saturated fat as a health culprit in the late 1900s, food companies began reducing saturated fat content in their products. In many cases, they substituted trans fat—which was soon pronounced to be more harmful than saturated fat.

Many people assume that all fat is bad. The reality is that the body needs a certain amount of fat to function. It’s a primary source of energy. It’s vital to cell composition and to your chemical makeup.

Trans fat, however, has been heavily criticized for its role in obesity. Scientists have found that excessive consumption of trans fat can build up cholesterol in the blood and lead to heart disease. Nutritionists suggest that trans fat and saturated fat should account for less than 10 percent of the calories you consume, but many Americans double that amount. Various packaged desserts, french fries, potato chips, greasy burgers, and pastries are high in trans fat. Fast food restaurants in particular have come under fire for the levels of trans fat contained in their fries.

Sweetened, carbonated soft drinks are another primary target in the anti-obesity war because they are high in nonessential sugar content. The average American drinks about twice as much soda today as in the 1980s.