Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. A body mass index (BMI) over 25 is considered overweight, and over 30 is obese. In 2019, an estimated 5 million noncommunicable disease (NCD) deaths were caused by higher-than-optimal BMI.

Rates of overweight and obesity continue to grow in adults and children. From 1990 to 2022, the percentage of children and adolescents aged 5–19 years living with obesity increased four-fold from 2% to 8% globally, while the percentage of adults 18 years of age and older living with obesity more than doubled from 7% to 16%.

Obesity is one side of the double burden of malnutrition, and today more people are obese than underweight in every region except the South-East Asia Region. Once considered a problem only in high-income countries, today some middle-income countries have among the highest prevalence of overweight and obesity worldwide.

More than a billion people are living with obesity around the world. This includes about 880 million adults and 159 million children, according to 2022 data. The highest rates are in Tonga and American Samoa for women and American Samoa and Nauru for men, with some 70-80% of adults living with obesity.

Obesity can increase the risk of developing many serious health conditions, including heart disease, type 2 diabetes and some cancers. Ranking global obesity rates (the percentage of population classed as obese, after age differences are accounted for), researchers found:

• China is 11th lowest for women and 52nd lowest for men.
• The US comes 10th highest for men and 36th highest for women.
• India ranks 19th lowest for women and 21st lowest for men.

Obesity in the U.S.

Obesity rates have more than doubled in adults and children since the 1970’s. While some recent estimates suggest that the overall rates of obesity have plateaued or even declined among certain groups, obesity is widespread and continues to be a leading public health problem in the U.S. In addition, severe obesity is a serious and increasing problem among children, adolescents, and adults. Substantial disparities also exist based on race-ethnicity, gender, age, geographic region, and socioeconomic status.

The prevalence of obesity among U.S. adults 20 and over was 41.9% during 2017–March 2020. During the same time, the prevalence of severe obesity among U.S. adults was 9.2%. This means that more than 100 million adults have obesity, and more than 22 million adults have severe obesity. The prevalence of obesity increased from 30.5% in 1999-2000 to 41.9% in 2017–March 2020. During the same time, the prevalence of severe obesity increased from 4.7% to 9.2%.

Many adults with obesity have other serious chronic diseases. For example, 58% of U.S. adults with obesity have high blood pressure, a risk factor for heart disease. Also, approximately 23% of U.S. adults with obesity have diabetes.

Health care for obesity is expensive for patients and the health care system. In 2019, annual medical costs for adults with obesity were $1,861 higher per person than adults with healthy weight. For adults with severe obesity, the excess costs were $3,097 per person. This accounts for nearly $173 billion in medical expenditures in 2019.

According to the latest national figures, 18.5% of U.S. children are obese. (Another 16.6% are overweight and 5.6% are severely obese.) Obesity rates tend to be higher and have increased more rapidly over time among Black and Hispanic children than White children. The prevalence also is higher among children living in rural areas.

Healthcare providers can diagnose obesity based on body mass index (BMI), waist circumference measurements, and other symptoms. BMI factors in someone’s height, body weight, age group, and sex. A BMI of 30 or higher often indicates obesity. Moreover, a waist measurement of over 35 inches for women and 40 inches for men may also indicate obesity. Additionally, here are some common symptoms of obesity: 

• Being overweight
• Tiredness
• Joint or back pain
• Low self-esteem/low confidence 
• Snoring
• Increased sweating

Treatment for obesity often involves exercise, new eating habits, nutritional supplementation, medication, and in some cases, surgery.

What causes obesity?

Obesity is thought to be caused by a combination of physical, psychological, environmental, and/or genetic risk factors. Some diseases and medical conditions can also cause or contribute to obesity.

• Lifestyle choices, including eating unhealthy, processed, and fried foods; physical inactivity; and smoking can lead to obesity. 
• A family history of obesity could mean a person stores fat differently and metabolizes food slowly. Both of these factors can contribute to obesity. 
• Social and economic problems shape our health habits. For example, kids who aren’t taught to eat healthily or exercise are more likely to become obese. Some studies show that having a low income can contribute more to obesity because of a lack of resources to buy healthier foods.
• Underlying medical conditions, like polycystic ovary syndrome or Cushing’s disease, can contribute to weight gain and obesity.

The U.S. Department of Agriculture (USDA) reports that the average American ate almost 20% more calories in the year 2000 than they did in 1983, thanks, in part, to a boom in meat consumption. Today, each American puts away an average of 195lbs of meat every year, compared to just 138lbs in the 1950’s. Consumption of added fats also shot up by around two thirds over the same period, and grain consumption rose 45% since 1970.

Research published by the World Health Organization found that a rise in fast food sales correlated to a rise in body mass index, and Americans are notorious for their fast-food consumption ― such food makes up about 11% of the average American diet. Another study demonstrates the full effect added sugars from soda and energy drinks are wreaking havoc on American waistlines. So it is not just how much we eat, but what we eat.

The role of diet in the U.S. obesity epidemic is obviously major, but it’s also complex. Consumers are sent wildly mixed messages when it comes to what to eat and how much. On one hand, larger portions, processed packaged food, and drive-thru meals are branded as almost classically American — fast, cheap, filling and delicious. On the other hand, we spend over $20 billion annually on weight loss schemes, from diet books and pills all the way up to last-resort surgeries like lap-bands and liposuction. It’s no wonder we’re looking for fast food and fast weight loss options, we spend more time at work and less time in our homes and kitchens than our parents did. Sometimes you only have time to pack a leftover pizza slice and a slim-fast for lunch, irony be damned.

This schizophrenic relationship with food is easy to explain in terms of marketing schemes. As decades of soda and TV dinners caught up with our waistlines, the U.S. diet industry grew bigger, faster and smarter. Since the 1970s, popular nutrition wisdom and fad diets have flamed in and out just as quickly as the Arch Deluxe or the McRib. In the 1990s, our big enemy was fat. Low-fat and fat-free products flew off supermarket shelves. It took us decades to learn that when something is fat-free and full-flavored, it’s probably too good to be true.

As it turns out, most food companies were just swapping hydrogenated oils and sugar in for the animal fats they removed from low-fat products. Hydrogenated oils are restructured vegetable oils that carry high levels of trans-fats, an amazingly evil type of fat that can raise your bad cholesterol, lower your good cholesterol and increase your risks of developing heart disease, stroke and diabetes. While somewhat less sinister, added sugar can also wreak major damage on a diet. Technically low in calories, high-quantities of sugar disrupts our metabolisms, causing surges in insulin and energy levels and ultimately contributing to weight gain and diabetes.

Lack of exercise is also a major culprit in the obesity epidemic. It’s been decades since most Americans worked in fields and on factory floors, a far greater majority of us are sitting throughout our workday. This means less exercise each day. According to one study, only 20% of today’s jobs require at least moderate physical activity, as opposed to 50% of jobs in 1960. Other research suggests Americans burn 120 to 140 fewer calories a day than they did 50 years ago. Add this to the higher amount of calories we are packing in, and we get a perfect recipe for weight gain.

But lethargy goes well beyond the workplace. It is also how we get to work and what we do after. Americans walk less than people in any other industrialized country, preferring to sit in cars to get around. And at the end of the day, 80% of Americans don’t get enough exercise, according to the CDC.

A number of other factors are thought to play a role in the obesity epidemic, such as the in utero effects of smoking and excessive weight gain in pregnant mothers. Poor sleep, stress, and lower rates of breastfeeding are also thought to contribute to a child’s long term obesity risk. Of course, these factors are not explicit or solitary causes of obesity, but they are reliable indicators of the kinds of systemic healthcare failures contributing to this crisis.

In the end, though, we can’t lose sight of the big picture. Over the past years, diet fads have come and gone, with people rushing to blame red meat, dairy, wheat, fat, sugar, etc. for making them fat, but in reality, the problem is much simpler. Genetics and age do strongly influence metabolism, but as the CDC points out, weight gain and loss is primarily a formula of total calories consumed versus total calories used.

How to combat obesity?

Obesity is a chronic disease affecting an increasing number of children, teens and adults. Obesity rates among children in the U.S. have doubled since 1980, and have tripled for teens. About 19.7% of children ages 2 to 19 are considered obese, compared with over 41% of adults who are considered obese.

Earlier onset of type 2 diabetes, heart and blood vessel disease, and obesity-related depression and social isolation in children and teens are being seen more often by health care professionals. The longer a person is obese, the more significant obesity-related risk factors become. Given the chronic diseases and conditions associated with obesity and the fact that obesity is hard to treat, prevention is extremely important.

A primary reason that prevention of obesity is so vital in children is because the likelihood of childhood obesity persisting into adulthood increases as the child ages. This puts the person at high risk of diabetes, high blood pressure and heart disease.

Many of the strategies that produce successful weight loss and maintenance help prevent obesity. Improving eating habits and increasing physical activity play a vital role in preventing obesity. Recommendations for adults include:

• Keep a food diary of what you eat, where you were and how you were feeling before and after you ate.
• Eat five to nine servings of fruits and vegetables daily. A vegetable serving is 1 cup of raw vegetables or 1/2 cup of cooked vegetables or vegetable juice. A fruit serving is one piece of small to medium fresh fruit, 1/2 cup of canned or fresh fruit or fruit juice, or 1/4 cup of dried fruit.
• Choose whole grain foods, such as brown rice and whole wheat bread. Don’t eat highly processed foods made with refined white sugar, flour, high fructose corn syrup and saturated fat.
• Weigh and measure food to learn correct portion sizes. For example, a 3-ounce serving of meat is the size of a deck of cards. Don’t order supersized menu items.
• Learn to read food nutrition labels and use them; keep the number of portions you are really eating in mind.
• Balance the food “checkbook.” If you eat more calories than you burn, you will gain weight. Weigh yourself weekly.
• Don’t eat foods that are high in “energy density,” or that have a lot of calories in a small amount of food. For example, an average cheeseburger with an order of fries can have as many as 1,000 calories and 30 or more grams of fat. By ordering a grilled chicken sandwich or a plain hamburger and a small salad with low-fat dressing, you can avoid hundreds of calories and eliminate much of the fat intake.
• Simply reducing portion sizes and using a smaller plate can help you lose weight.
• Aim for an average of 60 to 90 minutes or more of moderate to intense physical activity three to four days each week. Examples of moderate intensity exercise are walking a 15-minute mile or weeding and watering a garden.
• Look for ways to get even 10 or 15 minutes of some type of activity during the day. Walking around the block or up and down a few flights of stairs is a good start.

What are the government efforts to combat obesity?

While researchers say the obesity epidemic began in the U.S. in the 1980s, there has been a sharp increase in obesity rates in the U.S. over the last decade. Nearly 40% of all adults over the age of 20 in the U.S. – about 93.3 million people – are currently obese, according to data published in JAMA in 2018. Every state in the U.S. has more than 20% of adults with obesity, according to the CDC – a significant uptick since 1985, when no state had an obesity rate higher than 15%. Certain states have higher rates than others: there are more obese people living in the South (32.4%) and Midwest (32.3%) than in other parts of the country.

Federal, state and local governments have moved to address obesity in several ways. On the federal level, several programs – such as the Supplemental Nutrition Assistance Program (SNAP), Women, Infants and Children (WIC) Program, Child and Adult Care Food Program (CACFP) and the Healthy Food FInancing Initiative – as well as the U.S. Departments of Agriculture and Health and Human Services work to make healthier foods affordable and available in under-served communities. To prevent childhood obesity in particular, there are also school and early childhood policies, such as Head Start – a comprehensive early childhood education program – school-based physical education and Safe Routes to School, which promotes walking and biking to and from school and increasing healthy eating and physical activity while reducing the risk of obesity.

The American Academy of Pediatrics and the American Heart Association offered several public policy recommendations, including raising the price of sugary drinks, encouraging federal and state governments to limit the marketing of sugary drinks to kids and teenagers, having vending machines offer water, milk and other healthy beverages, improving nutritional information on labels, restaurant menus and advertisements, and supporting hospitals in establishing policies to discourage the purchase of sugary drinks in their facilities.

Meanwhile, states have implemented laws, largely through early childhood education settings, to improve access to healthy food and increase physical activity in order to promote a healthy weight. These policies stretch from breastfeeding, providing available drinking water and daily physical activity to limited screen time as well as meals and snacks that meet healthy eating standards set by the USDA or CACFP.

Some researchers say there’s little proof that taxing food or drink choices really changes behavior. In spite of taxes and warnings about the health effects of drinking sugary beverages, eight of every 10 American households buys sodas and other sugary drinks each week, adding up to 2,000 calories per household per week, new research shows.

When it comes to suggestions about how to prevent obesity, common principles stand out across local, state and federal guidelines:

• increase physical activity
• improve nutrition through increased consumption of fruits and vegetables
• encourage breastfeeding
• encourage mobility between work, school and communities.

Some researchers also say that the food industry has a role to play in solving the obesity crisis: Making highly processed and fast food much more expensive could curb consumption and lower the obesity rate in the U.S. over time.