Obesity

Obesity is a health condition where a person has too much body fat, which can cause problems for their body. It is considered a disease by many health groups. People are said to have obesity when a special number called their body mass index, or BMI, is above 30. BMI is a way to measure if someone is a healthy weight for their height.

Having obesity can lead to many health issues, like heart problems, diabetes, and trouble sleeping. There are many reasons why someone might become obese, including what they eat, how active they are, their genes, and even where they live.

It can be hard for people to keep weight off once they have lost it. Doctors suggest eating better foods and exercising more to help prevent and treat obesity. Sometimes, special medicines or operations can also help people lose weight. Obesity affects millions of people around the world, both adults and children, and it is more common in women than in men. Some places see obesity as a bad thing, while others have seen it in a more positive way.

Classification

Main article: Classification of obesity

Obesity happens when someone has a lot of extra body fat that can affect their health. Doctors often use something called body mass index (BMI) to decide if someone is obese. BMI is a way to measure if someone’s weight is healthy by dividing their weight by the square of their height.

For adults, the World Health Organization says people with a BMI of 25 or higher are overweight, and those with a BMI of 30 or higher are obese. Some countries, like Japan and China, use different numbers to decide if someone is obese because people in these places can have health problems at lower BMIs.

For children, doctors look at age, height, and weight together to decide if they are obese. This helps because children grow at different rates. There are also other ways to measure health besides BMI, like looking at how much body fat someone has, but BMI is often used because it’s easier to calculate.

Causes

The idea that "a calorie is a calorie" suggests that most obesity happens when people eat more food than they use in activity. Some cases are due to genes, health issues, or mental health conditions. How full we feel after eating can change depending on the type of food.

Obesity rates increase when food is easy to get and tasty, people use cars more, and jobs involve machines. Other ideas for why obesity is increasing include not getting enough sleep, certain chemicals in the environment, some medicines, and changes in temperature. Research is still trying to understand how big each of these factors really is.

Diet

Eating too much tasty, high-calorie food—like fats, sugars, and certain proteins—is a big reason for obesity around the world. This happens partly because of changes in brain chemicals that control hunger and how the body senses nutrients. The amount of calories available to eat has gone up a lot in most places. For example, in the United States, the average person had about 3,654 calories per day in 1996, jumping to 3,754 calories by 2003.

Even with rules about healthy eating, many people still eat too much. From 1971 to 2000, obesity in the United States went from 14.5% to 30.9%. Women added about 335 extra calories per day, and men added about 168. A big part of this came from eating more carbs, especially sugary drinks and potato chips. Drinking sweetened beverages is linked to higher obesity rates and health problems like type 2 diabetes.

As fast food becomes more common, it adds to obesity. In the United States, fast-food eating tripled and the calories from it quadrupled between 1977 and 1995. Government rules like farm policies and food prices make processed foods cheaper than fruits and vegetables. Laws about showing calorie counts try to help people make healthier choices.

People who are obese often say they eat less than they really do. Tests and observations show this is true.

Sedentary lifestyle

Not being active also leads to obesity. Many jobs today need less physical work, and people use cars and machines more. Children also move less because of safety worries, changes in how they play, and places to activity. Watching TV or other screens is linked to higher obesity risk in children.

Genetics

Obesity comes from both genes and the environment. Some gene changes make people more likely to gain weight if they have enough food. By 2006, over 41 gene spots were linked to obesity. People with certain gene versions, like the FTO gene, often weigh more and have a higher chance of obesity.

Obesity is also seen in some health conditions like Prader-Willi syndrome. When both parents are obese, about 80% of their children are obese too, compared to less than 10% if both parents are a healthy weight.

Other illnesses

Some health problems and medicines can raise the risk of obesity. Conditions like hypothyroidism or Cushing’s syndrome can cause it. Certain medicines like some antidepressants, steroids, and some mental health medicines can also lead to weight gain.

Social determinants

How rich or poor someone is can affect obesity rates differently around the world. In some places, richer people are less likely to be obese, while in others, richer people have higher obesity rates. Urban areas, especially in developing countries, often have higher obesity because of less space to walk or play and more time in cars.

Not getting enough sleep and certain personal traits like feeling lonely or having less self-control may also connect to obesity. Global trade and changes in what countries buy and sell can also play a part in rising obesity rates.

Pathophysiology

Main article: Pathophysiology of obesity

Obesity happens when the body gets used to having more food than it needs. Scientists are still learning how this works, but they have found some clues.

The body has special chemicals that help control hunger and how much we eat. These chemicals work in the brain, especially in an area called the hypothalamus. This part of the brain helps decide when we feel hungry and when we feel full.

There are different groups of brain cells that work together to control these feelings. Some cells make us feel hungry, while others help us feel full. When the body doesn't get the right signals, it can lead to eating too much and gaining weight.

Management

Main article: Management of obesity

The main way to treat obesity is to lose weight through changes in daily habits, such as eating special diets and doing more physical activities. Doctors can also use medicines or surgery to help with obesity. While it’s not clear which diets work best for keeping weight off for a long time, making changes to eat fewer calories or move more can help people lose weight, even if they may gain some of it back later.

Keeping weight off for many years can be hard, but some people have managed it with the right plans. In the United States, doctors suggest combining changes in eating habits with more exercise. Different diets can work, but sticking to the plan is more important than which diet you choose. Eating less sugar and following diets like the Mediterranean way may help protect the heart. Changing how we eat during pregnancy can also help both mothers and babies stay healthier.

Health policy

Obesity is a big challenge for public health because it affects many people and costs a lot. Solving it needs help from everyone, including communities, local leaders, and governments. Efforts focus on changing things in our environment that make people eat too much or move too little. This includes making school meals healthier, limiting ads for unhealthy foods to children, and reducing sugary drinks in schools. The World Health Organization suggests taxing sugary drinks. Cities are also trying to create spaces where people can walk more and play outside. Some people also think we should try to reduce foods that are processed and have a lot of extra ingredients.

Public health campaigns can help people learn more about eating well and being active, though they may take time to show results. Showing calorie information on restaurant menus can also help people make healthier choices.

Medical interventions

Medication

Main article: Anti-obesity medication

Since the 1930s, many medicines have been tried to help with obesity. Most of these medicines only help people lose a little weight, and some were stopped because they caused bad side effects. Six medicines are still used for long-term help with weight, but we do not know yet how they affect health problems related to obesity over many years.

Surgery

The best way to treat obesity is through a special kind of surgery. Different types of surgery can help people lose weight and improve health problems related to obesity. These surgeries help people keep the weight off for many years, but sometimes they can have complications and need more surgery later.

Epidemiology

Main article: Epidemiology of obesity

Obesity used to be rare and only found among very wealthy people. But as life got better, especially from the Early Modern period onward, more and more people began to have this condition. Before the 1970s, obesity was still uncommon even in rich countries, mostly affecting the wealthy.

By 1997, health experts declared obesity a worldwide problem. By 2008, over 500 million adults were obese, and by 2022, this number had grown to more than 600 million. In the United States, about 40% of adults were obese by 2015–2016. Some places, like Tonga and Nauru, have very high rates of obesity, with over 60% of adults affected.

Obesity rates are rising in both rich and poor countries, especially in cities. By 2021, nearly half of all adults worldwide were overweight or obese. If these trends continue, most adults may face this issue by 2050. Women are more likely to be affected than men, but this can vary depending on how obesity is measured.

History

Etymology

The word "Obesity" comes from a Latin word meaning "stout, fat, or plump." It was first used in English in the year 1611.

Historical attitudes

Ancient Greek doctors and Egyptian people thought obesity was a health problem. A famous Greek doctor once said that being very heavy was not just a disease but could lead to other health issues. For most of history, people struggled to find enough food, so being overweight was often seen as a sign of wealth and success. This idea lasted in many places, including parts of Africa today.

During the Industrial Revolution, stronger, bigger bodies were important for soldiers and workers. As people got taller and heavier, obesity became more common. In the 1950s, as people got richer, some health problems like heart disease started to appear more often with extra weight.

Many cultures have had different views on obesity. In some ancient plays, heavy characters were made fun of. In Christian times, overeating was sometimes linked to bad behavior. Today, in many Western countries, being overweight is often seen in a negative way, and people can face unkind treatment because of their size.

The arts

Very old statues from thousands of years ago sometimes show larger women, perhaps to highlight fertility. In later times, especially during the Renaissance, some rich and powerful people showed off their larger size in paintings. Over time, ideas about what is considered a beautiful or healthy body shape have changed a lot.

Society and culture

Economic impact

Obesity can cause many problems beyond health issues. It can make it harder for people to find jobs and can cost businesses more money. For example, in the United States, obesity-related medical costs were estimated at $190.2 billion in 2005. In Canada, the cost was about CA$2 billion in 1997.

Some countries have tried to reduce obesity by adding extra taxes to sugary drinks. These efforts aim to help lower the costs that obesity creates for everyone.

Socioeconomic status

In some poorer countries, having more weight can sometimes show that a person has more money. For example, a study in Uganda found that people with more weight were more likely to get loans.

Size acceptance

Many groups work to help people feel better about their size and to stop unfair treatment based on weight. The National Association to Advance Fat Acceptance (NAAFA) in the United States and the International Size Acceptance Association (ISAA) are two such groups. They want everyone to be treated fairly, no matter their size.

Industry influence on research

In 2015, a group called the Global Energy Balance Network suggested that people should focus on exercising more instead of eating less to stay healthy. This group was funded by a big company that sells sugary drinks.

Reports

Many groups have made reports about obesity. In the United States, the first federal guidelines came out in 1998. In Canada, guidelines were published in 2006. The United Kingdom also released important reports in 2004 and 2006, warning about the growing problem of obesity and what can be done to help. In 2022, a big review in the UK looked at what local governments can do to reduce obesity.

Childhood obesity

Main article: Childhood obesity

Keeping a healthy weight is important for children, just like it is for adults. Doctors measure this using something called BMI, which changes as children grow. When a child’s BMI is higher than most other kids their age, they may be considered to have a weight problem.

In recent years, more and more children around the world are having trouble with their weight. This happens in both rich countries and poorer ones. Eating more unhealthy foods and moving less are the biggest reasons for this change. Some other things, like certain medicines given to very young babies, can also play a part. Because keeping a healthy weight matters so much, doctors check for problems like high blood pressure, diabetes, and liver issues in children who are overweight.

There are ways to help children keep a healthier weight, mostly by changing eating habits and encouraging more activity. In the United States, special medicines for weight loss are not approved for children. Doctors and nurses can give advice, but changes work best when families work together on healthy eating and more movement.

Statistics

The Centers for Disease Control and Prevention (CDC) found that about 42% of adults in the United States were obese from 2017 to March 2020. During that time, about 9% of adults had severe obesity. Obesity was least common among non-Hispanic Asian adults at 17%, while it was more common in non-Hispanic white (42%), non-Hispanic black (50%), and Hispanic (45%) adults.

Other animals

Obesity in pets is common in many places. In the United States, between 23% and 41% of dogs have extra weight, and about 5% are obese. For cats, the rate is a bit higher at around 6%. In Australia, about 7.6% of dogs seen by veterinarians are obese. The chance of a dog being overweight can be linked to whether their owner has extra weight, but this is not the same for cats.