What You Need To Know About Obesity

What is obesity?

Obesity is a disease, and it happens when you have excessive body weight. The extra fat in your body can put a strain on your bones and organs. It can also put you at a higher risk of developing certain health conditions like diabetes and stroke.

Obesity is becoming more common worldwide, with 650 million people now considered obese globally. In the United States alone, the CDC reports that 42% of adults in 2017 and 2018 were obese.

While it's difficult to measure body fat, the current method used by doctors is the body mass index (BMI). Your doctor can calculate your BMI based on your height and weight. Anyone with a BMI score of 30 or higher is considered obese. A score of 40 or higher is considered morbidly obese. Being morbidly obese means you could be at an increased risk of developing other health conditions due to your weight, some of which can be life-threatening. 

Obesity doesn't only affect adults. It can affect children and teens, too. In the United States, nearly 20% of children are obese. That's around 14.4 million children and teens in total.

Children and teens are considered obese if they are in the 95th percentile or higher of their weight status category for their age. Children who are obese are more likely to be obese adults and can be at risk of developing obesity-related health conditions later in life.


  • The worldwide rate of obesity has increased 300% since 1975¹

  • 42.4% of adults in the United States are considered to be obese²

  • 19.3% of children and teens in the United States are obese³

  • 9.2% of adults in the United States are considered severely obese²

  • Health care costs for obesity and obesity-related illnesses totaled $147 billion in 2008²

  • Obesity kills more people worldwide than being underweight¹

  • Obesity is more common in Black and Hispanic households²

  • One in four Hispanic children are considered to be obese³

  • Obesity is associated with at least 13 different types of cancer⁴

  • Obesity kills at least 2.8 million people each year⁵

  1. Obesity and overweight | World Health Organization

  2. Adult obesity facts | Centers for Disease Controls and Prevention

  3. Childhood obesity facts | Centers for Disease Controls and Prevention

  4. Cancer and obesity | Centers for Disease Controls and Prevention

  5. Obesity statistics | The European Association for the Study of Obesity


At its most basic, obesity is caused by taking in more calories than your body uses. Over time, your body turns the extra calories into body fat and stores it to use as energy in the future. If you don't burn the energy reserves, the fat stays in your body. Storing too much fat can cause you to become obese.

While caloric intake plays a very important role in the development of obesity, there are many other complicated factors that can cause or increase the risk of obesity. 

Known or suspected causes of obesity

Mental health

Stress, anxiety, and mental health struggles can lead you to eat more than normal or eat to comfort yourself. Learning healthy coping mechanisms or getting therapy may help you take control of your weight.

Activity levels

If you don't live a very active lifestyle, you may be at risk of obesity. Sedentary lifestyles have little activity and may be due to working a desk job or enjoying hobbies like video games. One study found that TV viewing, a very passive pastime, was consistently related to having a higher BMI.¹

Hormone imbalances

Your brain relies on hormones to tell it when you are hungry or full. If those hormones are not working correctly, you might not get the signal that you are full and to stop eating. Or you might feel hungry when you are not. That can lead to consuming more calories than your body uses.


Some medications can cause you to feel hungry more often. Others might slow down your metabolism, meaning you'll burn calories at a slower rate. They can also cause your body to store more sugar or water, leading to weight gain even without the addition of fat.


You may be predisposed to weight gain based on your genetics. Your genes can dictate factors such as your metabolism, your body's ability to store fat, or when and how often you feel hunger.

Socioeconomic factors

Sometimes it's harder to eat healthily because of where you live or the amount of money you have. One study found that healthy foods were twice as expensive as unhealthy foods.² Healthy foods may be less available in some areas, too. In those same places, fast food might be readily available, with plenty of inexpensive but high-calorie options.

Risk factors for developing obesity

Anyone can become obese if they consume more calories than they use over a long period. However, certain factors could increase your risk of becoming obese, including:


Those who live sedentary lifestyles are at an increased risk of becoming obese. Being sedentary means you aren't active, and it's a common lifestyle issue for many Americans. Working a desk job, watching TV, or playing video games are all things that can lead to a sedentary lifestyle. It's important to counteract an inactive lifestyle by getting at least 30 minutes of exercise a day.

Family history

If your parents were obese, you are at a higher risk of being obese, too. That could be due to genetics, learned behaviors, or a combination of the two.


Older people are more at risk of becoming obese, thanks to a slowing of the metabolism as they age. Black and Hispanic adults have also been found to have an increased risk of becoming obese.³ 

Health complications caused by obesity

Obesity is a serious health concern. It can decrease the quality of life while also putting strain on your body's internal systems. It's associated with an increased risk for health conditions, such as:

  • Diabetes

  • Stroke

  • Heart disease

  • Some types of cancer

  • Osteoarthritis 

  • Sleep apnea

  • Fertility and pregnancy issues

  • Depression and anxiety

Some of these health concerns can be life-threatening. Even moderate weight loss can help reduce your risk of developing health conditions such as these and ease the strain on your internal organs and joints. Losing 5–10% of your body weight can significantly improve your health.


The treatment for obesity involves losing weight. That means eating fewer calories and expending more calories through exercise and activity. When your body doesn't have the calories it needs for your daily activities, it will tap into your fat reserves and convert that fat into energy.

However, it's rarely easy for people to achieve or maintain a calorie deficit and lose weight on their own. A healthcare provider can work with you to develop a personalized weight loss plan based on your age and lifestyle. Weight loss plans should be personalized to the individual for the best results. Your plan might include weight loss medication, surgical intervention, or comprehensive lifestyle and behavioral changes. 

Weight loss medications

Common weight-loss medications include Contrave, Saxenda, and Xenical. These medications can work in various ways, including reducing your hunger or reducing fat absorption in your gut. These medications can cause side effects, including nausea, vomiting, diarrhea, and dizziness.

The effectiveness of these medications may decrease over time, and stopping the medication may result in weight gain. It's important to work closely with your doctor while taking these medications to ensure you have a diet and exercise routine in place that will support a healthy weight without the help of medication in the future.

Medications for weight loss won't work on their own. You'll need to take them while also making improvements to your diet and increasing your activity levels.  

Weight-loss surgeries

In some cases, your doctor may recommend weight-loss surgery to help you rapidly lose weight. These surgeries don't remove any fat. Instead, they restrict the amount of food you are able to eat. That limits the number of calories you can consume, allowing your body to use the calories stored in your fat reserves.

Most weight-loss surgeries involve reducing the size of the stomach. These include:

Endoscopic procedures

These surgeries don't require incisions. Instead, once you are sedated, a doctor will use flexible tubes inserted down your throat to access your stomach to do the procedure. They may place a stitch or inflate a small balloon with water inside the stomach to limit the amount of food your stomach can hold.

Adjustable gastric banding

A surgeon will place an inflatable, belt-like device around your stomach, reducing the amount of food your stomach can hold. The food then passes through a narrow channel left by the band and enters the intestine.

Gastric sleeve

This procedure involves removing part of the stomach to make it smaller and reduce the space for food.

Gastric bypass (Roux-en-Y) surgery

This is another, more complicated, surgical option for weight loss. During gastric bypass surgery, your doctor creates a small pouch in the top of your stomach, then re-routes your small intestine to this smaller pouch. This limits the amount of time food spends in your stomach, and thus, how many calories your body can take in from the food that's there.

For any weight-loss surgery to be successful, you have to make a life-long commitment to changing your diet and lifestyle. If you go back to your old habits, you can undo any weight loss you achieved and could even gain additional weight. 

Lifestyle and behavioral changes

Making small lifestyle changes can result in weight loss. Your healthcare provider can help you determine good lifestyle and behavioral changes to support healthy weight loss. These might include:

  • Cooking meals at home instead of eating out

  • Increasing the quality and duration of your sleep

  • Reducing food/meal portions

  • Learning which foods support healthy weight loss

  • Understanding what foods to limit and why

  • Tracking your food intake through a food diary or app

  • Incorporating physical activity into your daily life

  • Getting support from a trusted network of family and friends

Making sustainable lifestyle and behavioral changes is key to losing weight and keeping it off. Find healthy foods you enjoy eating and activities that you look forward to doing. Over time, these changes become habits, and those healthy habits lead to long-term weight loss and weight loss maintenance.


Obesity is a preventable disease. You play an important role in this prevention. There are also big changes that need to happen within society to help others avoid becoming obese.

As an individual, you can limit your calorie intake. This means learning more about good nutrition and what foods fuel your body without excess calories and sugar. Increasing your consumption of fruits, vegetables, and whole grains is a good place to start. You'll also want to increase your daily activity. Find hobbies and interests that get you up and moving around to avoid a completely sedentary lifestyle.

There is also a lot that can be done within society to prevent obesity. Food manufacturers can limit the number of calories in processed foods. Governments and charities can ensure that neighborhoods have access to plenty of affordable, healthy food options. Doctors can educate patients on nutrition and diet. Employers can even play a role by offering incentives to exercise.

Nearly three million people die each year as a result of obesity.¹ Promoting healthier foods, more active lifestyles, and obesity risk awareness can help bring that number down.

  1. Obesity statistics | The European Association for the Study of Obesity

Doctors & specialists

There are healthcare providers specializing in treating obesity, called bariatricians or bariatric healthcare providers. Bariatric healthcare providers may also be surgeons who specialize in bariatric or weight-loss surgery. However, your regular physician is also able to diagnose and treat obesity. To do so, they may run a variety of health checks, including:

Calculating your BMI

While this can be a flawed measurement of body fat percentage, it can be a useful tool. Your BMI can help your doctor determine where you fall on the scale between being underweight and being obese and help tailor a weight-loss plan to your needs.

Measuring your waist circumference

Fat around your waist can be particularly dangerous as it correlates with excess fat around your abdominal, internal organs.

Ordering lab tests

These tests can check your blood sugar, cholesterol, and thyroid levels and look for indicators of other health concerns. 

Once diagnosed, you can work with your doctor or bariatrician to develop an obesity treatment plan. They may also recommend you see a nutritionist or other specialists for additional advice and monitoring.


Can obesity be genetic?

Genetics can play a role in the development of obesity. Some genetic conditions directly cause obesity, such as Prader-Willi syndrome. However, more commonly, genetics increase or decrease your risk of becoming obese. You may be more predisposed to overeating, storing fat, or leading a sedentary lifestyle based on your genetics.

In this case, your behavior and lifestyle will dictate whether you become obese. For example, you may be genetically predisposed to storing fat, but if you lead an active lifestyle and stick to a healthy diet, you may not become obese.

Are obesity and being overweight the same thing?

There is a difference between being overweight and being obese. Medically, that difference is determined by your BMI. By calculating your BMI, you can determine whether you are obese or overweight:

  • Underweight: below 18.5

  • Healthy: 18.5–24.9

  • Overweight: 25–29.9

  • Obese: 30–39.9

  • Morbidly Obese: 40+

While being overweight can still increase your risk of developing certain health conditions, those risks aren't as serious as they would be if you were obese. The risks become even more severe and may start impacting your quality of life if you are morbidly obese.

Can you develop obesity without overeating?

Overeating is the most common cause of weight gain. However, that's not the only reason. Some genetic conditions can cause obesity. There are also some medications that can increase your appetite or reduce the rate at which your body burns calories.

Genetics can play a big role in your body shape and size and whether you are predisposed to becoming obese. However, even if your genetics increase your risk of becoming obese, your behavior will determine whether it actually happens. In that case, a sedentary lifestyle and overeating can cause you to become obese.

Can obesity be 'cured'?

Obesity is treatable and preventable. With lifestyle and behavior changes, over time, many people are able to lose weight. The healthiest way to cure obesity is to have slow, steady weight loss over a long period of time. With a big enough weight reduction, you may no longer have a BMI that puts you in the obese category. It takes lifelong dedication to a healthy diet and exercise to lose weight and keep it off.

Curing obesity globally is also possible, but it will require massive societal changes. Portion sizes and caloric intake have increased in the last few decades, so it's easier than ever to consume more calories than you need. There will have to be big changes in the food industry to bring obesity to an end globally.

Clinical trials for obesity

Actively recruiting
Cardiovascular Disease & Type 2 Diabetes Study
Actively recruiting
Assessing an Investigational Medication on Major Adverse Cardiovascular Events Such as Heart Attack and Stroke
Actively recruiting
Investigational Weight-Loss Drug Study: Evaluating the Impacts on Cardiovascular Health