What causes obesity?

Obesity can occur over time if you take in more calories than you use. This may happen as a result of overeating, not getting enough physical activity, or both. Other factors may make it harder to lose weight, such as menopause, being on certain medications, insufficient sleep, high amounts of stress, and genetics.  

Definition of Obesity

Experts use body mass index (BMI) to determine how healthy a person’s weight is. Obesity is defined as having a BMI of 30 or higher. If your BMI is 25-29.9, you are considered overweight. A healthy BMI is between 18.5 and 24.9. There are more factors than BMI that are taken into consideration when determining a healthy weight for each person, but BMI is a good place to start. Calculate your BMI.

Obesity as a Cause of Disease

A person with obesity has a greater risk of several diseases and health conditions. Achieving and maintaining a healthy weight may help you not only feel better, but also reduce your chance of developing serious health issues.

Cardiovascular disease

Having obesity has been directly linked to an elevated risk of heart disease, stroke, and other diseases of the blood vessels. Increased body fat can cause atherosclerosis (buildup of plaque in the arteries) and lead to hypertension (high blood pressure), high blood cholesterol and triglycerides (hyperlipidemia), enlarged heart, and blood clots.


According to the American Cancer Society, about 5% of cancers in men and 11% in women may be due to being overweight. Having excess body weight has been linked to a raised risk of endometrial, esophageal, liver, stomach, kidney, pancreatic, colorectal, gallbladder, ovarian, breast, and thyroid cancers, as well as multiple myeloma (cancer of the bone marrow) and meningioma (a type of brain tumor).


Having excess body weight increases your risk of type 2 diabetes, which is a risk factor itself for diseases such as heart disease, stroke, peripheral vascular disease, kidney failure, and eye problems.

Fatty liver disease

Obesity is the leading cause of nonalcoholic fatty liver disease (NAFLD), which is now the most common liver disease in the United States. Left unmanaged, NAFLD can progress to cirrhosis (scarring of the liver). It is becoming a leading reason for liver transplantation in this country.

Gastroesophageal reflux disease (GERD)

Obesity, especially increased body fat around the abdomen, can cause gastroesophageal reflux disease (GERD), which causes heartburn and other discomfort. If not treated well, GERD raises the risk of erosive esophagitis (inflammation of the esophagus), Barrett’s esophagus (a thickening of the esophagus which can be a precursor of cancer), and esophageal cancer.

Sleep disorders

People who have obesity have a greater chance of experiencing poor sleep quality and obstructive sleep apnea, a disorder that causes interruption of breathing during sleep and can result in poor attention and performance during the day. Sleep apnea also raises the risk of cardiovascular disease.


Obesity is the leading cause of osteoarthritis—the kind of “wear-and-tear” arthritis that can develop as you age, but is also made worse by excess weight. Carrying too much weight causes inflammation and can result in pain in your joints and back. Being just 10 pounds overweight places an extra 15 to 50 pounds of pressure on your knees. Having obesity increases the likelihood of needing a knee or hip replacement.

Skin problems

People who have obesity are more likely to experience skin friction, skin infections, and impaired wound healing.

COVID complications

Studies have linked obesity to more severe COVID infection, even in those with no other health problems. People with obesity (especially those with a BMI greater than 40) who contract COVID are more likely to be admitted to the hospital for care, more likely to require critical care (such as ventilation and dialysis), and more likely to die from COVID.

The Health Benefits of Weight Loss

Attaining and maintaining a healthy weight has a number of extraordinary benefits that go beyond looking better in front of the mirror and feeling better in your clothes. If you have excess weight, the health benefits of weight loss include:

  • Reducing your risk of illnesses such as heart disease, stroke, fatty liver disease, GERD, and certain cancers.
  • Less chance of developing type 2 diabetes and if you already have it, better management of your blood glucose and even possible resolution of type 2 diabetes or prediabetes.
  • Lowering your blood pressure, cholesterol, and triglycerides.
  • Decreasing your risk of COVID complications, should you get infected.
  • Better sleep and resolution of sleep apnea.
  • Reduction of arthritis symptoms through less stress on your joints, resulting in less back pain and more comfortable mobility.
  • Healthier skin and faster wound healing.

Why Choose Us

If you or someone you love is struggling with excess weight, you may have questions about the link between carrying too much weight and health problems and how you can take better care of yourself. NewYork-Presbyterian Hospital understands your concerns and provides guidance on how to get to a healthy weight. When you come to us for weight loss treatment, we carefully assess your personal needs and match you with the care that is most likely to help you reach your goals.

Our specialists provide care based on the latest medical evidence, including dietary guidance, behavioral modification, medication, or surgery. Whether you are a new patient or an existing NewYork-Presbyterian patient, our weight management experts are available to help you start feeling better and improving your health. Make an appointment today.