Asian individuals with a Body Mass Index (BMI) of 23 or higher may be more susceptible to health problems.

BMI provides a reasonable estimate of body fat for most people, but it doesn't directly measure body fat. For instance, some athletes with large muscle mass may fall into the obesity category on the BMI scale, even though they don't have excess body fat.

Many healthcare professionals also measure waist circumference to help guide treatment decisions. This measurement is known as waist circumference. Health issues related to excess weight are more common in men with a waist circumference greater than 40 inches (102 cm). They are even more common in women whose waist circumference exceeds 35 inches (89 cm). Other measurements, such as body fat percentage, can also be used during a weight loss program to track progress.

When to See a Doctor

If you are concerned about your weight or weight-related health issues, consult healthcare professionals about how to manage obesity. You and your healthcare team can assess health risks and discuss weight loss options.

Causes

Although genetic, behavioral, metabolic, and hormonal factors affect body weight, obesity occurs when you consume more calories than you burn through daily activities and exercise. The body stores these excess calories as fat.

Most diets in the United States contain an excess of calories, often from fast food and high-calorie beverages. People with obesity may consume larger amounts of calories to feel full, feel hungry more quickly, or eat more due to stress or anxiety.

Many people in Western countries work in jobs that require little physical effort, so they often don’t burn many calories during work. Even daily activities burn fewer calories due to modern conveniences like remote controls, escalators, online shopping, and drive-thru services at restaurants and banks.

Risk Factors

Obesity often results from a combination of causes and contributing factors:

Genetic Factors and Their Effects
Inherited genes from parents can affect the amount of fat your body stores and where it is distributed. Genetic traits may also play a role in how efficiently your body converts food into energy, regulates your appetite, and burns calories during exercise.
Obesity is often passed down through generations in families, not only due to shared genes but also because family members tend to share similar eating habits and physical activity levels.

Lifestyle Choices

• Unhealthy Diet: A high-calorie diet lacking fruits and vegetables, filled with fast food, high-calorie drinks, and oversized portions contributes to weight gain.

• Liquid Calories: People may consume large amounts of calories without feeling full, especially from alcoholic beverages. Other high-calorie drinks, such as sugary sodas, also contribute to weight gain.

• Lack of Physical Activity: If your lifestyle is sedentary, it’s easy to consume more calories than you burn through exercise and daily activities. Spending long hours in front of screens, such as computers, tablets, and phones, is a common example of inactivity and is strongly associated with weight gain.

• Medical Conditions and Medications: Obesity in some people may be linked to medical conditions such as hypothyroidism, Cushing's syndrome, and Prader-Willi syndrome, among others. Health problems like arthritis may also lead to reduced activity, contributing to weight gain.

Social and Economic Factors
Social and economic factors are linked to obesity. It can be difficult to avoid obesity if you lack safe places to walk or exercise, haven’t learned healthy cooking methods, or have limited access to healthy food. Also, the people you spend time with may influence your weight. If you have friends or relatives who are obese, you’re more likely to become obese as well.

Age
Obesity can occur at any age, even in young children. However, as people age, hormonal changes and less active lifestyles increase the likelihood of obesity. As people age, muscle mass often decreases, which lowers metabolism. This makes it more difficult to control weight and increases the risk of weight gain.

Other Factors

• Pregnancy: Weight gain is common during pregnancy, and some women find it difficult to lose this weight after childbirth, which may contribute to obesity.

• Quitting Smoking: Quitting smoking is often associated with weight gain, which can be significant enough to be classified as obesity. This often happens when people turn to food to cope with withdrawal symptoms. However, the benefits of quitting smoking generally outweigh the drawbacks. Healthcare providers can help you manage weight gain after quitting smoking.

• Lack of Sleep: Not getting enough sleep can lead to hormonal changes that increase appetite, especially for high-calorie foods.

• Stress: Several external factors affecting mood and mental health can contribute to obesity. People often eat more high-calorie foods when they are under stress.

• Gut Microbiome: The composition of gut bacteria is influenced by what you eat, and it may contribute to weight gain or make it harder to lose weight.

Having one or more of these risk factors does not necessarily mean you will develop obesity. Most risk factors can be managed through healthy eating, physical activity, and exercise. Behavioral changes, medications, and surgical interventions can also help manage obesity.

Complications
People with obesity are at higher risk for several serious health problems, such as:

• Heart Disease and Strokes: Obesity increases the likelihood of high blood pressure and high cholesterol levels, which are risk factors for heart disease and strokes.

• Type 2 Diabetes: Obesity affects how the body uses insulin to control blood sugar, increasing the risk of insulin resistance and diabetes.

• Certain Types of Cancer: Obesity can increase the risk of cancers of the uterus, cervix, endometrium, ovary, breast, colon, rectum, esophagus, liver, gallbladder, pancreas, kidneys, and prostate.

• Digestive Problems: Obesity increases the likelihood of digestive issues like heartburn, gallbladder disease, and liver problems.

• Sleep Apnea: People with obesity are more likely to suffer from sleep apnea, a serious condition where breathing stops and starts during sleep.

• Osteoarthritis: Obesity increases pressure on weight-bearing joints and leads to more inflammation, swelling, pain, and heat in the body. These factors can contribute to complications like osteoarthritis.

• Fatty Liver Disease: Obesity increases the chances of developing fatty liver disease, a condition caused by excess fat accumulation in the liver. In some cases, this can progress to serious liver damage known as cirrhosis.

• Severe Symptoms with COVID-19: Obesity increases the likelihood of severe symptoms when infected with COVID-19. People with severe cases may require treatment in intensive care units or may need ventilators.

Quality of Life

Obesity can lead to a general decline in quality of life. You may become unable to engage in physical activities you once enjoyed. You might avoid appearing in public, and people with obesity may face negative discrimination.

Other weight-related issues that can affect your quality of life include:

• Depression

• Disability

• Feelings of embarrassment and guilt

• Social isolation

• Reduced productivity at work