Obesity
Obesity is a chronic condition that occurs when a person has excess body fat that affects health. Obesity isn’t defined by weight alone. Obesity can increase the risk of heart disease, stroke, type 2 diabetes, and other health problems.
Body fat is normal and necessary. However, when the body stores more energy than it uses, fat builds up. Excess fat can affect how your organs work, how your body handles blood sugar, and how your heart and blood vessels function.
Symptoms
Obesity itself doesn’t always cause clear symptoms. You may not notice changes right away. Related health conditions can develop gradually.
Some people may notice:
Increased waist size
Shortness of breath with activity
Joint pain, especially in the knees, hips, or lower back
Low energy or fatigue
Snoring or poor sleep
You may also develop related conditions such as high blood pressure or type 2 diabetes. Children and adults can both have obesity, though health effects may differ by age.
Causes & Risk Factors
Obesity can occur for many reasons. Some causes directly lead to weight gain, while risk factors increase the likelihood of obesity.
Causes
When the body regularly takes in more calories than it burns, it stores the extra energy as fat.
Several factors influence your body weight:
Hormones and brain signals: Some hormones increase hunger, while others signal fullness. In obesity, these signals may not work as effectively.
Genetics: Having close family members with obesity can increase risk, but genes do not determine outcomes on their own.
Daily habits and environment: Large portion sizes, frequent access to highly processed foods, sedentary work, limited activity, poor sleep, and chronic stress can contribute.
Medical conditions and medications: Conditions such as hypothyroidism or polycystic ovary syndrome, and certain medications like some antidepressants, steroids, or insulin, may lead to weight gain.
Risk Factors
Some factors increase the chance of developing obesity.
Modifiable Risk Factors
Physical inactivity
High intake of calorie-dense foods and sugary drinks
Poor sleep habits
Long periods of sitting
Chronic stress
Depression or other mental health conditions
Certain medications
Non-Modifiable Risk Factors
Family history of obesity
Genetics
Hormonal conditions such as polycystic ovary syndrome
Social and Environmental Factors
Limited access to healthy foods
Limited access to safe places for physical activity
Work or living conditions that make healthy choices harder
Diagnosis
Clinicians diagnose obesity using body measurements and medical history.
The most common tool is body mass index, or BMI. BMI uses height and weight to estimate body fat. In adults, a BMI of 30 or higher falls in the obesity range. BMI is a screening tool. It uses height and weight to estimate body fat, but it doesn’t directly measure body fat.
Clinicians may also consider waist circumference, muscle mass, age, and overall health when making a diagnosis. A larger waist size can signal a higher risk for heart and metabolic disease.
For children and teens, clinicians use BMI percentiles based on age and sex.
Clinicians may track weight and related health conditions across visits to guide treatment.
Treatment
The goals of treatment are to improve health, lower the risk of complications, and support weight loss you can maintain. Even modest weight loss can improve blood pressure, blood sugar, and cholesterol levels.
You may not need the same treatment as someone else. Care depends on overall health, weight-related conditions, and personal goals.
Lifestyle Changes
Lifestyle changes are the foundation of treatment.
Nutrition changes focused on balanced, portion-controlled meals
Reducing sugary drinks and highly processed foods
Increasing physical activity, such as walking, swimming, or cycling
Strength training to build muscle
Improving sleep habits
Behavioral support, such as counseling or structured programs
Long-term lifestyle changes help support lasting weight management.
Medications
Prescription weight-loss medications may help some adults and adolescents with obesity, especially if lifestyle changes alone have not led to enough improvement.
These medications work in different ways. Some reduce appetite. Others help people feel full sooner or affect how the body absorbs fat.
Medications are used along with lifestyle changes, not in place of them. A clinician will review benefits, side effects, and individual health factors before prescribing.
Procedures
Bariatric surgery is an option for some people with severe obesity or obesity with serious health conditions.
Common procedures include:
Gastric bypass
Sleeve gastrectomy
These surgeries change how the stomach and small intestine handle food. They can lead to significant weight loss and improvement in related conditions.
Surgery is not for everyone. It requires long-term follow-up, nutrition monitoring, and lifestyle changes
Living With/Prevention
Obesity is a chronic condition. Long-term care focuses on improving your health, not just your weight.
Regular follow-up visits help monitor blood pressure, blood sugar, cholesterol, and other risk factors. Adjustments to treatment may be needed as health changes.
Prevention strategies include:
Eating regular, balanced meals
Choosing whole foods such as vegetables, fruits, lean proteins, and whole grains
Limiting sugary drinks and highly processed snacks
Staying physically active most days of the week
Getting enough sleep
Reducing screen time when possible
Support from healthcare professionals, family, and community programs can help. Sustainable habits and ongoing care can improve health at any weight.
Learn how obesity is treated and managed
Explore practical steps, treatment options, and daily habits that support healthy weight and long-term health.
References
Elmaleh-Sachs A, Schwartz JL, Bramante CT, et al. Obesity management in adults: A review. JAMA. 2023;330(20):2000-2015. doi:10.1001/jama.2023.19897
National Heart, Lung, and Blood Institute. Symptoms and diagnosis. Overweight and obesity. Accessed February 27, 2026.
National Heart, Lung, and Blood Institute. Treatment. Overweight and obesity. Accessed February 27, 2026.
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