Understanding Adult Obesity

THURSDAY, Oct. 8, 2026 (HealthDay News) — Obesity is one of the most common health conditions in the world and one of the most misunderstood. Today, it affects about 4 in 10 U.S. adults, and the numbers keep rising. For a long time, people thought obesity was simply about willpower. But modern medicine tells a different story: Obesity is a long-term, relapsing, complex disease shaped by your biology, your genes and the world around you. Understanding what obesity really is and letting go of the blame is the first step toward better health for millions of people.What Is Obesity?Obesity means your body has too much fat mass, and that fat is not just sitting there. Excess fat is biologically active. It releases hormones and inflammatory signals that contribute to metabolic disorders, inflammation and illness throughout the body. The sheer weight of extra fat also strains joints and other tissues, adding to problems like osteoarthritis and sleep apnea.Doctors usually measure it using body mass index (BMI) — an estimate of body fat based on your weight and height. Here is how the categories break down:Overweight: BMI 25 to 29.9Obesity, Class 1: BMI 30 to 34.9Obesity, Class 2: BMI 35 to 39.9Obesity, Class 3 (severe): BMI 40 or higherBMI is not perfect. It does not measure fat directly, so it can be off for people who are very muscular or who have low muscle mass. Because of this, your doctor may also measure your waist to provide a fuller picture. If you are of Asian descent, health risks such as diabetes and heart disease, can show up at a lower body weights, so doctors may use a lower BMI cutoff of 27.5 or even 25 to classify obesity and start prevention strategies early.Symptoms of ObesityObesity is defined by extra body fat, not by a single symptom. But it often causes changes you can feel and see, such as:Extra body fat, especially around the belly (which poses the greatest health risk)Shortness of breath during everyday activitiesAching jointsSnoring or pauses in breathing during sleep (sleep apnea)Emotional effects, such as low self-esteem, anxiety or depressionReduced quality of life and limits on daily activitiesObesity is also linked to many chronic conditions, including heart disease, type 2 diabetes and several cancers.How Is Obesity Diagnosed?Most people are first diagnosed by their primary care doctor during a regular visit. The process is simple:Measurements: Your height and weight are recorded to calculate your BMI, and your waist may be measured. Some clinics can test body composition to measure percentage of body fat and where the fat is stored using special tools, such as a bioelectrical impedance scale (which sends a tiny, painless electrical signal through the body) or imaging scans.Health history and exam: Your doctor asks about your weight over time, eating and activity, sleep, mood, family history and medications as some drugs cause weight gain.Blood tests: Bloodwork can check for related problems like diabetes, high cholesterol, liver trouble and thyroid issues. If your history points to a less common cause, such as a hormone problem, your doctor may test for that too.Depending on your needs, you may be referred to a specialist, such as an obesity-medicine doctor, an endocrinologist or a bariatric surgeon.How Is Obesity Treated?Because obesity is a long-term condition, treatment focuses on managing it over time. Here is some good news: Losing just 5% to 10% of your body weight can meaningfully improve your blood pressure, blood sugar and overall health. Most treatment plans combine a few approaches:Lifestyle and behavior programs: This is the foundation. This includes diet counseling, increased physical activity, self-monitoring, goal-setting and problem-solving. This usually leads to weight loss of about 5% to 10%.Nutrition: The goal is to eat fewer calories in a way you can stick with. There is no single "best" diet; the right one fits your life and your tastes.Physical activity: Aim for at least 150 minutes of moderate exercise a week. On its own, exercise leads to modest weight loss, but it is very important for keeping the weight off.Medications: A doctor may recommend them alongside lifestyle changes for some patients — those with a BMI of 30 or higher, or those with a weight-related condition and a BMI of 27 or higher. Options approved by the U.S. Food and Drug Administration include the newer injectables semaglutide (Wegovy) and tirzepatide (Zepbound), plus oral phentermine-topiramate (Qsymia), naltrexone-bupropion (Contrave) and orlistat (4). Combined with lifestyle changes, Wegovy and Zepbound can produce significant weight loss, about 15% to 21%.Metabolic and bariatric surgery: This is the most effective option for severe obesity, generally considered at a BMI of 35 or higher (or 30 or higher with related conditions). The two most common procedures — sleeve gastrectomy and Roux-en-Y gastric bypass — produce about 25% to 35% weight loss and can improve or even resolve conditions like diabetes.What Causes Obesity?At the simplest level, obesity develops when your body stores more energy than it burns over a long time. But the reasons behind that are far from simple. Your body carefully controls your weight using hormones and brain signals that manage hunger and fullness. When you lose weight, your body often fights back, making you hungrier and slowing your metabolism. That is one big reason keeping weight off is so hard.Experts point to our modern "obesogenic environment" as a main driver of rising obesity: inexpensive, high-calorie, heavily processed foods are everywhere; portions are large; food ads are constant; work and leisure are more sedentary; sleep is shorter; and stress is higher. These forces build on your own biology — which is why not everyone in the same environment develops obesity.Obesity Risk FactorsGenetics: Inherited genes explain an estimated 60% to 70% of the differences in weight between people, affecting appetite and how the body stores fat.Obesogenic environment: Contributors include easy access to calorie-packed food, few healthy choices and neighborhoods that make walking or exercise hard.Physical inactivity: Sitting for work and leisure means fewer calories burned each day.Poor sleep and ongoing stress: Both throw off appetite hormones and can lead to weight gain.Mental health conditions: Depression and obesity each increase risk of the other.Certain medications: Some medications can cause weight gain.Money and food access: Lower income and unstable food access are linked to higher risk.Living With ObesityObesity is linked to more than 200 health conditions, and problems tend to build over time. Serious long-term risks include:Type 2 diabetesHigh blood pressureHeart disease, strokeSleep apneaOsteoarthritisFatty liver diseaseSeveral types of cancerIt can also lower quality of life and shorten lifespan, especially in severe forms. The good news: Losing weight and getting treatment can prevent, improve or even reverse many of these problems.Just as harmful and talked about far less is weight stigma. If you have obesity, you may face unfair bias at work, in healthcare and in the media. Research is clear that stigma does not motivate weight loss. Instead, it drives stress, depression, anxiety, unhealthy eating and avoidance of both exercise and medical care. Because stigma is likely to drive weight gain and poor health, it should be addressed.Steps that help reduce stigma:Using person-first language: "a person with obesity," not "an obese person"Treating obesity as a medical disease, not a personal failing or a lack of willpowerMaking healthcare settings welcoming, with properly sized equipment and respectful, judgment-free careIncluding people with obesity in decisions about their own careThe bottom line: Obesity is a long-term disease with roots in your biology, and today's treatments are better than ever. Pairing good medical care with compassion and dropping the blame offers the best chance to improve your health and feel your best.More informationThe U.S. Centers for Disease Control and Prevention has more on obesity.About the expertDr. Vallari Kothari is board-certified in Endocrinology, Obesity Medicine, and Internal Medicine. After earning her medical degree in India, she completed her Internal Medicine residency at Henry Ford Hospital in Michigan and her Endocrinology fellowship at the University of Illinois, Chicago. Prior to joining Montefiore Medical Center in New York City, Dr. Kothari practiced at Griffin Hospital in Connecticut.Her clinical interests include general endocrinology and obesity medicine, with a particular focus on managing complex metabolic disorders, obesity management in younger women and improving health outcomes in diverse patient populations. .Sign up for our weekly HealthDay newsletter

Understanding Adult Obesity

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