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Diseases & Conditions
Obesity
A reliable guide to the causes of obesity, health risks, BMI, lifestyle measures, medications, and surgical options.
Obesity is a chronic disease characterized by an excessive accumulation of body fat that can adversely affect health. Although it is often used as a synonym for being “overweight,” obesity is a broader and more multifactorial condition than that. Eating patterns, physical activity, sleep, medications, psychosocial factors, hormones, genetic predisposition, and environmental conditions may all play a role together. For this reason, explaining obesity solely as a lack of willpower is both scientifically inadequate and stigmatizing. [1][2][3]
How is obesity defined?
In adults, the most commonly used practical measure is body mass index (BMI). The WHO defines a BMI above 25 as overweight and above 30 as obesity. However, BMI is not a perfect measure on its own; it should be interpreted together with muscle mass, waist circumference, fat distribution, and coexisting diseases. In other words, two people with the same BMI may have different levels of metabolic risk. For this reason, the clinical approach should focus not only on the number on the scale, but also on the overall effect on health. [1][2]
Obesity is now an important global public health problem. The WHO emphasizes that obesity and overweight are associated with many noncommunicable diseases. Type 2 diabetes, hypertension, cardiovascular disease, fatty liver disease, sleep apnea, osteoarthritis, and certain cancers are among the most important examples. In addition, obesity can affect mobility, pain levels, mental health, fertility, and quality of life. [1][2][4]
What causes obesity?
Obesity is often described as the result of an imbalance between energy intake and energy expenditure, but in clinical practice the picture is more complex. Easy access to inexpensive high-calorie foods, a sedentary lifestyle, sleep deprivation, stress, certain psychiatric and neurologic conditions, some medications such as corticosteroids, and genetic predisposition all play important roles. Some people may gain weight more easily even under similar living conditions. For that reason, the management of obesity requires an approach that tries to understand the individual causes rather than using blaming language. [1][2][3]
Obesity that develops in childhood may continue into adulthood; however, obesity that begins later in adult life is also very common. If there is rapid weight gain, menstrual irregularity, marked fatigue, purple striae on the skin, or other findings suggesting a clear hormonal disturbance, secondary causes may also be evaluated. Not every increase in weight is caused by a hormonal disease; nevertheless, a proper history and examination are needed for differential diagnosis. [2][3]
What are its effects on health?
One of the most important aspects of obesity is that it increases the risk of long-term complications. MedlinePlus and WHO sources draw attention to outcomes such as type 2 diabetes, heart disease, kidney disease, certain cancers, and respiratory problems. In addition, because of increased joint loading, knee and hip pain, reflux, sleep apnea, daytime fatigue, and increased depressive symptoms may occur. However, the degree of risk varies from person to person; assessment should always be individualized. [1][2][4]
In health assessment related to weight, asking only “how many kilograms should be lost?” is not enough. Waist circumference, blood pressure, blood glucose, lipid profile, liver status, sleep quality, and functional capacity should all be considered together. This is because the goal of treatment is not merely a change in appearance, but reduction of health risk and achievement of sustainable well-being. In some people, a reduction of even about 5% to 10% of initial body weight can produce meaningful improvement in metabolic risks. [3][4]
What is the treatment approach?
Treatment of obesity is multilayered. Healthy dietary patterns, increased physical activity, behavior change, and regular support form the basis of most treatment plans. The NIDDK emphasizes that structured programs and follow-up support may be helpful in maintaining weight loss. However, the recommendation to “just eat less and move more” is often not enough on its own; sleep patterns, stress management, trigger-related eating behaviors, and environmental barriers also need to be addressed. [2][3]
In some people, medication treatment or metabolic-bariatric surgery may also be considered. This decision is made according to BMI, coexisting diseases, the outcome of previous interventions, and an individualized risk-benefit assessment. Surgery is not appropriate for everyone, and medications are not miraculous solutions on their own. It should also be remembered that weight may return when treatment is discontinued; for this reason, long-term follow-up should be planned. Because obesity is a chronic disease, a sustainable approach is more valuable than short-term restrictive diets. [2][3]
If there is shortness of breath, chest pain, rapidly developing edema, signs of very high blood glucose, severe snoring with daytime sleepiness, or pain that seriously limits mobility, medical evaluation should not be delayed. The aim in obesity treatment is not to shame the person, but to reduce health risks. When realistic goals, supportive follow-up, and evidence-based options are combined after individualized assessment, meaningful and lasting improvement can be possible. [1][2][3]
One of the most common mistakes in obesity management is turning to highly restrictive plans that promise rapid results. Very low-calorie and unsustainable diets may lead to initial weight loss but often result in regain and disappointment in the long term. A safer approach is to establish an eating pattern that fits the person’s culture, budget, health status, and daily life. The goal of regular movement is not only to burn calories, but also to preserve muscle mass, support insulin sensitivity, improve sleep, and enhance mood. For that reason, treatment success should be measured not only by the scale, but also by overall health indicators. [2][3][4]
The goal of treatment is not only to lose weight quickly, but to build a system that can maintain the lost weight. For that reason, regular follow-up appointments and behavioral support are important. [2][3]
Reducing stigmatizing language in weight management may also increase willingness to seek treatment. One of the most important barriers that makes it harder for people to ask for help is shame. [1][2]
Specialist assessment is required for an individualized diagnostic and treatment plan.
FAQ
Is obesity caused only by eating too much?
No. Although nutrition is important, many factors play a role together, including genetics, environment, sleep, medications, psychosocial factors, and physical activity. [1][2][3]
Is BMI enough to define obesity?
BMI is a useful starting measure, but it is not sufficient on its own; waist circumference and associated health risks should also be assessed. [1][2]
Does even a small amount of weight loss help?
Yes. In some people, reducing about 5% to 10% of initial body weight may produce meaningful improvements in health risks. [3][4]
When are medication or surgery considered in obesity treatment?
If risk remains high despite lifestyle interventions, medication or surgical options may be considered according to BMI and coexisting diseases. [3]
Is obesity a character problem?
No. Obesity is a chronic and multifactorial disease, and a stigmatizing approach harms treatment. [1][2]
References
- 1.WHO. *Obesity and overweight*. 2025. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
- 2.MedlinePlus. *Obesity*. 2025. https://medlineplus.gov/obesity.html
- 3.NIDDK. *Treatment for Overweight & Obesity*. 2025. https://www.niddk.nih.gov/health-information/weight-management/adult-overweight-obesity/treatment
- 4.MedlinePlus Medical Encyclopedia. *Health risks of obesity*. 2025. https://medlineplus.gov/ency/patientinstructions/000348.htm
