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**1. Classification and Measurement of Obesity:**
– Obesity is classified based on body mass index (BMI)
– WHO defines overweight as BMI 25 or higher, and obese as BMI 30 or higher
– CDC subdivides obesity into class 1, 2, and 3 based on BMI
– For children, obesity measures consider age, height, and weight
– Some countries redefine obesity based on their populations’ health risks

**2. Health Effects and Mortality Risk of Obesity:**
– Obesity increases the risk of metabolic diseases, cardiovascular disease, and cancer
– Associated with 2-20 years shorter life expectancy
– High BMI is a risk marker for diseases related to diet and physical activity
– Obesity is linked to osteoarthritis, Alzheimer’s, depression, and shorter life
– Mortality risk is lowest at specific BMI ranges for non-smokers and smokers

**3. Causes and Global Statistics of Obesity:**
– Obesity has individual, socioeconomic, and environmental causes
– Known causes include diet, physical activity, genetics, and mental disorders
– Economic policies, medications, and endocrine disorders also contribute
– In 2022, over 1 billion people worldwide were obese
– Obesity rates have doubled in adults and quadrupled in children since 1990

**4. Morbidity and Survival Paradox of Obesity:**
– Obesity increases the risk of physical and mental conditions
– Comorbidities include diabetes, high blood pressure, high cholesterol
– Obese individuals at higher risk for long COVID and severe COVID-19
– Some subgroups show improved health outcomes at higher BMI (obesity survival paradox)
– More aggressive treatment for obese individuals post-cardiac events may explain improved survival

**5. Factors Contributing to Obesity:**
– Excessive food intake and lack of physical activity major contributors to obesity
– Societal factors like accessible diets, reliance on cars, mechanized manufacturing also play a role
– Genetics play a role in obesity, with certain genes predisposing individuals
– Social determinants like economic inequality and access to healthy food influence obesity rates
– Environmental factors like urbanization and lack of public spaces for physical activity contribute to rising obesity rates

Obesity (Wikipedia)

Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classified as obese when their body mass index (BMI)—a person's weight divided by the square of the person's height—is over 30 kg/m2; the range 25–30 kg/m2 is defined as overweight. Some East Asian countries use lower values to calculate obesity. Obesity is a major cause of disability and is correlated with various diseases and conditions, particularly cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, certain types of cancer, and osteoarthritis.

Three silhouettes depicting the outlines of an optimally sized (left), overweight (middle), and obese person (right).
Silhouettes and waist circumferences representing optimal, overweight, and obese
SymptomsIncreased fat
ComplicationsCardiovascular diseases, type 2 diabetes, obstructive sleep apnea, certain types of cancer, osteoarthritis, depression
CausesExcessive consumption of energy-dense foods, sedentary work and lifestyles and lack of physical activity, changes in modes of transportation, urbanization, lack of supportive policies, lack of access to a healthy diet, genetics
Diagnostic methodBMI > 30 kg/m2
PreventionSocietal changes, changes in the food industry, access to a healthy lifestyle, personal choices
TreatmentDiet, exercise, medications, surgery
PrognosisReduced life expectancy
FrequencyOver 1 billion / 12.5% (2022)
Deaths2.8 million people per year

Obesity has individual, socioeconomic, and environmental causes. Some known causes are diet, physical activity, automation, urbanization, genetic susceptibility, medications, mental disorders, economic policies, endocrine disorders, and exposure to endocrine-disrupting chemicals.

While a majority of obese individuals at any given time attempt to lose weight and are often successful, maintaining weight loss long-term is rare. There is no effective, well-defined, evidence-based intervention for preventing obesity. Obesity prevention requires a complex approach, including interventions at societal, community, family, and individual levels. Changes to diet as well as exercising are the main treatments recommended by health professionals. Diet quality can be improved by reducing the consumption of energy-dense foods, such as those high in fat or sugars, and by increasing the intake of dietary fiber, if these dietary choices are available, affordable, and accessible. Medications can be used, along with a suitable diet, to reduce appetite or decrease fat absorption. If diet, exercise, and medication are not effective, a gastric balloon or surgery may be performed to reduce stomach volume or length of the intestines, leading to feeling full earlier, or a reduced ability to absorb nutrients from food.

Obesity is a leading preventable cause of death worldwide, with increasing rates in adults and children. In 2022, over 1 billion people were obese worldwide (879 million adults and 159 million children), representing more than a double of adult cases (and four times higher than cases among children) registered in 1990. Obesity is more common in women than in men. Today, obesity is stigmatized in most of the world. Conversely, some cultures, past and present, have a favorable view of obesity, seeing it as a symbol of wealth and fertility. The World Health Organization, the US, Canada, Japan, Portugal, Germany, the European Parliament and medical societies, e.g. the American Medical Association, classify obesity as a disease. Others, such as the UK, do not.

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