Obesity

Definition of Obesity: Obesity is a chronic disease characterized by excess body fat that impairs health. Health organizations define it based on body mass index (BMI), where BMI = weight (kg)/height (m)². For adults, overweight is BMI ≥ 25 and obesity is BMI ≥ 30who.intwho.int. (Children and teens use age-adjusted BMI charts.) In simple terms, obesity means having “abnormal or excessive fat accumulation”who.int. This excess fat increases the risk of many health problems (discussed below).

Prevalence – Global and in India: Obesity has risen sharply worldwide. According to the WHO, adult obesity has more than doubled since 1990, and adolescent obesity has quadrupledwho.int. In 2022 about 43% of adults globally were overweight and 16% were obesewho.int. That means roughly 1 in 8 people worldwide now has obesitywho.intwho.int. Rates vary by region; for example, only ~10–20% of adults in South-East Asia had obesity (2022), versus over 30% in the Americaswho.int. Childhood obesity is also rising: 35 million children under age 5 were overweight in 2024, and 160 million teenagers (5–19) had obesitywho.int.

In India, obesity is also climbing. A systematic review estimated “more than 135 million” Indians were overweight or obese (as of 2015)pubmed.ncbi.nlm.nih.gov. National surveys (NFHS-5, 2019–21) found roughly 23–24% of women (ages 15–49) and about 22% of men were overweight (BMI ≥25)researchgate.netpubmed.ncbi.nlm.nih.gov. (These figures combine overweight and obesity.) In NFHS-5, states like Punjab, Kerala and Delhi had the highest rates (around 30–40%)pubmed.ncbi.nlm.nih.gov. Earlier surveys showed obesity (BMI ≥30) was lower (often in the teens) but is rising, especially in urban areaspubmed.ncbi.nlm.nih.gov. In short, about one-quarter of Indian adults (15–49) now carry excess weight, and that proportion is growing every yearpubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.gov.

Common Causes and Risk Factors: Obesity results from a complex interplay of factors. Fundamentally, it occurs when calorie intake chronically exceeds energy expenditurenhlbi.nih.gov. But many genetic, behavioral and environmental factors influence this balance:

• Genetic predisposition: Obesity often runs in families. People inherit tendencies (genes) that affect appetite, metabolism and fat storage. Rare single-gene disorders (like Prader-Willi) directly cause severe obesity, but more commonly many gene variants each give a small risk. (Having obese parents greatly increases one’s risk.)cdc.gov

• Dietary habits: Eating high-calorie, nutrient-poor foods is a major driver. Diets rich in processed foods, sugary drinks, high fat or large portions add excess calories. Regular consumption of fast food, soft drinks, and snacks with added sugars or unhealthy fats is strongly linked to weight gaincdc.gov.

• Physical inactivity: Modern lifestyles are very sedentary. Jobs and leisure often involve sitting (computer, TV, commuting), and daily routines may lack exercise. Physical inactivity is a key risk factor: most adults need at least 150 minutes of moderate exercise per week, but many fall shortcdc.govwho.int.

• Sleep patterns: Chronic sleep deprivation or poor-quality sleep can alter hormones that regulate hunger and satiety, leading to overeating. Insufficient sleep is recognized as a risk factor for weight gaincdc.gov.

• Stress and emotional factors: Long-term stress or emotional issues can trigger overeating (especially of comfort foods) and hormonal changes (e.g. high cortisol) that promote fat storagecdc.gov. Mental health problems (depression, anxiety) can also disrupt diet and activity.

• Medications and medical conditions: Certain health conditions (hypothyroidism, polycystic ovary syndrome, Cushing’s syndrome) can cause weight gain. Some medications (antidepressants, antipsychotics, steroids, insulin, etc.) also raise obesity risk by altering metabolism or appetitecdc.gov.

• Socioeconomic and environmental factors: Low income or living in a “food desert” can limit access to healthy foods and safe exercise spaces. Built environments without sidewalks or parks discourage activity. Marketing and availability of unhealthy foods (high in sugar/fat) influence choices. In sum, an “obesogenic environment” – one that encourages excess calorie intake and discourages activity – greatly raises obesity riskcdc.gov.

All these factors often combine. For example, a person with a genetic predisposition living in a fast-food–rich environment who leads a sedentary lifestyle faces especially high risk. Importantly, most causes of obesity are at least partly modifiable: diet, exercise and lifestyle habits can be changed to reduce risk.

Health Consequences: Obesity affects nearly every organ and system in the body. Physically, it greatly raises the risk of chronic diseases and mortality. Well-known consequences include type 2 diabetes (insulin resistance), heart disease and stroke (through high blood pressure, cholesterol and inflammation), sleep apnea, fatty liver disease, osteoarthritis (joint wear), and many cancers (e.g. breast, colon, uterine)who.int. In fact, WHO notes obesity is a major contributor to non-communicable disease globally, often shortening lifespan. Carrying extra weight also causes mechanical issues: it strains bones/joints (leading to back pain, arthritis) and impairs mobility. In women, obesity raises infertility and pregnancy complication risks; in men, it is linked to lower testosterone and erectile dysfunction.

Obesity also impacts mental and social well-being. People with obesity have higher rates of depression, anxiety and low self-esteem, partly due to hormone effects and partly to psychosocial factorsncbi.nlm.nih.gov. Weight stigma and discrimination are pervasive: society often unfairly views those with obesity as lazy or undisciplined. This stigma can lead to bullying, social isolation, reduced employment opportunities and even bias in healthcarencbi.nlm.nih.gov. All this contributes to stress and lowered quality of life. For example, studies show individuals with obesity have significantly increased odds of developing clinical depression over timencoa.orgncbi.nlm.nih.gov. Body image dissatisfaction and disordered eating (bingeing or extreme dieting) are also common. In summary, the physical, psychological, and social burden of obesity is tremendous – it not only causes chronic illness, but also emotional distress and social challenges.

Diagnostic Criteria: The simplest diagnostic tool is BMI. By definition, an adult with BMI ≥30 is obesewho.int. Often, BMI is reported in categories (e.g. class I, II, III obesity), but for lay audiences we simply note the cutoff. BMI has limitations (it does not distinguish fat from muscle), so additional measures are sometimes used. Waist circumference is one such measure of abdominal fat. High waist circumference (above ~102 cm (40 in) in men or ~88 cm (35 in) in women) indicates central obesity and higher metabolic risk. (Some guidelines set lower waist cutoffs for Asian populations.) Clinicians may also look at waist-to-hip ratio or body fat percentage when available. In children, age- and sex-adjusted BMI percentiles are used. In all cases, these measures help assess how excess weight may be impacting health.

Maintaining a healthy weight involves choosing nutrient-rich foods. Eating plenty of fruits and vegetables (as pictured) and reducing high-fat, high-sugar foods helps create a calorie deficit needed for weight losswho.int. Combined with regular physical activity, dietary changes are the cornerstone of obesity management.

Management Strategies: Treating obesity usually requires a multifaceted approach. Lifestyle change is the foundation:

• Diet and nutrition: A cornerstone is a calorie-controlled, balanced diet. This means reducing intake of processed foods, sugary snacks/drinks, and high-fat meals while focusing on vegetables, fruits, whole grains, lean proteins and healthy fats. Portion control and mindful eating are key. Various diets (Mediterranean, low-carb, etc.) can work if they create an energy deficit. In practice, programs may use meal plans or meal replacements. Guidance from a dietitian is often helpful.

• Physical activity: Regular exercise boosts weight loss and maintains health. Guidelines recommend at least 150 minutes per week of moderate-intensity aerobic activity (brisk walking, cycling) for adultswho.int (or 75 minutes of vigorous activity). Strength training (2–3 times weekly) helps build muscle, which increases metabolism. Even everyday activities (walking, taking stairs, gardening) are encouraged. For obese individuals, exercise programs often start slowly and increase over time.

• Behavioral therapy: Counseling and support are vital. This can include cognitive-behavioral therapy techniques: self-monitoring (keeping food/activity logs), goal-setting, problem-solving, and stimulus control (e.g. removing temptations at home). Many find success in structured programs (like the Diabetes Prevention Program) or support groups. Psychological support also addresses emotional eating and motivation.

After these lifestyle steps, additional treatments may be needed:

• Medications: Several FDA-approved medications can aid weight loss, especially when lifestyle changes alone are insufficient. For example, orlistat (Xenical) blocks fat absorption; it is approved for BMI ≥30 (or ≥27 with other conditions)pmc.ncbi.nlm.nih.gov. More recently, new drugs like GLP-1 agonists (liraglutide, semaglutide) and the dual GIP/GLP-1 agonist tirzepatide have shown major effects. In clinical trials, these drugs produced average weight losses of 10–15% or more. For instance, the STEP trial reported a mean ~15% weight reduction on semaglutide (2.4 mg weekly) over 68 weeks, versus ~2% on placebopmc.ncbi.nlm.nih.gov. Tirzepatide (at higher doses) achieved ~20–22% weight loss in trialspmc.ncbi.nlm.nih.gov. (Patients typically use these under doctor supervision and combine them with lifestyle therapy.) Other medications include bupropion/naltrexone and phentermine/topiramate, which give more modest losses (~5–10%). All medications have potential side effects and are usually indicated for BMI ≥30 (or ≥27 with health risks).

• Bariatric (Weight-Loss) Surgery: For severe obesity, surgical options may be considered. Procedures like gastric bypass or sleeve gastrectomy restrict stomach size and/or reduce nutrient absorption. Surgery is typically recommended if BMI ≥40, or ≥35 with serious obesity-related conditions (diabetes, heart disease, etc.)pmc.ncbi.nlm.nih.gov. (Recent guidelines suggest even lower BMI cutoffs for certain populations.) Bariatric surgery can produce substantial weight loss (often 25–35% of initial body weight) and can markedly improve or resolve comorbidities like diabetes. However, it carries risks and requires lifelong medical follow-up, including nutritional monitoring.

In all cases, treatment is personalized. A healthcare team (physician, dietitian, psychologist, etc.) typically guides the approach. Success usually involves long-term lifestyle change; studies show that maintenance of weight loss often requires ongoing support and monitoring.

Prevention and Public Health Initiatives: Preventing obesity is as important as treating it. At the individual level, the same lifestyle principles apply early: healthy eating and regular activity should start in childhood. For infants, exclusive breastfeeding for the first 6 months is recommended and has been linked to lower obesity risk later onwho.int. Children should be encouraged to play, limit screen time, and eat a balanced diet. Families and schools can educate about nutrition (e.g. reading food labels) and make healthy food available.

At the community and policy level, governments and organizations implement initiatives to promote a healthy weight environment. Examples include:

• Nutrition and food policies: Subsidizing fruits and vegetables, taxing sugar-sweetened beverages, and regulating food labeling and advertising help shift diets toward healthier options. School nutrition standards (serving more whole grains, fruits, vegetables and limiting junk food) are widely used. The WHO and various countries issue dietary guidelines (e.g. “eat at least 5 servings of fruits/veggies per day”who.int) and run public awareness campaigns about healthy eating.

• Physical activity promotion: Urban planning can create more parks, walking/bike paths and safe recreational spacescdc.govcdc.gov. Many communities organize events like “Walk to School” days and build sports facilities. Guidelines encourage schools to incorporate daily physical education and active breaks. Workplaces are also targeted with programs (on-site gyms, activity breaks). Experts note that making active living easier (for example, safe sidewalks and bike lanescdc.gov) is crucial for prevention.

• Education and healthcare initiatives: Public health campaigns (media spots, school programs) raise awareness that obesity is a disease and encourage healthy habits. Healthcare providers play a role by counseling patients about weight, using non-stigmatizing language and discussing BMI and health risks in a sensitive waycdc.gov. Pregnancy and early childhood programs (like WIC in the US) offer nutrition support to reduce obesity risk from the start of life.

These efforts work best when combined. For example, the U.S. “Nutrition and Physical Activity Initiative” aims to end hunger and reduce diet-related disease by improving school meals, promoting breastfeeding, and funding community fitness programscdc.gov. Internationally, WHO’s “Global Strategy on Diet, Physical Activity and Health” encourages countries to enact policies that make healthy choices the easy choices.

Key Takeaways: Obesity is defined by excess fat (often BMI ≥30) and is highly prevalent worldwide. It arises from genes interacting with lifestyle factors: high-calorie diets, low activity, sleep and stress. The health consequences are severe – from heart disease and diabetes to depression and social stigmawho.intncbi.nlm.nih.gov. Diagnosis is usually by BMI (and sometimes waist measurements)who.intwho.int. Treatment must be comprehensive: dietary change, exercise, behavior therapy, and when needed, medications or surgery. Prevention requires both personal habits and public health measures: educating people about nutrition and exercise, ensuring access to healthy foods, and creating environments that support active livingcdc.govcdc.gov. By understanding these facets of obesity and addressing them systematically, healthcare providers and communities can work together to curb this growing epidemic.

Sources: Authoritative health organizations and recent studies were used. For example, WHO fact sheets and CDC guidelines provide definitions, statistics and prevention tipswho.intwho.intwho.int. Peer-reviewed research and reviews document risk factors and treatment outcomespubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov.