Obesity occurs when an individual eats more calories than he/she burns. It is an individual clinical condition. However, research reveals that it is now becoming a serious public health problem increasing by the day. People affected by cardiovascular diseases, type 2 diabetes, and osteoarthritis are more prone to this condition. Obesity is evaluated in absolute terms by measuring BMI. Along with calculating the body mass index, obesity is also evaluated in terms of its distribution through the waist circumference. In addition, the presence of other medical conditions that could influence risk of complication also needs to be checked. BMI is calculated by dividing the patient's weight by the square of the height and expressing the answer in metric or customary units. The World Health Organization has specified that a BMI less than 18.5 is underweight, 18.5-24.9 is normal, 25.0-29.9 is overweight, and 30.0-39.9 is obese. Physicians consider race, ethnicity, and lean mass or muscularity, while checking for obesity. The person's age and sex also affects the interpretation of BMI. Mild obesity is not a risk factor for cardiac problems and hence it cannot be used as a sole epidemiological predictor of cardiovascular health. It is essential to know that BMI does not take into account differing ratios of adipose to lean tissue. It also does not distinguish between the different forms of adiposity. The absolute waist circumference or the waist to hip ratio is used to measure central obesity. Research reveals that the waist circumference explains obesity-related health risk better than BMI. Obesity can also be determined by assessing the body fat percent. Men with more than 25% body fat and women with more than 30% body fat are categorized as obese. The most accepted method to measure body fat precisely, so far, has been to weigh a person underwater, with special equipment. The other two simpler methods are the skinfold test and the bioelectrical impedance analysis. However, their routine use is discouraged. The risk factors and diseases that are commonly associated with obesity are also used to establish a clinical diagnosis of the condition. In fact, sleep apnea and coronary heart diseases are life-threatening conditions that indicate clinical treatment of obesity. Obesity increases the chances of mortality. In fact, a BMI of over 32 is associated with a doubled risk of death. This kind of BMI alters the body's response to insulin and increases the chances of prothrombotic state. Male-type or waist-predominant obesity is characterized by a high waist-hip ratio. It is an important risk factor for the clustering of a number of diseases and risk factors connected with cardiovascular disease. Most research reveals that the combination of excessive nutrient intake and sedentary lifestyle is the main cause for obesity in the Western society. Despite the widespread awareness, it is evident that overeating still remains a problem. An increasingly sedentary lifestyle also plays a role in the onset of obesity at an early stage. Certain lifestyle habits and under investigated lifestyle like insufficient sleep, intake of food substances that interfere with lipid metabolism, increased rates of smoking that invariably suppresses appetite, increased use of medication, and pregnancy at a later age also influence obesity. The caloric imbalance that results in obesity is the result of a number of related genetic and environmental factors. There are polymorphisms in various genes that control appetite and metabolism. Various genetic conditions that feature obesity have been identified. There are certain ethnic groups that are more prone to obesity than others. Individuals with greater adipose reserves are more likely to survive famine. Mental illnesses, like eating disorders, also increase obesity risk. The role of bacteria in the digestive tract in the development of obesity is also being investigated. Bacteria participate in digestion, and hence, alterations in the proportion of particular strains could explain the cause.