Obesity
Definition and Classification
Obesity is a complex, chronic, relapsing condition characterized by an excessive accumulation of body fat, or adipose tissue, to the extent that it may have an adverse effect on health. It is often defined by the Body Mass Index (BMI), a measure that compares a person's weight and height. However, it is important to note that BMI does not directly measure body fat, and there are other methods to assess body fat and distribution, such as skinfold thickness measurements, bioelectrical impedance, and dual-energy x-ray absorptiometry (DEXA).
Obesity can be further classified into three types: monogenic obesity, syndromic obesity, and the most common type, multifactorial obesity. Monogenic obesity is caused by changes or mutations in a single gene. Syndromic obesity is characterized by intellectual impairments and physical abnormalities in addition to obesity. Multifactorial obesity is associated with a combination of environmental factors, physical activity levels, and genetics.
Epidemiology
Obesity has become a global epidemic, with the World Health Organization (WHO) estimating that more than 1.9 billion adults were overweight in 2016, and of these, over 650 million were obese. The prevalence of obesity has nearly tripled since 1975. It is a major public health issue in both developed and developing countries, affecting all age groups and socioeconomic classes.
Etiology
The etiology of obesity is multifactorial, involving a complex interplay between genetic, behavioral, and environmental factors. Genetic factors include polymorphisms in various genes that control appetite and metabolism. Behavioral factors include dietary habits, physical activity levels, and patterns of sleep. Environmental factors include the food and built environments, and social and economic factors.
Pathophysiology
The pathophysiology of obesity is centered on the energy balance equation, which states that weight gain occurs when energy intake exceeds energy expenditure. At the molecular level, obesity is characterized by an increase in the size and number of adipocytes, or fat cells. This leads to an increase in adipose tissue mass and changes in the secretion of adipokines, which are bioactive molecules that play a role in appetite regulation, insulin sensitivity, and inflammation.
Clinical Manifestations
Obesity is associated with a wide range of health problems, including cardiovascular diseases, type 2 diabetes, certain types of cancer, and sleep apnea. It can also lead to psychosocial problems and a reduced quality of life. The risk of these health problems increases with the severity of obesity.
Diagnosis
The diagnosis of obesity is typically based on BMI. However, as mentioned earlier, BMI does not directly measure body fat. Therefore, additional tests may be used to assess body fat and distribution, as well as to screen for potential obesity-related complications.
Management
The management of obesity requires a multifaceted approach that includes dietary changes, increased physical activity, behavior modification, and sometimes medication or surgery. The goal of treatment is not just weight loss, but also the prevention of weight regain and improvement in obesity-related complications.
Prevention
Prevention strategies for obesity focus on maintaining an energy balance between calories consumed and calories expended. This can be achieved through a healthy diet and regular physical activity. It is also important to create supportive environments that make healthy lifestyle choices easier.