The prevalence of obesity, measured by body mass index, has risen to an unacceptable levels in both men and women worldwide with resultant hazardous health implications. Genetic, environmental, and behavioural factors influence the development of obesity, and both the general public and health professionals stigmatize those who suffer from the disease. Obesity is associated with and contributes to a shortened lifespan, type 2 diabetes mellitus, cardiovascular disease, some cancers, kidney disease, obstructive sleep apnea, gout, osteoarthritis, and hepatobiliary disease, among others. Weight loss reduces all of these diseases in a dose-related manner—the more weight loss, the better the outcome. The phenotype of “medically healthy obesity” appears to be a transient state that progresses over time to an unhealthy phenotype, especially in children and adolescents. Programs that are effective for weight loss include peer-reviewed and approved lifestyle modification programs, diets, exercise programs, medications, and bariatric & metabolic surgery.
Obesity can be associated with several endocrine alterations arising as a result of changes in the hypothalamic-pituitary hormones axes. These include hypothyroidism, Cushing’s disease, hypogonadism and growth hormone deficiency. Further, obesity is also a common feature of the polycystic ovarian syndrome with hyperinsulinemia causing infertility in females.
Different phenotypes of obesity may have variable health implications. Abdominal obesity is considered to be a more hazardous condition than gluteofemoral, or gynecoid, obesity. In those with abdominal obesity, accumulation of intraperitoneal fat in the omentum and around viscera carries greater health risk than subcutaneous abdominal obesity.
Diets with many different macronutrient compositions can result in short-term weight loss. However, weight loss reaches a plateau within the first 3 to 6 months. After that, weight is regained and often returns to baseline by 1 to 2 years. Maintenance of long-term weight loss is strongly influenced by the ability to adhere to the dietary program. Behavioural support can significantly improve outcomes. There are variations among individuals in the response to each diet, which are larger than the difference in mean weight loss between comparison diets.