The fact of losing weight or of becoming thinner.
Weight loss occurs when energy expenditure exceeds energy intake. Many factors can affect either energy intake or energy expenditure and lead to loss of body weight. A comprehensive review of factors involved in weight loss is beyond the scope of this book; however, some general principals, particularly related to athletes, will be provided.
A measurable decline in body weight (BW) either intentionally, or as a result of malnutrition or illness. It is considered mild when 5% of BW is lost, moderate when 5-10% of BW is lost, and high when more than 10% of BW is lost.
Whenever there is a reduction in energy intake compared to energy expenditure, weight loss is probable. This reduction can arise from intentional weight management efforts or modifications in diet and physical activity. Weight loss can also occur due to fluid loss, such as sweating in a hot environment, or it might manifest as a symptom of an underlying medical condition. In cases of unexplained weight loss, it is essential to seek medical evaluation and guidance from a doctor.
Numerous illnesses can disrupt an individual’s appetite to the extent that they lose the inclination to eat, leading to subsequent weight loss. A diminished appetite can also serve as an indicator of overall poor health. Conditions such as depression can reduce a person’s motivation to eat, peptic ulcers may induce pain and, in some instances, food avoidance, while certain kidney disorders can result in a loss of appetite due to uraemia’s effects (elevated levels of the waste product urea in the bloodstream). In cases of anorexia nervosa and bulimia, intricate psychological factors play a role in an individual’s eating patterns, often yielding dramatic consequences.
Digestive disorders like gastroenteritis can result in weight loss due to symptoms such as vomiting or diarrhea. Weight can also be influenced by conditions like esophageal cancer and stomach cancer. Furthermore, the malabsorption of nutrients in specific intestinal or pancreatic disorders can have an impact on an individual’s weight.
Certain medical conditions induce weight loss by accelerating the metabolic activity within cells. Examples of such conditions include various forms of cancer, chronic infections like tuberculosis, and hyperthyroidism, which is characterized by an overactive thyroid gland. Untreated diabetes mellitus can also lead to weight loss.