Weight training aims to build muscle by prompting two different types of hypertrophy: sarcoplasmic and myofibrillar. Sarcoplasmic hypertrophy leads to larger muscles and so is favored by bodybuilders more than myofibrillar hypertrophy, which builds athletic strength. Sarcoplasmic hypertrophy is triggered by increasing repetitions, whereas myofibrillar hypertrophy is triggered by lifting heavier weight. In either case, there is an increase in both size and strength of the muscles (compared to what happens if that same individual does not lift weights at all), however, the emphasis is different.
Some bodybuilders use drugs such as anabolic steroids and precursor substances such as prohormones to increase muscle hypertrophy. Anabolic steroids cause hypertrophy of both types (I and II) of muscle fibers, likely caused by an increased synthesis of muscle proteins. They also provoke undesired side effects including hepatotoxicity, gynecomastia, acne, the early onset of male pattern baldness and a decline in the body's own testosterone production, which can cause testicular atrophy. Other performance-enhancing substances used by competitive bodybuilders include human growth hormone (HGH), which can cause acromegaly.
Intentional weight loss is the loss of total body mass as a result of efforts to improve fitness and health, or to change appearance through slimming. Weight loss in individuals who are overweight or obese can reduce health risks, increase fitness, and may delay the onset of diabetes. It could reduce pain and increase movement in people with osteoarthritis of the knee. Weight loss can lead to a reduction in hypertension (high blood pressure), however whether this reduces hypertension-related harm is unclear.[not in citation given]
Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or even a combination of these. It is generally regarded as a medical problem when at least 10% of a person's body weight has been lost in six months or 5% in the last month. Another criterion used for assessing weight that is too low is the body mass index (BMI). However, even lesser amounts of weight loss can be a cause for serious concern in a frail elderly person.
Continuing weight loss may deteriorate into wasting, a vaguely defined condition called cachexia. Cachexia differs from starvation in part because it involves a systemic inflammatory response. It is associated with poorer outcomes. In the advanced stages of progressive disease, metabolism can change so that they lose weight even when they are getting what is normally regarded as adequate nutrition and the body cannot compensate. This leads to a condition called anorexia cachexia syndrome (ACS) and additional nutrition or supplementation is unlikely to help. Symptoms of weight loss from ACS include severe weight loss from muscle rather than body fat, loss of appetite and feeling full after eating small amounts, nausea, anemia, weakness and fatigue.
1 Reference for 5%: Blackburn G. (1995). Effect of degree of weight loss on health benefits. Obesity Research 3: 211S-216S. Reference for 10%: NIH, NHLBI Obesity Education Initiative. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. Available online: http://www.nhlbi.nih.gov/guidelines/obesity/ob_gdlns.pdf Cdc-pdf[PDF-1.25MB]External
In the first decade of the 21st century, the conceptualization of health as an ability opened the door for self-assessments to become the main indicators to judge the performance of efforts aimed at improving human health. It also created the opportunity for every person to feel healthy, even in the presence of multiple chronic diseases, or a terminal condition, and for the re-examination of determinants of health, away from the traditional approach that focuses on the reduction of the prevalence of diseases.