Weight loss, in the context of medicine, health, or physical fitness, is a reduction of the total body mass, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon, and other connective tissue. It can occur unintentionally due to an underlying disease or can arise from a conscious effort to improve an actual or perceived overweight or obese state.
Unintentional[edit]
Characteristics[edit]
Unintentional weight loss may be a result of loss of fat, muscle atrophy, fluid loss or a combination of these.[1][2] It is generally regarded as a medical problem when at least 10% of an elderly person's body weight has been lost in six months[1] or 5% in the last month.[3] Another criterion used for assessing weight that is too low is the body mass index(BMI).[4] However, even lesser amounts of weight loss can be a cause for serious concern in a frail elderly person.[5]
Unintentional weight loss can occur because of an inadequately nutritious diet relative to a person's energy needs (generally called malnutrition). Disease processes, changes in metabolism, hormonal changes, medications or other treatments, disease- or treatment-related dietary changes, or reduced appetite associated with a disease or treatment can also cause unintentional weight loss.[1][2][6][7][8]
Continuing weight loss may deteriorate into wasting, a vaguely defined condition called cachexia.[5] Cachexia differs from starvation in part because it involves a systemic inflammatory response.[5] It is associated with poorer outcomes.[1][5][6] 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.[9] 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.[9]
Serious weight loss may reduce quality of life, impair treatment effectiveness or recovery, worsen disease processes and be a risk factor for earlier mortality.[1][5] Malnutrition can affect every function of the human body, from the cells to the most complex functions, including:[4]
- immune response;
- wound healing;
- muscle strength (including respiratory muscles);
- renal capacity and depletion leading to water and electrolyte disturbances;
- thermoregulation; and
- menstruation.
In addition, malnutrition can lead to vitamin and other deficiencies and to inactivity, which in turn may pre-dispose to other problems, such as pressure sores.[4]
Unintentional weight loss can be the characteristic leading to diagnosis of diseases such as cancer[1] and type 1 diabetes.[10]
In the UK, up to 5% of the general population is underweight, but more than 10% of those with lung or gastrointestinal diseases and who have recently had surgery.[4] According to data in the UK using the Malnutrition Universal Screening Tool ('MUST'), which incorporates unintentional weight loss, more than 10% of the population over the age of 65 is at risk of malnutrition.[4] A high proportion (10-60%) of hospital patients are also at risk, along with a similar proportion in care homes.[4]
Causes[edit]
[edit]
Disease-related malnutrition can be considered in four categories:[4]
| Problem | Cause |
|---|---|
| Impaired intake | Poor appetite can be a direct symptom of an illness, or an illness could make eating painful or induce nausea. Illness can also cause food aversion.
Inability to eat can result from: diminished consciousness or confusion, or physical problems affecting the arm or hands, swallowing or chewing. Eating restrictions may also be imposed as part of treatment or investigations. Lack of food can result from: poverty, difficulty in shopping or cooking, and poor quality meals.
|
| Impaired digestion &/or absorption | This can result from conditions that affect the digestive system. |
| Altered requirements | Changes to metabolic demands can be caused by illness, surgery and organ dysfunction. |
| Excess nutrient losses | Losses from the gastrointestinal can occur because of symptoms such as vomiting or diarrhea, as well as fistulae and stomas. There can also be losses from drains, including nasogastric tubes.
Other losses: Conditions such as burns can be associated with losses such as skin exudates.
|
Weight loss issues related to specific diseases include:
- As chronic obstructive pulmonary disease (COPD) advances, about 35% of patients experience severe weight loss called pulmonary cachexia, including diminished muscle mass.[6] Around 25% experience moderate to severe weight loss, and most others have some weight loss.[6] Greater weight loss is associated with poorer prognosis.[6]Theories about contributing factors include appetite loss related to reduced activity, additional energy required for breathing, and the difficulty of eating with dyspnea (labored breathing).[6]
- Cancer, a very common and sometimes fatal cause of unexplained (idiopathic) weight loss. About one-third of unintentional weight loss cases are secondary to malignancy. Cancers to suspect in patients with unexplained weight loss include gastrointestinal, prostate, hepatobillary (hepatocellular carcinoma, pancreatic cancer), ovarian, hematologic or lung malignancies.
- People with HIV often experience weight loss, and it is associated with poorer outcomes.[11] Wasting syndrome is an AIDS-defining condition.[11]
- Gastrointestinal disorders are another common cause of unexplained weight loss – in fact they are the most common non-cancerous cause of idiopathic weight loss.[citation needed] Possible gastrointestinal etiologies of unexplained weight loss include: celiac disease, peptic ulcer disease, inflammatory bowel disease (crohn's diseaseand ulcerative colitis), pancreatitis, gastritis, diarrhea and many other GI conditions.
- Infection. Some infectious diseases can cause weight loss. Fungal illnesses, endocarditis, many parasitic diseases, AIDS, and some other subacute or occult infections may cause weight loss.
- Renal disease. Patients who have uremia often have poor or absent appetite, vomiting and nausea. This can cause weight loss.
- Cardiac disease. Cardiovascular disease, especially congestive heart failure, may cause unexplained weight loss.
- Connective tissue disease
- Neurologic disease, including dementia[12]
- Stress can cause weight loss[citation needed]. However, recent research (Jastebott, Potenza et al. 2010) shows a correlation between obesity and high levels of stress.[13]
- Oral, taste or dental problems (including infections) can reduce nutrient intake leading to weight loss.[9]
[edit]
Medical treatment can directly or indirectly cause weight loss, impairing treatment effectiveness and recovery that can lead to further weight loss in a vicious cycle.[1]
Many patients will be in pain and have a loss of appetite after surgery.[1] Part of the body's response to surgery is to direct energy to wound healing, which increases the body's overall energy requirements.[1] Surgery affects nutritional status indirectly, particularly during the recovery period, as it can interfere with wound healing and other aspects of recovery.[1][4] Surgery directly affects nutritional status if a procedure permanently alters the digestive system.[1] Enteral nutrition (tube feeding) is often needed.[1] However a policy of 'nil by mouth' for all gastrointestinal surgery has not been shown to benefit, with some suggestion it might hinder recovery.[14]
Early post-operative nutrition is a part of Enhanced Recovery After Surgery protocols.[15] These protocols also include carbohydrate loading in the 24 hours before surgery, but earlier nutritional interventions have not been shown to have a significant impact.[15]
Social conditions[edit]
Social conditions such as poverty, social isolation and inability to get or prepare preferred foods can cause unintentional weight loss, and this may be particularly common in older people.[17] Nutrient intake can also be affected by culture, family and belief systems.[9] Ill-fitting dentures and other dental or oral health problems can also affect adequacy of nutrition.[9]
Loss of hope, status or social contact and spiritual distress can cause depression, which may be associated with reduced nutrition, as can fatigue.[9]
Intentional[edit]
Intentional weight loss refers to the loss of total body mass as a result of efforts to improve fitness and health, and/or to change appearance.
Weight loss in individuals who are overweight or obese can reduce health risks,[18] increase fitness,[19] and may delay the onset of diabetes.[18] It could reduce pain and increase movement in people with osteoarthritis of the knee.[19] Weight loss can lead to a reduction in hypertension (high blood pressure), however whether this reduces hypertension-related harm is unclear.[18]
Weight loss occurs when an individual is in a state of negative thermodynamic flux: when the body is expending more energy (i.e. in work and metabolism) than it is consuming (i.e., from food or other nutritional supplements), it will use stored reserves from fat or muscle, gradually leading to weight loss.
It is not uncommon for some people who are at their ideal body weight to seek additional weight loss in order to improve athletic performance or meet required weight classification for participation in a sport. Others may be driven to lose weight to achieve a more attractive appearance. Being underweight is associated with health risks such as difficulty fighting off infection, osteoporosis, decreased muscle strength, trouble regulating body temperature and even increased risk of death.[20]
According to the U.S. Food and Drug Administration (FDA), healthy individuals seeking to maintain their weight should consume 2,000 calories per day.[21]
According to the Dietary Guidelines for Americans those who achieve and manage a healthy weight do so most successfully by being careful to consume just enough calories to meet their needs, and being physically active.[22]
Low-calorie regimen diets are also referred to as balanced percentage diets. Due to their minimal detrimental effects, these types of diets are most commonly recommended by nutritionists. In addition to restricting calorie intake, a balanced diet also regulates macronutrient consumption. From the total number of allotted daily calories, it is recommended that 55% should come from carbohydrates, 15% from protein, and 30% from fats with no more than 10% of total fat coming from saturated forms.[23] For instance, a recommended 1,200 calorie diet would supply about 660 calories from carbohydrates, 180 from protein, and 360 from fat. Some studies suggest that increased consumption of protein can help ease hunger pangs associated with reduced caloric intake by increasing the feeling of satiety.[24] Calorie restriction in this way has many long-term benefits. After reaching the desired body weight, the calories consumed per day may be increased gradually, without exceeding 2,000 net (i.e. derived by subtracting calories burned by physical activity from calories consumed). Combined with increased physical activity, long-term low-calorie diets are thought to be most effective long term, unlike crash diets which can achieve short term results, at best. Physical activity could greatly enhance the efficiency of a diet. The healthiest weight loss regimen, therefore, is one that consists of a balanced diet and moderate physical activity.[citation needed]
Weight gain has been associated with excessive consumption of fats, sugars, carbohydrates in general, and alcohol.[citation needed] Depression, stress or boredom may also contribute to weight increase,[citation needed] and in these cases, individuals are advised to seek medical help. A 2010 study found that dieters who got a full night's sleep lost more than twice as much fat as sleep-deprived dieters.[25][26]
The majority of dieters regain weight over the long term.[27]
There is some research that suggests that all calories are not created equal (in other words, a calorie is not necessarily a calorie). Thus the human body might not gain the same amount of weight from 500 calories of certain foods than it would from 500 calories of other foods.[28][29]
Therapeutic weight loss techniques[edit]
The least intrusive weight loss methods, and those most often recommended, are adjustments to eating patterns and increased physical activity, generally in the form of exercise. The World Health Organization recommended that people combine a reduction of processed foods high in saturated fats, sugar and salt[30] and caloric content of the diet with an increase in physical activity.[31]
An increase in fiber intake is also recommended for regulating bowel movements.
Other methods of weight loss include use of drugs and supplements that decrease appetite, block fat absorption, or reduce stomach volume.
Bariatric surgery may be indicated in cases of severe obesity. Two common bariatric surgical procedures are gastric bypass and gastric banding.[32] Both can be effective at limiting the intake of food energy by reducing the size of the stomach, but as with any surgical procedure both come with their own risks[33] that should be considered in consultation with a physician.
Dietary supplements, though widely used, are not considered a healthy option for weight loss.[34] Even though a many are available, very few are effective long term.[35]
Virtual gastric band uses hypnosis to make the brain think the stomach is smaller than it really is and hence lower the amount of food ingested. This brings as a consequence weight reduction. This method is complemented with psychological treatment for anxiety management and with hypnopedia. Research has been conducted into the use of hypnosis as a weight management alternative.[36][37][38][39] In 1996 a study found that cognitive-behavioral therapy (CBT) was more effective for weight reduction if reinforced with hypnosis.[37]Acceptance and Commitment Therapy ACT, a mindfulness approach to weight loss, has also in the last few years been demonstrating its usefulness.[40]
Crash dieting[edit]
A crash diet refers to willful nutritional restriction (except water) for more than 12 waking hours. The desired result is to have the body burn fat for energy with the goal of losing a significant amount of weight in a short time. Crash dieting can be dangerous to health and this method of weight loss is not recommended by physicians.[41]
According to the Academy of Nutrition and Dietetics,[42] "If the diet or product sounds too good to be true, it probably is. There are no foods or pills that magically burn fat. No super foods will alter your genetic code. No products will miraculously melt fat while you watch TV or sleep." Certain ingredients in supplements and herbal products[vague] can be dangerous and even deadly for some people.[citation needed]