Underweight
Underweight | |
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The underweight range according to the body mass index (BMI) is the white area on the chart. | |
Specialty | Endocrinology |
Part of a series on |
Human body weight |
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An underweight person is a person whose
Assessment
Category[1] | BMI (kgm−2) |
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Underweight (severe) | < 16.0 |
Underweight (moderate) | 16.0 – 16.9 |
Underweight (mild) | 17.0 – 18.4 |
Normal weight | 18.5 – 24.9 |
Overweight | 25.0 – 29.9 |
Obese | ≥ 30.0 |
The body mass index, a ratio of a person's weight to their height, has traditionally been used to assess the health of a person as it pertains to weight: under the cut-off point at a BMI of 18.5, a person is considered underweight.[2] The calculation is either weight in kilograms divided by height in meters, squared, or weight in pounds times 703, divided by height in inches, squared. Another measure of underweight is through comparison to the average weight of a cohort of people of a similar age and height: people who are at least 15% to 20% below the average weight for the group are considered underweight.[3]
Prevalence
Using the body mass index as a measure of weight-related health, with data from 2014, age-standardised global prevalence of underweight in women and men were 9.7% and 8.8%, respectively. These values were lower than what was reported for 1975 as 14.6% and 13.8%, respectively, indicating a worldwide reduction in the extent of undernutrition.[6]
Causes
A person may be underweight due to
Being underweight is associated with certain medical conditions, including
A common belief is that healthy underweight individuals can ‘eat what they want’ and then burn it off either by high levels of activity or elevated metabolism. It has been shown, however, that individuals with BMI < 18.5 eat about 12% less calories than individuals with normal BMI (21.5 to 25) and they are 23% less physically active (by accelerometry).[17] Underweight people tend to have low appetites and typically eat little, sporadically or infrequently.
Problems
Being underweight can be a symptom of an underlying condition, in which case it is secondary. Unexplained weight loss may require a professional medical diagnosis by a physician.[18]
Being underweight can also cause other conditions, in which case it is primary. Severely underweight individuals may have poor physical
In women, being severely underweight, as a result of an eating disorder or due to excessive strenuous exercise, can result in amenorrhea (absence of menstruation),[20] infertility or complications during pregnancy if gestational weight gain is too low.[citation needed]
Malnourishment can also cause anemia and hair loss.
Being underweight is an established[21] risk factor for osteoporosis, even for young people. This is seen in individuals suffering from relative energy deficiency in sport, formerly known as female athlete triad: when disordered eating or excessive exercise cause amenorrhea, hormone changes during ovulation leads to loss of bone mineral density.[22][23] After this low bone mineral density causes the first spontaneous fractures, the damage is often irreversible.
Although being underweight has been reported to increase mortality at rates comparable to that seen in morbidly obese people,[24] the effect is much less drastic when restricted to non-smokers with no history of disease,[25] suggesting that smoking and disease-related weight loss are the leading causes of the observed effect.
Treatment
Diet
Underweight individuals may be advised to gain weight by increasing
Exercise
Another way for underweight people to gain weight is by exercising, since muscle hypertrophy increases body mass. Weight lifting exercises are effective in helping to improve muscle tone as well as helping with weight gain.[30] Weight lifting has also been shown to improve bone mineral density,[31] which underweight people are more likely to lack.[32]
Exercise is
Appetite stimulants
Certain drugs may increase appetite either as their primary effect or as a side effect. Antidepressants, such as
See also
- Essential nutrient
- List of phytochemicals in food
- Body image
- Emaciation
- Malnutrition
- Stunted growth
References
- ^ The SuRF Report 2 (PDF). The Surveillance of Risk Factors Report Series (SuRF). World Health Organization. 2005. p. 22.
- ^ "Assessing Your Weight and Health Risk". National Heart, Lung and Blood Institute. Retrieved 23 September 2012.
- ^ Mahan, L. Kathleen (2000). Krause's Food, Nutrition & Diet Therapy, 10th Ed. Philadelphia: W.B. Saunders Co.
- PMID 26217501.
- ^ "ACE Fit - Body Fat Percentage Calculator". Retrieved 28 February 2020.
- PMID 27115820.
- ^ "Body Shape 'Is Down to Genes'". Indian Express. Retrieved October 23, 2010.
- ^ "'Skinny Gene' Exists". Science Daily. September 5, 2007. Retrieved October 23, 2010.
- ^ "What are Eating Disorders?". NIMH. Archived from the original on 23 May 2015. Retrieved 24 May 2015.
- PMID 19719398.
- ^ "Unexplained Weight Loss - Reasons, Symptoms & Causes". Retrieved 2017-11-28.
- ^ Milas, Kresimira. "Hyperthyroidism Symptoms - Signs and symptoms caused by excessive amounts of thyroid hormones". Endocrine Web. Retrieved 24 September 2012.
- ^ "Signs and Symptoms of Cancer". American Cancer Society. Retrieved 24 September 2012.
- PMID 10083790.
- PMID 24506978.
- PMID 15001063.
- S2CID 250576685.
- ^ "Weight loss - unintentional: MedlinePlus Medical Encyclopedia". medlineplus.gov. Retrieved 2022-11-18.
- S2CID 14509705
- ^ "MJH Life Sciences™ | Informing Healthcare Professionals •". 10 August 2022.
- PMID 18221845.
- PMID 8013041.
- PMID 8173855.
- PMID 6585126.
- ^ Body Weight and Mortality:What is the optimum weight for a longer life?.
- ^ Zeratsky, Katherine (23 August 2011). "Underweight? See how to add pounds healthfully". Nutrition and healthy eating. Mayo Clinic. Retrieved 19 March 2012.
- ^ "Gain Weight and Be Healthy". About.com. Retrieved October 23, 2010.
- ^ "Achieving Healthy Weight Gain". Health Central. Retrieved October 23, 2010.
- ^ "Healthy Weight Gain". Children's Hospital Boston, Center for Young Women's Health. Retrieved October 23, 2010.
- ^ "Men's Health". Men's Health. Retrieved October 23, 2010.
- S2CID 72034011.
- S2CID 1298271.
- S2CID 22837100.