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96-416: Stretch marks , also known as striae ( / ˈ s t r aɪ iː / ) or striae distensae , are a form of scarring on the skin with an off-color hue. Over time, they may diminish, but will not disappear completely. Striae are caused by tearing of the dermis during periods of rapid growth of the body, such as during puberty or pregnancy , in which they usually form during the last trimester . Usually on
192-514: A silk -derived sericin hydrogel dressing was undergoing research, the material was shown to prevent scar formation. By 2021, more people were paying attention to the possibility of scar revision and new technologies. In 2021, researchers found that, verteporfin , an FDA -approved drug for eye disease, could enable scar-free healing in mice. According to the study, the drug works by blocking mechanical stress signals in fibroblast cells. Body mass index Body mass index ( BMI )
288-421: A 7-day window on a monthly basis. All other adult tissues, upon rapid shedding or injury, can scar. Prolonged inflammation , as well as the fibroblast proliferation, can occur. Redness that often follows an injury to the skin is not a scar and is generally not permanent (see wound healing ). The time it takes for this redness to dissipate may, however, range from a few days to, in some serious and rare cases,
384-577: A BMI between the 85th and 95th percentile are considered to be overweight. Studies in Britain from 2013 have indicated that females between the ages 12 and 16 had a higher BMI than males of the same age by 1.0 kg/m on average. These recommended distinctions along the linear scale may vary from time to time and country to country, making global, longitudinal surveys problematic. People from different populations and descent have different associations between BMI, percentage of body fat, and health risks, with
480-402: A BMI of 25 or more is considered overweight and 30 or more is considered obese . In addition to the principle, international WHO BMI cut-off points (16, 17, 18.5, 25, 30, 35 and 40), four additional cut-off points for at-risk Asians were identified (23, 27.5, 32.5 and 37.5). These ranges of BMI values are valid only as statistical categories. BMI is used differently for people aged 2 to 20. It
576-658: A calculator, or indirectly using a lookup table (or chart). The table displays BMI as a function of mass and height and may show other units of measurement (converted to metric units for the calculation). The table may also show contour lines or colours for different BMI categories. The BMI is a convenient rule of thumb used to broadly categorize a person as based on tissue mass ( muscle , fat , and bone ) and height. Major adult BMI classifications are underweight (under 18.5 kg/m ), normal weight (18.5 to 24.9), overweight (25 to 29.9), and obese (30 or more). When used to predict an individual's health, rather than as
672-455: A collagen matrix. This collagen overexpression continues and crosslinks the fiber arrangement inside the collagen matrix, making the collagen dense. This densely packed collagen, morphing into an inelastic whitish collagen scar wall, blocks off cell communication and regeneration; as a result, the new tissue generated will have a different texture and quality than the surrounding unwounded tissue. This prolonged collagen-producing process results in
768-420: A cosmetic problem, keloid scars are only inert masses of collagen and therefore completely harmless and not cancerous. However, they can be itchy or painful in some individuals. They tend to be most common on the shoulders and chest . Hypertrophic scars and keloids tend to be more common in wounds closed by secondary intention. Surgical removal of keloid is risky and may exacerbate the condition and worsening of
864-417: A death rate similar to normal weight people as defined by BMI, while underweight and obese people had a higher death rate. A study published by The Lancet in 2009 involving 900,000 adults showed that overweight and underweight people both had a mortality rate higher than normal weight people as defined by BMI. The optimal BMI was found to be in the range of 22.5–25. The average BMI of athletes
960-493: A few years. Scars form differently based on the location of the injury on the body and the age of the person who was injured. The worse the initial damage is, the worse the scar will generally be. Skin scars occur when the dermis (the deep, thick layer of skin) is damaged. Most skin scars are flat and leave a trace of the original injury that caused them. Wounds allowed to heal secondarily tend to scar worse than wounds from primary closure. An injury does not become
1056-410: A few years. Elevated corticosteroid levels are implicated in striae development. Humans and other placental mammals have an umbilical scar (commonly referred to as a navel ) which starts to heal when the umbilical cord is cut after birth. Egg-laying animals have an umbilical scar which, depending on the species, may remain visible for life or disappear within a few days after birth. A scar
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#17329015086281152-606: A form of body art within some cultures and subcultures. These forms of ritual and non-ritual scarring practices can be found in many groups and cultures around the world. First attested in English in the late 14th century, the word scar derives from a conflation of Old French escharre , from Late Latin eschara , which is the Latinisation of the Greek ἐσχάρα ( eskhara ), meaning "hearth, fireplace", but in medicine "scab, eschar on
1248-415: A fortuna scar. The scarring is created by fibroblast proliferation, a process that begins with a reaction to the clot. To mend the damage, fibroblasts slowly form the collagen scar. The fibroblast proliferation is circular and cyclically, the fibroblast proliferation lays down thick, whitish collagen inside the provisional and collagen matrix, resulting in the abundant production of packed collagen on
1344-437: A genetic connective tissue disorder, such as Ehlers–Danlos syndrome . Stretch marks (technically called striae ) are also a form of scarring. These are caused when the skin is stretched rapidly (for instance during pregnancy , significant weight gain , or adolescent growth spurts ), or when skin is put under tension during the healing process (usually near joints ). This type of scar usually improves in appearance after
1440-534: A given height. The BMI also fails to take into account loss of height through ageing. In this situation, BMI will increase without any corresponding increase in weight. Assumptions about the distribution between muscle mass and fat mass are inexact. BMI generally overestimates adiposity on those with leaner body mass (e.g., athletes) and underestimates excess adiposity on those with fattier body mass. A study in June 2008 by Romero-Corral et al. examined 13,601 subjects from
1536-482: A good general correlation with body fat percentage, and noted that obesity has overtaken smoking as the world's number one cause of death. But it also notes that in the study 50% of men and 62% of women were obese according to body fat defined obesity, while only 21% of men and 31% of women were obese according to BMI, meaning that BMI was found to underestimate the number of obese subjects. A 2010 study that followed 11,000 subjects for up to eight years concluded that BMI
1632-656: A high muscle-to-fat ratio and therefore a BMI that is misleadingly high relative to their body-fat percentage. A common use of the BMI is to assess how far an individual's body weight departs from what is normal for a person's height. The weight excess or deficiency may, in part, be accounted for by body fat ( adipose tissue ) although other factors such as muscularity also affect BMI significantly (see discussion below and overweight ). The WHO regards an adult BMI of less than 18.5 as underweight and possibly indicative of malnutrition , an eating disorder , or other health problems, while
1728-502: A higher risk of type 2 diabetes mellitus and atherosclerotic cardiovascular disease at BMIs lower than the WHO cut-off point for overweight, 25 kg/m , although the cut-off for observed risk varies among different populations. The cut-off for observed risk varies based on populations and subpopulations in Europe, Asia and Africa. The Hospital Authority of Hong Kong recommends the use of
1824-419: A large (or tall) frame and underestimates roughly 10% for a smaller frame (short stature). In other words, people with small frames would be carrying more fat than optimal, but their BMI indicates that they are normal . Conversely, large framed (or tall) individuals may be quite healthy, with a fairly low body fat percentage , but be classified as overweight by BMI. For example, a height/weight chart may say
1920-500: A means to prevent a further increase in BMI. In France, Italy, and Spain, legislation has been introduced banning the usage of fashion show models having a BMI below 18. In Israel, a model with BMI below 18.5 is banned. This is done to fight anorexia among models and people interested in fashion. A study published by Journal of the American Medical Association ( JAMA ) in 2005 showed that overweight people had
2016-554: A more serious form of excessive scarring, because they can grow indefinitely into large, tumorous (although benign) neoplasms . Hypertrophic scars are often distinguished from keloid scars by their lack of growth outside the original wound area, but this commonly taught distinction can lead to confusion. Keloid scars can occur on anyone, but they are most common in dark-skinned people. They can be caused by surgery, cuts, accident, acne or, sometimes, body piercings . In some people, keloid scars form spontaneously. Although they can be
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#17329015086282112-430: A scar until the wound has completely healed; this can take many months, or years in the worst pathological cases, such as keloids. To begin to patch the damage, a clot is created; this clot is the beginning process that results in a provisional matrix. In the process, the first layer is a provisional matrix and is not a scar. Over time, the wounded body tissue overexpresses collagen inside the provisional matrix to create
2208-506: A specific form of scarring of the skin of the abdominal area due to rapid expansion of the uterus as well as sudden weight gain during pregnancy. About 90% of pregnant women are affected. A number of additional factors appear to promote the appearance of stretch marks: one study of 324 women, done just after they had given birth, demonstrated that low maternal age, high body mass index , weight gain over 15 kg (33 pounds) and higher neonatal birth weight were independently correlated with
2304-478: A statistical measurement for groups, the BMI has limitations that can make it less useful than some of the alternatives , especially when applied to individuals with abdominal obesity , short stature , or high muscle mass . BMIs under 20 and over 25 have been associated with higher all-cause mortality, with the risk increasing with distance from the 20–25 range. Adolphe Quetelet , a Belgian astronomer , mathematician, statistician , and sociologist , devised
2400-513: A type of calcium channel blocker, is considered a candidate drug for the treatment of hypertrophic scars. A study conducted by the Catholic University of Korea concluded that verapamil-releasing silicone gel is effective and is a superior alternative to the conventional silicone gel where decreased median SEI, fibroblast count, and collagen density in all verapamil-added treatment groups were observed. Gross morphologic features suggested that
2496-437: A vague means of estimating adiposity . The duality of the BMI is that, while it is easy to use as a general calculation, it is limited as to how accurate and pertinent the data obtained from it can be. Generally, the index is suitable for recognizing trends within sedentary or overweight individuals because there is a smaller margin of error. The BMI has been used by the WHO as the standard for recording obesity statistics since
2592-502: A wound caused by burning or otherwise", and Middle English skar ("cut, crack, incision"), which is from Old Norse skarð ("notch, gap"). The conflation helped to form the English meaning. Compare the place name Scarborough for evolution of skarð to scar . Research, before 2009, focused on scar improvements with research into molecular mechanisms. Treatments involving molecular mechanisms including avotermin, ribosomal s6 kinase (RSK), and osteopontin were investigated at
2688-430: Is 22.4 for women and 23.6 for men. High BMI is associated with type 2 diabetes only in people with high serum gamma-glutamyl transpeptidase . In an analysis of 40 studies involving 250,000 people, patients with coronary artery disease with normal BMIs were at higher risk of death from cardiovascular disease than people whose BMIs put them in the overweight range (BMI 25–29.9). One study found that BMI had
2784-453: Is a value derived from the mass ( weight ) and height of a person. The BMI is defined as the body mass divided by the square of the body height , and is expressed in units of kg/m , resulting from mass in kilograms (kg) and height in metres (m). The BMI may be determined first by measuring its components by means of a weighing scale and a stadiometer . The multiplication and division may be carried out directly, by hand or using
2880-427: Is also being investigated as a potential treatment for stretch marks. Since ancient times, people have sought remedies to prevent stretch marks during pregnancy. Both ancient Greeks and Romans used olive oil , while Ethiopians and Somalis used frankincense . Striae were first recognized by Roederer in 1773, and were later histologically described by Troisier and Ménétrier in 1889. In 1936, Nardelli made
2976-508: Is also used to lessen the appearance of severe glabella lines, though its effectiveness in this application is debatable. Essentially the process involves separating the skin tissue in the affected area from the deeper scar tissue. This allows the blood to pool under the affected area, eventually causing the deep rolling scar to level off with the rest of the skin area. Once the skin has leveled, treatments such as laser resurfacing , microdermabrasion or chemical peels can be used to smooth out
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3072-424: Is calculated in the same way as for adults but then compared to typical values for other children or youth of the same age. Instead of comparison against fixed thresholds for underweight and overweight, the BMI is compared against the percentiles for children of the same sex and age. A BMI that is less than the 5th percentile is considered underweight and above the 95th percentile is considered obese. Children with
3168-512: Is composed of the same collagen as the tissue it has replaced, but the composition of the scar tissue, compared to the normal tissue, is different. Scar tissue also lacks elasticity unlike normal tissue which distributes fiber elasticity . Scars differ in the amounts of collagen overexpressed. Labels have been applied to the differences in overexpression. Two of the most common types are hypertrophic and keloid scarring, both of which experience excessive stiff collagen bundled growth overextending
3264-406: Is convenient to apply, and shows enhanced results. A long-term course of corticosteroid injections into the scar may help flatten and soften the appearance of keloid or hypertrophic scars. Topical steroids are ineffective. However, clobetasol propionate can be used as an alternative treatment for keloid scars. Topical steroid applied immediately after fractionated CO 2 laser treatment
3360-490: Is expressed in kg/m , resulting from mass in kilograms and height in metres. If pounds and inches are used, a conversion factor of 703 (kg/m )/(lb/in ) is applied. (If pounds and feet are used, a conversion factor of 4.88 is used.) When the term BMI is used informally, the units are usually omitted. BMI provides a simple numeric measure of a person's thickness or thinness , allowing health professionals to discuss weight problems more objectively with their patients. BMI
3456-469: Is however very effective (and more efficacious than laser treatment alone) and has shown benefit in numerous clinical studies. Scar revision is a process of cutting the scar tissue out. After the excision, the new wound is usually closed up to heal by primary intention , instead of secondary intention . Deeper cuts need a multilayered closure to heal optimally, otherwise depressed or dented scars can result. Surgical excision of hypertrophic or keloid scars
3552-545: Is no clearly effective treatment, though various methods have been attempted and studied. Striae, or "stretch marks", begin as reddish or purple lesions which can appear anywhere on the body, but are most likely to appear in places where larger amounts of fat are stored. The most common places are the abdomen (especially near the navel ), breasts, upper arms, underarms, back, thighs (both inner and outer), hips, and buttocks. Over time, they tend to atrophy and lose pigmentation . The affected areas appear empty, and are soft to
3648-415: Is not the most appropriate measure for the risk of heart attack, stroke or death. A better measure was found to be the waist-to-height ratio . A 2011 study that followed 60,000 participants for up to 13 years found that waist–hip ratio was a better predictor of ischaemic heart disease mortality. The medical establishment and statistical community have both highlighted the limitations of BMI. Part of
3744-426: Is often associated to other methods, such as pressotherapy or silicone gel sheeting. Lone excision of keloid scars, however, shows a recurrence rate close to 45%. A clinical study is currently ongoing to assess the benefits of a treatment combining surgery and laser-assisted healing in hypertrophic or keloid scars. Subcision is a process used to treat deep rolling scars left behind by acne or other skin diseases. It
3840-423: Is often better calculated using measures of body fat, as determined by such techniques as skinfold measurements or underwater weighing and the limitations of manual measurement have also led to alternative methods to measure obesity, such as the body volume indicator . It is not clear where on the BMI scale the threshold for overweight and obese should be set. Because of this, the standards have varied over
3936-444: Is particularly the case when there is new tissue growth, which can interfere with the underlying physical support of the dermis or epidermis by displacing the supportive tissue. Examples of cases where stretch marks are common include weight gain (in the form of fat and/or muscle ), pregnancy , and adolescent growth spurts , though it is also noted that some medications, as well as other medical conditions and diseases, may increase
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4032-529: Is sometimes used to prevent recurrence of severe keloid and hypertrophic scarring. It is thought to be effective despite a lack of clinical trials, but only used in extreme cases due to the perceived risk of long-term side effects. Silicone scar treatments are commonly used in preventing scar formation and improving existing scar appearance. A meta-study by the Cochrane collaboration found weak evidence that silicone gel sheeting helps prevent scarring. However,
4128-536: Is the product of the body's repair mechanism after tissue injury. If a wound heals quickly within two weeks with new formation of skin, minimal collagen will be deposited and no scar will form. When the extracellular matrix senses elevated mechanical stress loading, tissue will scar, and scars can be limited by stress shielding wounds. Small full thickness wounds under 2mm reepithelize fast and heal scar free. Deep second-degree burns heal with scarring and hair loss . Sweat glands do not form in scar tissue, which impairs
4224-703: The Journal of Chronic Diseases by Ancel Keys and others. In this paper, Keys argued that what he termed the BMI was "if not fully satisfactory, at least as good as any other relative weight index as an indicator of relative obesity". The interest in an index that measures body fat came with observed increasing obesity in prosperous Western societies. Keys explicitly judged BMI as appropriate for population studies and inappropriate for individual evaluation. Nevertheless, due to its simplicity, it has come to be widely used for preliminary diagnoses. Additional metrics, such as waist circumference, can be more useful. The BMI
4320-737: The Engrailed-1 genetic marker. EPFs are the primary contributors to all fibrotic outcomes after wounding. ENFs do not contribute to fibrotic outcomes. Mammalian wounds that involve the dermis of the skin heal by repair, not regeneration (except in 1st trimester inter-uterine wounds and in the regeneration of deer antlers). Full-thickness wounds heal by a combination of wound contracture and edge re-epitheliasation. Partial thickness wounds heal by edge re-epithelialisation and epidermal migration from adnexal structures (hair follicles, sweat glands and sebaceous glands). The site of keratinocyte stem cells remains unknown but stem cells are likely to reside in
4416-622: The Ponderal index is based on the natural scaling of mass with the third power of the height. However, many taller people are not just "scaled up" short people but tend to have narrower frames in proportion to their height. Carl Lavie has written that "The B.M.I. tables are excellent for identifying obesity and body fat in large populations, but they are far less reliable for determining fatness in individuals." For US adults, exponent estimates range from 1.92 to 1.96 for males and from 1.45 to 1.95 for females. The BMI overestimates roughly 10% for
4512-498: The basal layer of the epidermis and below the bulge area of hair follicles. The fibroblast involved in scarring and contraction is the myofibroblast , which is a specialized contractile fibroblast. These cells express α-smooth muscle actin (α-SMA). The myofibroblasts are absent in the first trimester in the embryonic stage where damage heals scar-free; in small incisional or excision wounds less than 2 mm that also heal without scarring; and in adult unwounded tissues where
4608-438: The carbon dioxide laser (CO 2 ) or Er:YAG offer the best results for atrophic and acne scars. Like dermabrasion , ablative lasers work by removing the epidermis. Healing times for ablative therapy are much longer and the risk profile is greater compared to nonablative therapy; however, nonablative therapy offers only minor improvements in cosmetic appearance of atrophic and acne scars. Low-dose, superficial radiotherapy
4704-541: The 1990s the World Health Organization (WHO) decided that a BMI of 25 to 30 should be considered overweight and a BMI over 30 is obese, the standards the NIH set. This became the definitive guide for determining if someone is overweight. One study found that the vast majority of people labelled 'overweight' and 'obese' according to current definitions do not in fact face any meaningful increased risk for early death. In
4800-458: The BMI will be mostly correct when determining a person to be obese, but can err quite frequently when determining a person not to be. Despite this undercounting of obesity by BMI, BMI values in the intermediate BMI range of 20–30 were found to be associated with a wide range of body fat percentages. For men with a BMI of 25, about 20% have a body fat percentage below 20% and about 10% have body fat percentage above 30%. Body composition for athletes
4896-711: The UK, NICE guidance recommends prevention of type 2 diabetes should start at a BMI of 30 in White and 27.5 in Black African , African-Caribbean , South Asian , and Chinese populations. Research since 2021 based on a large sample of almost 1.5 million people in England found that some ethnic groups would benefit from prevention at or above a BMI of (rounded): In 1998, the U.S. National Institutes of Health brought U.S. definitions in line with World Health Organization guidelines, lowering
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#17329015086284992-465: The United States' third National Health and Nutrition Examination Survey (NHANES III) and found that BMI-defined obesity (BMI ≥ 30) was present in 21% of men and 31% of women. Body fat-defined obesity was found in 50% of men and 62% of women. While BMI-defined obesity showed high specificity (95% for men and 99% for women), BMI showed poor sensitivity (36% for men and 49% for women). In other words,
5088-583: The appearance of stretch marks. Topical tretinoin is categorized by the United States Food and Drug Administration (FDA) as a known teratogen (causing malformations in fetuses) in animals, without adequate human studies on safety in pregnancy. Carboxytherapy is a known procedure; however, there is a lack of evidence to support how effective it is. Research into a new skin grafting technique called "microcolumn grafting / micrografting", which uses needles to take autologous full-thickness skin biopsies ,
5184-472: The basis of the BMI between 1830 and 1850 as he developed what he called "social physics". Quetelet himself never intended for the index, then called the Quetelet Index, to be used as a means of medical assessment. Instead, it was a component of his study of l'homme moyen , or the average man. Quetelet thought of the average man as a social ideal, and developed the body mass index as a means of discovering
5280-407: The belly, these striae also commonly occur on the breasts, thighs, hips, lower back, and buttocks. Pregnancy-related striae are known as striae gravidarum . Striae may also be influenced by the hormonal changes associated with puberty, pregnancy, bodybuilding , or hormone replacement therapy . There is no evidence that creams used during pregnancy prevent stretch marks. Once they have formed, there
5376-405: The body overproduces collagen , which causes the scar to be raised above the surrounding skin. Hypertrophic scars take the form of a red raised lump on the skin for lighter pigmented skin and the form of dark brown for darker pigmented skin. They usually occur within 4 to 8 weeks following wound infection or wound closure with excess tension and/or other traumatic skin injuries. Keloid scars are
5472-434: The body's ability to function normally and repair itself. However, some people dislike the way stretch marks look. Young women are generally affected the most and often seek treatment for them from a dermatologist and following pregnancy . Stretch marks appear to be caused by stretching of the skin. This is especially true when there is an increase in cortisone – an increase in cortisone levels can increase
5568-566: The body. Mechanical distension and rapidly developing areas of the body during pregnancy (such as the abdomen, breasts, and thighs) are most commonly associated with striae formation. Some have suggested that relaxin and estrogen combined with higher levels of cortisol during pregnancy can cause an accumulation of mucopolysaccharides , which increases water absorption of connective tissue , making it prime for tearing under mechanical stress . There also seems to be an association between higher body mass indices and in women with bigger babies and
5664-480: The combination of verapamil and silicone improves the overall quality of hypertrophic scars by reducing scar height and redness. This was verified with quantifiable histomorphometric parameters; however, oral verapamil is not a good choice because of its effect of lowering blood pressure. Intralesional injection of verapamil is also suboptimal because of the required frequency for injections. Topical silicone gel combined with verapamil does not lead to systemic hypotension,
5760-657: The early 1980s. This general correlation is particularly useful for consensus data regarding obesity or various other conditions because it can be used to build a semi-accurate representation from which a solution can be stipulated, or the RDA for a group can be calculated. Similarly, this is becoming more and more pertinent to the growth of children, since the majority of children are sedentary. Cross-sectional studies indicated that sedentary people can decrease BMI by becoming more physically active. Smaller effects are seen in prospective cohort studies which lend to support active mobility as
5856-474: The edge of small/medium or medium/large, common sense should be used in calculating one's ideal weight. However, falling into one's ideal weight range for height and build is still not as accurate in determining health risk factors as waist-to-height ratio and actual body fat percentage. Accurate frame size calculators use several measurements (wrist circumference, elbow width, neck circumference, and others) to determine what category an individual falls into for
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#17329015086285952-440: The epidermis in a controlled manner, leading to exfoliation and the alleviation of certain skin conditions, including superficial acne scars. Various chemicals can be used depending upon the depth of the peel, and caution should be used, particularly for dark-skinned individuals and those individuals susceptible to keloid formation or with active infections. Filler injections of collagen can be used to raise atrophic scars to
6048-410: The fibers giving scars their uneven texture. Over time, the fibroblasts continue to crawl around the matrix, adjusting more fibers and, in the process, the scarring settles and becomes stiff. This fibroblast proliferation also contracts the tissue. In unwounded tissue, these fibers are not overexpressed with thick collagen and do not contract. EPF and ENF fibroblasts have been genetically traced with
6144-421: The fibroblast in itself is arrested; however, the myofibroblast is found in massive numbers in adult wound healing which heals with a scar. The myofibroblasts make up a high proportion of the fibroblasts proliferating in the postembryonic wound at the onset of healing. In the rat model, for instance, myofibroblasts can constitute up to 70% of the fibroblasts, and is responsible for fibrosis on tissue. Generally,
6240-420: The first morphologically correct descriptions. Medical terminology for these kinds of markings includes: striae atrophicae, vergetures, stria distensae, striae cutis distensae, lineae atrophicae, linea albicante, or simply striae. Scar A scar (or scar tissue ) is an area of fibrous tissue that replaces normal skin after an injury . Scars result from the biological process of wound repair in
6336-538: The first pregnancy do not develop them during later pregnancies. Genetic factors such as genealogy and race also seem to be predictive in the appearance of striae. Collagen and elastin are proteins in the skin that contribute to the skin's strength, resilience, flexibility, and help skin that has been stretched to recover its original state. Boosting the production of collagen and elastin helps prevent stretch marks from occurring. Stretch marks can also derive from nutritional deficiencies . Consuming foods that contribute to
6432-757: The following BMI ranges: A 2000 study from the Japan Society for the Study of Obesity (JASSO) presents the following table of BMI categories: In Singapore, the BMI cut-off figures were revised in 2005 by the Health Promotion Board (HPB), motivated by studies showing that many Asian populations, including Singaporeans, have a higher proportion of body fat and increased risk for cardiovascular diseases and diabetes mellitus , compared with general BMI recommendations in other countries. The BMI cut-offs are presented with an emphasis on health risk rather than weight. In
6528-438: The ideal weight (BMI 21.5) for a 1.78-metre-tall (5 ft 10 in) man is 68 kilograms (150 lb). But if that man has a slender build (small frame), he may be overweight at 68 kg or 150 lb and should reduce by 10% to roughly 61 kg or 135 lb (BMI 19.4). In the reverse, the man with a larger frame and more solid build should increase by 10%, to roughly 75 kg or 165 lb (BMI 23.7). If one teeters on
6624-666: The incidence and severity of striae. Also, younger women seem to be at higher risk of developing striae during pregnancy. The prevalence and severity of striae gravidarum varies among populations. The current literature suggest that in the general population of the United States, there is a 50% to 90% prevalence of striae associated with pregnancy, partly as a result of the normal hormonal changes associated with pregnancy and partly due to stretching of skin fibers. Many women experience striae gravidarum during their first pregnancy. Nearly 45% percent of women develop striae gravidarum before 24 weeks of gestation. Many women who develop lesions during
6720-418: The keloid. An atrophic scar takes the form of a sunken recess in the skin, which has a pitted appearance. These are caused when underlying structures supporting the skin, such as fat or muscle , are lost. This type of scarring is often associated with acne, chickenpox , other diseases (especially Staphylococcus infection), surgery, certain insect and spider bites, or accidents. It can also be caused by
6816-439: The level of surrounding skin. Risks vary based upon the filler used, and can include further disfigurement and allergic reaction . Nonablative lasers, such as the 585 nm pulsed dye laser , 1064 nm and 1320 nm Nd:YAG , or the 1540 nm Er:Glass are used as laser therapy for hypertrophic scars and keloids. There is tentative evidence for burn scars that they improve the appearance. Ablative lasers such as
6912-426: The likelihood of stretch marks appearing. Common medications that can contribute to stretch marks include " corticosteroid creams, lotions and pills and chronic use of oral or systemic steroids ". Medical conditions that can contribute to stretch marks include Ehlers–Danlos syndrome , Cushing's syndrome , Marfan syndrome , and adrenal gland diseases . Pregnancy stretch marks, also known as striae gravidarum , are
7008-498: The myofibroblasts disappear from the wound within 30 days, but can remain in pathological cases in hypertrophy , such as keloids. Myofibroblasts have plasticity and in mice can be transformed into fat cells, instead of scar tissue, via the regeneration of hair follicles. Wounds under 2mm generally do not scar but larger wounds generally do scar. In 2011 it was found that mechanical stress can stimulate scarring and that stress shielding can reduce scarring in wounds. In 2021 it
7104-651: The normal/overweight cut-off from a BMI of 27.8 (men) and 27.3 (women) to a BMI of 25. This had the effect of redefining approximately 25 million Americans, previously healthy , to overweight . This can partially explain the increase in the overweight diagnosis in the past 20 years , and the increase in sales of weight loss products during the same time. WHO also recommends lowering the normal/overweight threshold for southeast Asian body types to around BMI 23, and expects further revisions to emerge from clinical studies of different body types. A survey in 2007 showed 63% of Americans were then overweight or obese, with 26% in
7200-482: The obese category (a BMI of 30 or more). By 2014, 37.7% of adults in the United States were obese, 35.0% of men and 40.4% of women; class 3 obesity (BMI over 40) values were 7.7% for men and 9.9% for women. The U.S. National Health and Nutrition Examination Survey of 2015-2016 showed that 71.6% of American men and women had BMIs over 25. Obesity—a BMI of 30 or more—was found in 39.8% of the US adults. The BMI ranges are based on
7296-447: The occurrence of striae. Teenagers were found to be at the highest risk of developing severe striae. These skin marks are symptoms of pregnancy caused by the tearing of the dermis , resulting in atrophy and loss of rete ridges . These scars often appear as reddish or bluish streaks on the abdomen, and can also appear on the breasts and thighs. Some of these striae disappear with time, while others remain as permanent discolorations of
7392-470: The past few decades. Between 1980 and 2000 the U.S. Dietary Guidelines have defined overweight at a variety of levels ranging from a BMI of 24.9 to 27.1. In 1985 the National Institutes of Health (NIH) consensus conference recommended that overweight BMI be set at a BMI of 27.8 for men and 27.3 for women. In 1998, an NIH report concluded that a BMI over 25 is overweight and a BMI over 30 is obese. In
7488-430: The probability or severity of stretch marks by reducing the skin's pliability. More specifically, it affects the dermis by preventing the fibroblasts from forming collagen and elastin fibers necessary to keep rapidly growing skin taut; this can create a lack of supportive material as the skin is stretched, and lead to dermal and epidermal tearing, which in turn can produce scarring in the form of stretch marks. This
7584-415: The regulation of body temperature. Elastic fibers are generally not detected in scar tissue younger than 3 months old. In scars, rete pegs are lost; through a lack of rete pegs, scars tend to shear easier than normal tissue. The endometrium , the inner lining of the uterus, is the only adult tissue to undergo rapid cyclic shedding and regeneration without scarring, shedding and restoring roughly inside
7680-419: The relationship between body weight and disease and death. Overweight and obese individuals are at an increased risk for the following diseases: Among people who have never smoked, overweight/obesity is associated with 51% increase in mortality compared with people who have always been a normal weight. The BMI is generally used as a means of correlation between groups related by general mass and can serve as
7776-434: The same body shape and relative composition have a larger BMI. BMI is proportional to the mass and inversely proportional to the square of the height. So, if all body dimensions double, and mass scales naturally with the cube of the height, then BMI doubles instead of remaining the same. This results in taller people having a reported BMI that is uncharacteristically high, compared to their actual body fat levels. In comparison,
7872-446: The same protein ( collagen ) as the tissue that it replaces, but the fiber composition of the protein is different; instead of a random basketweave formation of the collagen fibers found in normal tissue, in fibrosis the collagen cross-links and forms a pronounced alignment in a single direction. This collagen scar tissue alignment is usually of inferior functional quality to the normal collagen randomised alignment. For example, scars in
7968-428: The scale is often biased. As noted by sociologist Sabrina Strings, the BMI is largely inaccurate for black people especially, disproportionately labelling them as overweight even for healthy individuals. The exponent in the denominator of the formula for BMI is arbitrary. The BMI depends upon weight and the square of height. Since mass increases to the third power of linear dimensions, taller individuals with exactly
8064-443: The scarred tissue. Research shows the use of vitamin E and onion extract (sold as Mederma ) as treatments for scars is ineffective. Vitamin E causes contact dermatitis in up to 33% of users and in some cases it may worsen scar appearance and could cause minor skin irritations, but Vitamin C and some of its esters fade the dark pigment associated with some scars. The permanence of scarring has led to its intentional use as
8160-452: The scars after pregnancy is limited. There are no clearly useful treatments for stretch marks, although there are many different suggestions on how to remove them or lessen their appearance. Various efforts that have been tried including laser treatments , glycolic acid , and microdermabrasion . Tretinoin (0.1% w/w), which is a retinoid , has found to be effective on early stretch marks in several studies. Hyaluronic acid also improves
8256-438: The skin are less resistant to ultraviolet radiation , and sweat glands and hair follicles do not grow back within scar tissues. A myocardial infarction , commonly known as a heart attack, causes scar formation in the heart muscle, which leads to loss of muscular power and possibly heart failure . However, there are some tissues (e.g. bone ) that can heal without any structural or functional deterioration. All scarring
8352-408: The skin's health, such as zinc -rich foods, protein-rich foods, and foods high in vitamin A, C, and D, can help suppress stretch marks. A systematic review has not found evidence that creams and oils are useful for preventing or reducing stretch marks in pregnancy. The safety in pregnancy of one ingredient, Centella asiatica , has been questioned. Evidence on treatments for reducing the appearance of
8448-403: The skin, as well as in other organs , and tissues of the body. Thus, scarring is a natural part of the healing process. With the exception of very minor lesions , every wound (e.g., after accident , disease , or surgery ) results in some degree of scarring. An exception to this are animals with complete regeneration , which regrow tissue without scar formation. Scar tissue is composed of
8544-531: The socially ideal human person. According to Lars Grue and Arvid Heiberg in the Scandinavian Journal of Disability Research, Quetelet's idealization of the average man would be elaborated upon by Francis Galton a decade later in the development of Eugenics . The modern term "body mass index" (BMI) for the ratio of human body weight to squared height was coined in a paper published in the July 1972 edition of
8640-469: The statistical limitations of the BMI scale is the result of Quetelet's original sampling methods. As noted in his primary work, A Treatise on Man and the Development of His Faculties, the data from which Quetelet derived his formula was taken mostly from Scottish Highland soldiers and French Gendarmerie . The BMI was always designed as a metric for European men. For women, and people of non-European origin,
8736-446: The studies examining it were of poor quality and susceptible to bias. Pressure dressings are commonly used in managing burn and hypertrophic scars, although supporting evidence is lacking. Care providers commonly report improvements, however, and pressure therapy has been effective in treating ear keloids. The general acceptance of the treatment as effective may prevent it from being further studied in clinical trials. Verapamil ,
8832-610: The time. After successful phase I/II trials , human recombinant TGF-β3 (avotermin, planned trade name Juvista) failed in Phase III trials. In 2011, the scientific literature highlighted stress shielding a fresh wound through the wound healing process, brings significant scar improvement and smaller scars. By 2016, skin had been regenerated in vivo and in vitro . and scar-free healing had been operationalized and induced by four main regeneration techniques: by instrument, by materials, by drugs, and by in vitro 3-D printing. In 2018,
8928-450: The tissue, blocking off regeneration of tissues. Another form is atrophic scarring (sunken scarring), which also has an overexpression of collagen blocking regeneration. This scar type is sunken, because the collagen bundles do not overextend the tissue. Stretch marks (striae) are regarded as scars by some. High melanin levels and either African or Asian ancestry may make adverse scarring more noticeable. Hypertrophic scars occur when
9024-449: The touch. Stretch marks occur in the dermis , the resilient middle tissue layer that helps the skin retain its shape. No stretch marks will form as long as there is support within the dermis; stretching plays a role in where the marks occur and in what direction they run. They can (but do not always) cause a burning and itching sensation, as well as emotional distress. They pose no inherent health risk on their own, and do not compromise
9120-430: Was designed to be used as a simple means of classifying average sedentary (physically inactive) populations, with an average body composition . For such individuals, the BMI value recommendations as of 2014 are as follows: 18.5 to 24.9 kg/m may indicate optimal weight, lower than 18.5 may indicate underweight , 25 to 29.9 may indicate overweight , and 30 or more may indicate obese . Lean male athletes often have
9216-445: Was found that using chemicals to manipulate fibroblasts to not sense mechanical stress brought scar-free healing. The scar-free healing also occurred when mechanical stress was placed onto a wound. Early and effective treatment of acne scarring can prevent severe acne and the scarring that often follows. In 2004, no prescription drugs for the treatment or prevention of scars were available. Chemical peels are chemicals which destroy
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