20.7 21.9 25.6 31.8 36.0 38.9 42.0 30–39 19.8 21.1 22.0 23.3 27.6 33.1 36.6 40.0 44.7 40–49 20.0 21.5 22.5 23.7 28.1 33.4 37.0 39.6 44.5 50–59 19.9 21.5 22.2 24.5 28.6 34.4 38.3 40.7 45.2 60–69 20.0 21.7 23.0 24.5 28.9 33.4 36.1 38.7 41.8 70–79 20.5 22.1 22.9 24.6 28.3 33.4 36.5 39.1 42.9 ≥ 80 19.3 20.4 21.3 23.3 26.1 29.7 30.9 32.8 35.2 consequences of elevated level in adults the bmi ranges are based on the relationship between body weight and disease and death. overweight and obese individuals are at an increased risk for the following diseases: coronary artery disease dyslipidemia type 2 diabetes gallbladder disease hypertension osteoarthritis sleep apnea stroke infertility at least 10 cancers, including endometrial, breast, and colon cancer epidural lipomatosis 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. applications public health the bmi is generally used as a means of correlation between groups related by general mass and can serve as 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 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 a means to prevent a further increase in bmi. legislation in france, italy, and spain, legislation has been introduced banning the usage of fashion show models having a bmi below 18. in israel, a bmi below 18.5 is banned. this is done to fight anorexia among models and people interested in fashion. relationship to health a study published by journal of the american medical association (jama) in 2005 showed that overweight people had 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 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 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 is not a good 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. limitations this graph shows the correlation between body mass index (bmi) and body fat percentage (bfp) for 8550 men in nchs' nhanes 1994 data. data in the upper left and lower right quadrants suggest the limitations of bmi. the medical establishment and statistical community have both highlighted the limitations of bmi. part of the statistical limitations of the bmi scale is the result of quetelet's original sampling methods. as noted in his original 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, the scale is often biased. as noted by sabrina strings in her book fearing the black body: the racial origins of fat phobia, the bmi is largely inaccurate for black people especially, disproportionately labelling them as overweight even for healthy individuals. scaling 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 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, 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. physical characteristics the bmi overestimates roughly 10% for 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 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 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 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. muscle versus fat 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 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, 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 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 new, alternative methods to measure obesity, such as the body volume indicator. variation in definitions of categories 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 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 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. the current who and nih ranges of normal weights are proved to be associated with decreased risks of some diseases such as diabetes type ii; however using the same range of bmi for men and women is considered arbitrary and makes the definition of underweight quite unsuitable for men. 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 a quantitative analysis of several studies, involving more than 600,000 men and women, the lowest mortality rates were found for people with bmis between 23 and 29; most of the 25–30 range considered 'overweight' was not associated with higher risk. alternatives corpulence index (exponent of 3) the corpulence index uses an exponent of 3 rather than 2. the corpulence index yields valid results even for very short and very tall people, which is a problem with bmi. for example, a 152.4 cm (5 ft 0 in) tall person at an ideal body weight of 48 kg (106 lb) gives a normal bmi of 20.74 and ci of 13.6, while a 200 cm (6 ft 7 in) tall person with a weight of 100 kg (220 lb) gives a bmi of 24.84, very close to an overweight bmi of 25, and a ci of 12.4, very close to a normal ci of 12. new bmi (exponent of 2.5) the exponent of 5/2 was proposed by quetelet himself in the 19th century: in general, we do not err much when we assume that during development the squares of the weight at different ages are as the fifth powers of the height however, it was not used much later, until the following formula for computing body mass index that accounts for the distortions of the traditional bmi formula for shorter and taller individuals has been proposed by nick trefethen, professor of numerical analysis at the university of oxford: b m i new = 1.3 × mass kg height m 2.5 _=1.3\times __^ the scaling factor of 1.3 was determined to make the