Physique mass index or BMI has lengthy been the usual for measuring well being. The straightforward system is broadly used to categorise whether or not our weight falls inside a “wholesome” vary for our peak. BMI offers an estimate of an individual’s total illness threat, and is used world wide to measure weight problems.
However BMI has come below criticism as a result of it may be inaccurate in estimating physique fats and doesn’t present a full image of an individual’s well being. Analysis additionally reveals that counting on BMI alone to foretell an individual’s threat of well being issues will be deceptive.
The system for calculating BMI was first invented in 1832 by Belgian mathematician and astronomer Adolphe Quetelet. To calculate it, you divide weight in kilograms by peak in metres squared (kg/m2). In adults, BMI is categorised as follows:
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BMI is a fast, straightforward, and low cost manner of diagnosing chubby or weight problems needing solely a weight and peak measurement. Since weight problems carries an elevated threat of illness, together with coronary heart illness, stroke, and diabetes, BMI can establish these at larger threat of creating well being issues. It’s additionally typically used to make choices about who will get sure therapies, and to guage how efficient sure weight reduction interventions are.
However BMI alone doesn’t give a full image of an individual’s well being threat, because it’s merely a measure of physique measurement – not of illness or well being. BMI doesn’t truly measure physique fats, a key ingredient when establishing well being threat. Though it offers a tough indication of physique fats, it doesn’t distinguish between weight coming from fats versus muscle.
Excessive-performance athletes – corresponding to rugby gamers or sprinters – can be categorized as “chubby” or “overweight” by their BMI due to their larger muscle mass. BMI alone would make it seem athletes are at the same threat of the identical well being issues as somebody who’s chubby – despite the fact that analysis reveals energetic individuals have higher ldl cholesterol, blood strain, and decrease blood sugar ranges than somebody who’s inactive.
BMI additionally doesn’t inform us something about the place physique fats is distributed. Physique fats saved across the stomach (an “apple” form) poses a larger well being threat than physique fats saved across the hips. This “apple” form is related to an elevated chance of creating metabolic syndrome. This can be a mixture of associated situations – corresponding to hypertension, excessive blood glucose, and excessive levels of cholesterol – all of which enhance the chance of coronary heart illness, stroke and kind 2 diabetes.
BMI classes are additionally considerably arbitrary. A examine of 13,601 adults confirmed the prevalence of weight problems was a lot decrease when defining weight problems utilizing BMI as an alternative of physique fats proportion. Utilizing BMI classes, much less individuals had been discovered to have weight problems – although many would have been identified as such due to their physique fats proportion.
These classes could also be even much less correct in predicting well being dangers in individuals from ethnic minority backgrounds and older age teams. For instance, Asian persons are at larger threat of creating sort 2 diabetes and coronary heart illness at decrease BMIs than Caucasian individuals. This can be on account of a better physique fats proportion at related BMIs, and/or a larger tendency to retailer fats across the stomach.
Analysis additionally reveals that in adults aged 65 and over, having a BMI throughout the “chubby” class wasn’t related to a larger threat of loss of life whereas a BMI under 23 was. So regular ranges might not work nicely for predicting well being dangers in older individuals.
Individuals can even have a “regular” BMI however have an elevated threat of coronary heart illness and kind 2 diabetes, relying on elements corresponding to their blood strain or physique fats distribution. Measuring waist circumference and physique fats proportion could also be extra helpful in such circumstances.
Dependable, inexpensive and correct indicators of well being standing are essential. BMI is straightforward to measure and offers a tough estimate of illness threat. However whereas it’s a superb start line, BMI must be used alongside different measurements to get a fuller image of an individual’s distinctive well being threat. Way of life elements (corresponding to smoking, bodily exercise, weight-reduction plan and stress ranges), and blood strain, blood sugar and blood levels of cholesterol ought to all be thought-about alongside BMI to ascertain well being threat.
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Waist measurements (corresponding to waist circumference and waist-to-hip ratio) can estimate stomach physique fats – however they are often troublesome to undertake and fewer correct in individuals with a BMI larger than 35. Instruments that break down physique composition – corresponding to bioelectrical impedance evaluation and dual-energy X-ray absorptiometry – work higher. However these will be very costly, time-consuming and sophisticated to make use of – and wouldn’t be sensible for on a regular basis use by GPs.
Staging instruments might present a extra tailor-made evaluation of well being threat and early loss of life in individuals residing with weight problems. These are scoring methods which take into consideration metabolic, bodily and psychological well being to categorise well being threat. They’re designed for use alongside BMI to establish individuals who would profit most from weight administration interventions.
Whereas BMI offers a handy and easy instrument for understanding illness threat, it doesn’t present a full or fully correct image of every thing that influences our well being. Utilizing different measurement instruments alongside BMI can present a extra full image of well being and illness threat – and may assist information choices about the very best well being interventions to make use of for a selected individual.