Body mass index, or BMI, may be a useful gizmo for determining healthful weight, but experts have expressed uncertainty about its reliability.
BMI alone cannot show whether a person’s weight is healthful, but using it together with other indicators can provide a more complete picture.
Age and sex
For adults ages 20 years and older, BMI incorporates weight and height, but it doesn’t take age or sex under consideration .
A woman tends to possess more body fat than a person with an equivalent BMI. Likewise, an older person tends to possess more body fat than a younger person with an equal BMI.
For these reasons, BMI might not give the detail necessary to work out whether a person’s weight is healthful.
BMI doesn’t reflect the situation or amount of body fat, and these factors can impact health.
For example, studies have indicated that folks who have fat round the waist and surrounding the abdominal organs could also be more in danger of health problems than those with fat in other areas.
A 5-year investigation of 1,964 people, published in Scientific Reports in 2017, was one studyTrusted Source that confirmed these findings.
BMI and health
If an individual features a high BMI, they’re likely to possess a high proportion of body fat, especially if their BMI falls within the obesity category.
However, it’s possible to be “overweight” consistent with BMI, but have healthful levels of fat.
For extremely muscular people, like athletes and bodybuilders, height and weight measurements alone might not accurately indicate health, because muscle weighs quite fat.
A healthy, muscular person may have a BMI during a very high range. Meanwhile, a frail, inactive person may have a coffee BMI, but more body fat and fewer lean tissue than is healthful.
Stages of development
Regular BMI cannot accurately indicate the state of a person’s health at some stages in life.
- pregnancy and breastfeeding
- childhood and adolescence, while an individual remains growingF
or this reason, BMI calculations are different for youngsters and teenagers . These measurements take age and sex under consideration .
Norm also can vary among people of certain races and ethnicities.
Making BMI accurate
The National Heart, Lung, and Blood Institute (NHLBI) suggest that an assessment of weight and health risks should incorporate three key measures:
- waist circumference
- risk factors for diseases and conditions related to obesity
If fat accumulates round the waist instead of the hips, an individual may have a better risk of heart condition and sort 2 diabetes.
This risk increases with a waist size greater than 35 inchesTrusted Source for non-pregnant women or greater than 40 inches for men, consistent with the Centers for Disease Control and Prevention (CDC).
To measure their waist, an individual should:
- Place a tape around their middle, just above the hip bones and therefore the naval.
- Take the measurement just after exhalation .
Weight, obesity, and health risks
The following information, adapted from the NHLBI, may help indicateTrusted Source the risks related to BMI and waist circumference.
The chart shows weight categories consistent with BMI, and therefore the effects of upper waist circumference on the risks of type 2 diabetes, hypertension, and disorder .
Classification BMI (kg/m2) Obesity class Waist Waist
Men 40 inches or lessWomen 35 inches or less Men: 40 inches or moreWomen: 35 inches or more
Underweight 18.4 or less
Healthful weight 18.5–24.9
Overweight 25.0–29.9 Increased risk High risk
Obesity 30.0–34.9 I High risk Very high risk
35.0–39.9 II Very high risk Very high risk
Extreme obesity 40.0+ III Extremely high risk Extremely high risk
A doctor can also measure body fat composition.
Being overweight or having obesity can increase the danger to the guts.
The following issues also can increase the danger of developing heart condition , for instance .
- high vital sign (hypertension)
- high levels of LDL (“bad”) cholesterol
- low levels of HDL (“good”) cholesterol
- high levels of triglycerides
- high blood glucose levels
- a case history of early heart condition
- physical inactivity
- cigarette smoking
- a high consumption of alcohol
A doctor will recommend that an individual consider losing weight if they:
- have a BMI of 30 or greater
- have a BMI of 25–29.9 plus two or more risk factors
If an individual has obesity or excess weight plus two or more risk factors, they’ll be in danger of variety of obesity-related health problems within the future.
Losing 5–10 percentTrusted Source of their current weight can reduce the danger of developing these health problems.
Some people are overweight but haven’t any other risk factors, like high cholesterol or high vital sign . they ought to follow a healthful and varied diet, and obtain regular exercise to stop additional weight gain.