18 or lower: underweight. 18.5 to 24.9: normal, healthy weight. 25 to 29.9: overweight. 30 or higher: obese.
Your body mass index, or BMI, is the relationship between your weight and your height. A BMI of 20-25 is ideal; 25-30 is overweight and over 30 is obese. If your BMI is under 18.5, you're considered underweight. If your BMI is 18.5-20, you're a bit underweight and can't afford to lose more.
The World Health Organisation (WHO) defines a healthy adult BMI as being between 18.5 and 25. A BMI less than 18.5 indicates underweight (possibly caused by disease, malnutrition or eating disorders such as anorexia nervosa) and a BMI over 25 as overweight (possibly caused by poor diet choices or lack of exercise).
below 18.5 is underweight. between 18.5 and 24.9 is healthy. between 25 and 29.9 is overweight. of 30 or over is obese.
A body mass index of anything under 18.5 is considered underweight and can have potential health consequences, just like a BMI that's considered obesity. Speak with your doctor if you have a BMI of 16 because this is dangerously low.
In males, a BMI of around 13 appears to be fatal. The coefficient of variation (CV) of the BMI is 8.7%. In contrast, females survive to a lower BMI of around 11, although with greater index variability (CV 14%). Several females had BMI's as low as 9 and 10.
There are also different tiers of anorexia based on BMI ranging from mild (<17.5), moderate (16-16.99), and severe (15-15.99), to extreme (<15). A BMI below 13.5 can lead to organ failure, while a BMI below 12 can be life-threatening.
A BMI <16.0 is known to be associated with a markedly increased risk for ill-health, poor physical performance, lethargy and even death; therefore, this cut-off point is a valid extreme limit.
Moderate and severe thinness – A BMI <17.0 indicates moderate and severe thinness in adult populations. It has been clearly linked to increases in illness in adults studied in three continents; therefore, it is a reasonable value to choose as a cut-off point for moderate risk.
Normal BMI is between 18.5 and 24.9.
This is calculated using your weight and your height. In adults, a healthy weight range is a BMI of 18.5 to 24.9. If your BMI is under 18.5 then you would be considered underweight. Note that BMI calculations do not apply in the same way to some people.
Signs and symptoms of malnutrition
a low body weight – people with a body mass index (BMI) under 18.5 are at risk of being malnourished (use the BMI calculator to work out your BMI)
This beauty ideal became de rigueur in the industry; the average runway model has a body mass index (BMI) of 16, which the World Health Organization classifies as severely thin.
Being small, or even underweight according to the numbers, doesn't mean you need to gain weight. A healthy weight isn't necessarily “seen” and not a sign that something is wrong or that a person has an eating disorder.
A normal BMI for an adult is 18.5-25. Above that you are overweight and below that you are underweight. Adults with anorexia have a BMI below 17.5. If you are under 18 years of age, normal weight is assessed by using special age-related BMI charts.
BMI ranges
under 18.5 – This is described as underweight. between 18.5 and 24.9 – This is described as the 'healthy range'. between 25 and 29.9 – This is described as overweight. between 30 and 39.9 – This is described as obesity.
If your BMI is less than 18.5, it falls within the underweight range. If your BMI is 18.5 to 24.9, it falls within the Healthy Weight range. If your BMI is 25.0 to 29.9, it falls within the overweight range.
Can a low BMI affect my fertility? Yes. Having a BMI below 18.5 is classed as underweight, which can make it harder to get pregnant. Having a low BMI can also cause your periods to become irregular or stop.
When looking at average BMI, three countries tie for the least obese country in the world, with an average BMI of 21.1: Madagascar, Eritrea, and Ethiopia.
Risks of being underweight (low BMI)
If you are underweight (BMI less than 18.5kg/m2), you may be malnourished and develop: compromised immune function. respiratory disease. digestive diseases.
A body mass index, or BMI, below 18.5 means a person is underweight and this is associated with health complications such as bone loss, decreased immunity, cardiac problems, and infertility.
For this reason, doctors normally consider 40 to 50 per cent weight loss as life-threatening, regardless of your initial body weight. Total starvation is normally fatal in eight to 12 weeks.
Infrequent Periods
The greater your BMI (particularly in the obese range over 35), the more likely you are to miss your period. It is even possible to stop bleeding altogether, a condition known as secondary amenorrhea.