A BMI below 13.5 can lead to organ failure, while a BMI below 12 can be life-threatening.
A BMI of less than 18.5 is underweight. The researchers analyzed 3.6 million adults and found that a BMI of 21 to 25 is associated with the lowest risk of morbidity. People with BMIs outside this range, both higher and lower, are at risk for more diseases and more at risk for death.
Body mass index (BMI) is an indicator in the diagnosis of anorexia, and BMI <15 kg/m² defines an extreme state in a patient. Data from a literature review and clinical practice show that a BMI <10 kg/m² is not uncommon.
According to the DSM-5, BMI criteria for anorexia nervosa (AN) or “anorexia BMI” requires that someone have a BMI of less than 18.5.
Low Body Weight
The Academy of Eating Disorders recommends inpatient treatment for anyone at or below 75% of their ideal body weight. This is a general suggestion for medical professionals, not a hard and fast rule.
End-stage anorexia nervosa is anorexia nervosa in its most dangerous and severe form. Those experiencing end-stage anorexia present as severely underweight with a BMI of less than 15, are suffering the physical and psychological effects of severe starvation, and require immediate life-saving medical interventions [2].
A BMI nearing 15 is usually used as an indicator for starvation and the health risks involved, with a BMI <17.5 being one of the DSM criteria for the diagnosis of anorexia nervosa.
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.
To interpret the final number, a BMI: below 18.5 means a person is underweight. between 18.5 and 24.9 means a person is of a “normal,” or healthy, weight. between 25 and 29.9 indicates a person is overweight.
A BMI below 13.5 can lead to organ failure, while a BMI below 12 can be life-threatening.
Ranges for BMI include: Underweight: less than 18.5. Normal/healthy weight: 18.5 to 24.9. Overweight: 25.0 to 29.9.
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) a lack of interest in eating and drinking. feeling tired all the time.
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).
How do I know if I'm underweight? 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.
In anorexia, death from organ failure or myocardial infarction is fairly common (up to 20 percent of cases end this way) and tends to happen when body weight has fallen to between 60 and 80 pounds (although it can occur at any time).
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. Five other countries have average BMIs under 22: Timor-Leste (21.3), Burundi (21.6), Japan (21.8), China (21.9) and India (21.9).
BMI <18.5: underweight. BMI 18.5–24.9: normal weight. BMI ≥25.0: overweight. BMI ≥30.0: obesity.
From a clinical perspective, an individual is considered “too skinny” if they are deemed underweight. According to the Centers for Disease Control, an individual is underweight if their Body Mass Index (BMI) is below 18.5 [1].
Anorexia vs Bulimia BMI
The APA does not have BMI requirements for bulimia or other eating disorders. It's only anorexia that BMI is considered important. This means that someone with bulimia could have a normal BMI, but could still be unhealthy because of the impact of bulimic behaviors on their body.
Extreme anorexia is the most serious form of anorexia. It occurs when a person is severely underweight and malnourished from intentionally starving themselves to lower their weight.
The American Dietetic Association (ADA) defines the ideal body mass index (BMI) as between 20 and 25. Thus, anyone below that range would be considered underweight and those with a BMI from 18.5 to 17.5 extremely underweight.
Women with a BMI of less than 18.5 are considered underweight. The average woman's height is 5 feet, 4 inches. If you weigh 107 pounds or less at this height, you are considered underweight with a BMI of 18.4. A healthy weight range for that woman would be 108 to 145 pounds.
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.