What are the BMI risk categories?

Keith Kreitz, MD
Bariatric Medicine
A healthy body mass index (BMI) risk category is 18.5 to 24.9. When people get to a BMI of 25 to 29.9, they are considered overweight. A BMI of 30 and above is in the obese category, with 35 and above being degrees of obesity.  Forty and above is extreme, or morbid, obesity. People with a BMI of 35 to 39.9 and medical problems, and all people with a BMI of 40 or more have a higher risk of health problems and death.

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Today, healthcare providers use a measure called BMI, short for body mass index. This gives a good measure of your total body fat. BMI compares your height and weight. It shows if you are underweight, at a healthy weight, or overweight.
  • Below 18.5 -- Underweight
  • Between 18.5 - 24.9 -- Healthy weight
  • Between 25 - 29.9 -- Overweight
  • Over 30 -- Obese
The World Health Organization and the National Institutes of Health define normal weight as a body mass index (BMI) of 18.5-24.9, overweight as BMI of 25-29.9 and obesity as a BMI greater than 30. Obesity is further categorized as class I (30-34.9); Class II (35-39.9) and Class III (>40).
To find out your BMI, divide your weight in pounds by your height in inches multiplied by your height in inches. Take that number and multiply it by 703.
A BMI of less than 18.5 is considered “underweight.” A BMI between 18.5 and 24.9 is considered “normal weight.” A BMI of 25 to 29.9 is considered “overweight.” A BMI of 30 or greater is considered “obese.”
Morbid obesity is defined as having a body mass index (BMI) of more than 40. For men that equates to approximately 100 pounds overweight for women, 80 pounds overweight.
Marjorie Nolan Cohn
Nutrition & Dietetics

Overweight and obesity are both labels for ranges of weight that are greater than what is generally considered healthy for a person’s height. The terms overweight and obese also identify ranges of weight that have been shown to increase the likelihood of certain diseases and other health problems.

Obesity is a state of excess adipose tissue mass, or body fat. This condition usually translates into excessive body weight. On the one hand obesity can develop even in the absence of excessive body weight, whereas on the other hand a person (e.g., a body builder) can develop remarkable overweight without excessive body fatness. Meaning, ‘slim’ people can have a high fat mass and ‘overweight’ people (for their height) can have low fat mass.

  • An adult who has a BMI between 25 and 29.9 is considered overweight.
  • An adult who has a BMI of 30 or higher is considered obese.
Body mass index (BMI) risk categories are:

Underweight: below 18
Healthy weight: 18 to 24.9
Overweight:  25 to 29.9
Obese: 30 to 39.9
Morbidly obese: 40 and higher

Body mass index (BMI) is a scientifically accepted measurement of body weight as it relates to health. While BMI is not a direct measure of excess body fat, it is the recommended method to diagnose overweight and obesity. Weight Watchers can help you reach that healthy range.

Weight Watchers offers a comprehensive approach to weight loss that can help you reach your goals.

Ideal Weight Calculator (Body Mass Index) is a reliable indicator of your body’s fitness level, and most importantly, your health risk. It works by calculating your weight and height correlates to your body fat level. To use a calculator to determine your BMI, go to:

The adult BMI risk categories are:

  • Adults with a BMI below 18.5 are conidered underweight.
  • Adults with a BMI 18.5 to 24.9 are conidered normal weight.
  • Adults with a BMI between 25 and 29.9 are considered overweight, but health practitioners consider this to be low risk since some amount of fat reserve is needed for energy. This extra energy can be helpful during severe, chronic illness or stress.
  • Adults with a BMI between 30 to 34.9 are considered obese and have a greater risk of chronic diseases like cancer, diabetes and heart attacks. You also have an increased chance of dying by 40% according to the New England Journal of Medicine.
  • Adults with a BMI above 35 are considered to be morbidly obese and have an increased chance of death by 250%! If your BMI is high, don’t let the numbers overwhelm you. The important consideration is that you’re going to take control of your health today!
Eric Beard
Sports Medicine
The Body Mass Index (BMI) risk categories are;

18.5 or less = Underweight
18.5 to 24.9 = Normal Weight
25.0 to 29.9 = Overweight
30.0 to 39.9 = Obese
40 and above = Morbidly Obese

Those individuals who score in the obese and morbidly obese categories are at risk for serious health conditions and disease such as; heart disease, stroke, type II diabetes and certain types of cancer. 
The adult BMI risk categories are:

BMI <18.5 = underweight
BMI 18.5 to 24.9 = healthy
BMI 25.0 to 29.9 = overweight
BMI >30.0 = obese
BMI >40.0 = morbidly obese.
The (adult) categories* for risk based on your BMI are: below 16.5 = severely underweight; 16.5 to 18.4 = underweight; 18.5 to 24.9 = healthy; 25 to 30 = overweight; 30.1 to 40 = obese; above 40 = morbidly obese. *BMI risk categories for children are different and are gender dependent until the age of 18.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.