Understanding the Dangers of Being Underweight: Determining a Dangerous BMI

Body Mass Index (BMI) is a widely used tool to assess an individual’s weight status and overall health. While it is important to maintain a healthy weight, it is equally crucial to recognize when someone is dangerously underweight. In this article, we will explore the concept of being underweight and discuss the BMI range that indicates potential health risks associated with low body weight.

Understanding Underweight:

Being underweight refers to having a body weight that is lower than the average weight range considered healthy for a person’s height, age, and gender. It is important to note that being underweight can have detrimental effects on an individual’s overall health and well-being.

Determining a Dangerous BMI:

BMI is calculated by dividing a person’s weight in kilograms by the square of their height in meters. The World Health Organization (WHO) has established different BMI categories, including underweight, normal weight, overweight, and obese. However, it is essential to remember that BMI alone may not provide a comprehensive assessment of an individual’s health status.

To identify a dangerously underweight BMI range, we need to consider the specific cutoff points established by the WHO. According to their guidelines, a BMI below 18.5 is considered underweight. However, it is important to remember that this range may vary depending on a person’s individual circumstances, such as muscle mass, bone density, and overall health.

Health Risks of Being Dangerously Underweight:

Being dangerously underweight can lead to several health complications, including:

1. Nutritional deficiencies: Inadequate caloric intake often results in a lack of essential nutrients, vitamins, and minerals, which can impair various bodily functions.

2. Weakened immune system: Underweight individuals may have compromised immune systems, making them more susceptible to infections and illnesses.

3. Decreased muscle mass: Insufficient calorie intake can lead to muscle wasting, weakness, and a decrease in physical strength.

4. Hormonal imbalances: Being underweight can disrupt hormonal balance, leading to irregular menstrual cycles in females and decreased testosterone levels in males.

5. Osteoporosis: Inadequate nutrient intake can weaken bones, increasing the risk of fractures and osteoporosis.

6. Impaired organ function: Insufficient body fat can negatively impact organ function, including the heart, liver, and reproductive organs.

Seeking Professional Guidance:

If you believe you or someone you know is dangerously underweight, it is crucial to seek professional help. Consulting with healthcare professionals, such as doctors, nutritionists, or dietitians, can provide personalized guidance and support to help restore a healthy weight and address any underlying health concerns.


Maintaining a healthy weight is essential for overall well-being, and being dangerously underweight can have severe health implications. While the BMI cutoff point for underweight is below 18.5, it is important to consider individual circumstances and consult with healthcare professionals to determine the best course of action. Remember, seeking guidance and support from experts is crucial to address any potential risks and promote a healthy lifestyle.