Health Risks of Being Underweight


Table of Contents

Being underweight is a physical condition in which the body weight of a person goes below a certain standard. A person can be Underweight due to poor diet or some other underlying conditions. In most cases, a proper and balanced diet will bring the person's weight back up.

How to Determine Whether a Person is Underweight?

Body Mass Index or BMI is a standard index recommended by the Center for Disease Control and Prevention (CDC). BMI can be used to classify a person into normal weight, overweight, or underweight.
BMI is calculated using both the height and weight of a person. The formula for BMI is:
BMI = Weight of a Person (in kgs) / Square of Height (in meters).

Following are the standard values of BMI which determine the health condition of a person.

  • Less than 18.5: Underweight
  • 18.5 - 24.9: Normal Weight
  • 25 - 29.9: Overweight
  • Above 30: Obese


Numerous causes can lead to the condition of being underweight.

  1. Poorly Balanced Diet:
    The first and foremost cause of underweight is unbalanced diet. Every person needs a minimum amount of nutrients through their daily diet. The body needs this minimal intake regularly to perform day to day tasks. Constant deprivation of these nutrients, as well as food in general, can lead to a person being underweight.
  2. Family History:
    Family history can have an impact on a person's physique. Due to these genetic characteristics, a person can sometimes remain Underweight in spite of a healthy and balanced diet.
  3. Physical Activity:
    People who are into heavy physical activities regularly will have to get excess energy in the form of calorie-rich foods. A person who is missing out on this excess energy could develop the condition of being underweight.
  4. An Underlying Condition:
    A variety of physical illness can also lead to being underweight. Conditions like cancer or diabetes often manifest with symptoms like vomiting, Diarrhoea, or loss of appetite which in turn makes a person underweight.
  5. Mental Illness:
    Mental illnesses like depression or anxiety can lead to a poor diet which in turn results in a person being underweight. Risks Studies show that the rate of mortality is more in people who are underweight as opposed to people who are of normal weight.
  6. Drowsiness and Tiredness:
    A prolonged deficiency of necessary nutrients from the body might lead to weakness and fatigue.
  7. Frequent Illness:
    Antibodies are the prime defence mechanism for a body. Hence a weaker body that is nutrient deficient might not be as effective in fighting off illnesses as a healthy body.
  8. Anaemia:
    Anaemia is a condition generally associated with being underweight. An Anemic person will have low haemoglobin count in the blood, which generally happens due to Iron deficiency. An improper diet might be the prime reason.

Treatment and Prevention

A person suffering from the underweight condition can use a balanced diet to gain weight. Some healthy tips to increase weight are:

  • Eating calorie-dense foods which will help in weight gain.
  • Eating several small meals a day ensures proper weight gain.

In some cases, a person is underweight due to an underlying condition. The treatment then, for that condition needs to be carried out first. It is always important to seek medical help if you are unsure of a solution. A person should consult a doctor if any of the following happens:

  • Sudden and significant weight loss.
  • Sudden loss of appetite.
  • Persistent Diarrhoea, Vomiting or Nausea.


In most cases, a person is underweight due to an improper and unbalanced diet and can easily rectify it by switching to a proper and balanced diet. Majority of these cases may not require constant medical care. However, if unsure, consulting a dietitian to prepare a balanced diet along with a proper workout routine is advised.

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