BMI 16 to 18.4 is Underweight

A BMI of 18 can indicate that your weight is low. Low body mass can decrease your body's immune system, which could lead to illness such as malnutrition, bone loss, and other conditions. The lower your BMI the greater these risks become.


With a BMI of , your body weight is considered too low to be healthy.

A person may be underweight due to metabolism, lack of food, genetics, or illness.

Being underweight is associated with certain medical conditions, including hyperthyroidism, cancer, or tuberculosis. People with gastrointestinal or liver problems may be unable to absorb nutrients adequately.

The underweight may additionally develop hair loss or osteoporosis, even if they are quite young.

If your body doesn't have enough fat and nutrient stores, you might feel weak. This lack of energy may make it difficult to get through day-to-day tasks at work, home or school.

Lack of energy is likely due to a lack of iron in your blood, a nutrient that helps prevent anemia.

Although being underweight has been reported to increase mortality at rates comparable to that seen in morbidly obese people, the effect is much less drastic when restricted to non-smokers with no history of disease, suggesting that smoking and disease-related weight loss are the leading causes of the observed effect.

Underweight treatment

In order to gain weight, you will have to eat more calories.

The best way to add weight is to increase your intake of complex carbohydrates, particularly whole grain ones. Foods like whole wheat bread, muffins, pasta, crackers, Noodles, and bagels are good to include. Also, legumes and fruits would be wise choices.

You will need to include regular exercise and strength training into your lifestyle in order to prevent gaining too much weight as fat. And, as I mentioned, those extra calories should come mainly from additional carbohydrate.

It is best to gain weight slowly and steadily. This will help to ensure that your weight gain is in the form of lean body mass and not excessive fat.

Tips to gain weight

  • Drink 6 glasses of water a day.
  • Eat lots of raw fruits and vegetables (green leafy vegetables are great)
  • Do not drink coffee, or alcohol.
  • Do not eat processed foods (sugar, white flower, ...)
  • Keep track of everything you eat.
  • Avoid red meat and animal fats.
  • Eat frequent but small meals.
  • Reduce intake of dairy products.
  • Do not smoke.

A qualified nutritionist will try to help you gain weight safely, and once you have reached your goal will help you to ensure you eat the right amount of food to meet your needs but also to be in balance and remain within a healthy weight range.

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