Health Risks When Underweight


There are many studies on the health effects of overweight, but what about the impact of underweight? Many health risks are associated with low weight or poor nutrition. Include:

  • Malnutrition, vitamin deficiency or anemia
  • Osteoporosis due to too little vitamin D and calcium
  • Decreased immune function
  • Increased risk of surgical complications
  • Reproductive problems caused by irregular menstrual cycles
  • Growth and development issues, especially in children and adolescents

Read on to find out more about the risks of underweight, plus how to identify if you are underweight, the symptoms you encounter and how you find help.

Body mass index (BMI) helps you and your doctor determine if you are underweight. BMI is an estimate of your body fat based on your height and weight.

BMI range Weight status

  • Less than 18.5 – Underweight
  • 18.5 – 24.9 – Normally
  • 25 – 29.9   –  Overweight
  • 30 or more – Obesity
  • Athletes have muscles. Because muscles are more massive than fat, BMI appreciates body fat for these people.
  • Older people lose muscle. In this case, BMI underestimates body fat.



If you are underweight, you do not eat enough healthy foods with essential nutrients to supply your body with energy. That causes malnutrition. Over time, nutrition affects your health in different ways.

Symptoms include:

  • Feeling tired or running out of energy
  • Suffer from frequent illness or difficulty in fighting disease
  • Have problems with thinning or losing hair, dry skin or dental problems

A study from Japan compared the dietary habits of underweight women with the desire to lean compared to underweight women without this desire. They found that underweight women with less desire to eat have less healthy eating habits than underweight women without this desire.

If you are underweight, you may be malnourished if your BMI is low due to an unbalanced diet or an underlying disease that affects nutrient absorption. Malnutrition also leads to anemia or an essential vitamin deficiency. Anemia is caused by poor absorption of nutrients.

Reduce Immune Function

A recent review of studies has found an association between increased infection and underweight. Researchers note that they have difficulty determining whether this is the result of a lack of weight or a variety of underlying causes of underweight. For example, malnutrition leads to reduced immune function and also causes people to be underweight. More research is needed to understand the link between weight and immune function fully.

Increased Risk of Surgical Complications


One study found evidence that underweight people who had knee replacement surgery were more likely to develop postoperative infections than those without weight loss. Although they cannot determine the reason for this, they believe that underweight people cannot heal wounds as well as those with healthy BMI. They also found that the underweight group had a low preoperative hemoglobin level. Although more research is needed, the findings suggest that underweight affects your ability to heal wounds.

Another study showed increased complications in underweight people who had hip replacement surgery compared to those with a healthy weight. Complications after coronary artery bypass surgery and lung transplantation also seem to be higher for underweight people. Researchers have also linked low BMI with increased postoperative mortality in the first year after lower limb bypass surgery.


Low body weight increases the risk of low bone mineral density (BMD) and osteoporosis. One study looked at BMD among 1,767 premenopausal women and found that 24% of women with BMI 18.5 or less had low BMD. Only 9.4 percent of participants with a BMI higher than 18.5 had low BMD. Research results show that lack of weight increases the risk of osteoporosis.

Seek help

If you suspect you are underweight, see your doctor or dietitian. Your doctor will check your medical history and help identify any problems that lead to poor nutrition or weight loss.

From there, you can come up with a plan to help you achieve that weight through healthy eating and other appropriate treatments.

With the help of your doctor, you will achieve normal BMI through lifestyle changes and healthy eating. The doctor also helps you navigate solutions to limit access to nutrient-dense foods, psychological problems, potential health conditions, medication side effects. And other situations that lead to lack of weight or malnutrition.


Under Weight

By making some adjustments in your diet and lifestyle, it will help you gain healthy weight and avoid the adverse health effects of underweight.

  • Try eating smaller and more frequent meals. Add more snacks to your routine as well.
  • Stick with nutritious foods, such as cereals, fruits, vegetables, dairy products, nuts, and lean proteins.
  • Pay more attention to what you drink. Smoothie is a better choice than diet soda, coffee, and other drinks. You will add substances with fruits, vegetables, and dairy products.
  • If drinks reduce your appetite, consider drinking them after you’ve eaten.
    Get more calories in your meals by adding foods like cheese, nuts, and making toppings to the main dishes.
  • Starting exercise will make you gain weight by adding muscle to your body. Exercise will help stimulate your appetite.

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About the Author: Maria Gattuso

Hi There. I'm Maria Gattuso I hope that the community of Beauty Health - Fitness lovers will always support and let accompany you in the long path of health training, or find the perfect version for your own body.

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