Underweight: what are the causes, symptoms and solutions?

Body Mass Index
Body Mass Index

The average Dutch person would be only too happy to weigh a little less. But being underweight is at least as big a problem as being overweight. The causes can be both physical and psychological in nature. Those who really weigh too little run the risk of all kinds of small and large health problems. Fortunately, there are plenty of solutions to get back in balance with your body. Sometimes a few eating tips are enough, in other cases intense psychological support is necessary. Discover the causes, symptoms and solutions of being underweight.

What is underweight?

Underweight can be determined numerically with the BMI index. Divide your weight in kilograms by the square of your height in meters. Based on this, you have an idea to which category you belong. A BMI between 18.5 and 25 is normal. People over 25 are overweight. As soon as your BMI falls below 18.5, we speak of underweight, whereby we can make additional subdivisions:

  • > 30: serious overweight
  • 18.5 – 25: normal weight
  • <18.5: underweight

Although the BMI is used as a measure, this index has many limitations. That is why it is important to interpret the index correctly. If your BMI is just too low (eg 18), but you eat regularly and healthy and you feel fantastic, then there may be little to worry about. For example, it could be a genetic predisposition.

When your BMI does reach a value of 18.5, but you have all kinds of intestinal complaints or you avoid food because you want to meet an unrealistic ideal of beauty, then it is time to seek help.

What are the causes of being underweight? 

Being underweight can have both physical and psychological causes. It is important to gain a good insight into what the real cause is, only in this way can the right solution be found. If you are not sure what is going on, consult a specialist. We discuss the main causes:

A high metabolism

A high resting metabolism or basic metabolism means that your body uses more energy at rest than someone else of the same weight. This could be genetic, or there may be something wrong with your thyroid. The thyroid gland determines how much energy is produced in your body. For example, it may be that your thyroid gland is overactive, causing your metabolism to run very fast.

Physical disorders

There are several conditions that can have a major effect on your weight. For example, in the case of stomach or intestinal complaints, food is no longer absorbed into the body. And in other diseases, the appetite disappears.

Some examples are stomach infections, chronic infectious diseases, chronic diarrhea, irritable bowel syndrome, AIDS, cancer, stroke or severe burns. 


Starvation is usually caused by environmental factors in the developing world. Fortunately, we have access to adequate nutrition. (Consciously starving yourself is one of the psychological causes.) 

Frequent and intense exercise

Endurance athletes who exercise for several hours a day in particular burn a lot of calories. In addition, it is an advantage for runners and cyclists to weigh less. The less weight you carry with you, the faster you are. Although these people want their body to perform optimally, this can be at the expense of health. Even though exercise is healthy in itself, those who eat too little will not get enough nutrients to stay healthy.

Mental illness

Unfortunately, in our society there is a great focus on a slim and lean body. Obesity is a major problem that needs to be addressed. But the ideal image of bone-thin models is not the solution. Especially in young girls (but increasingly also in boys) this leads to psychological disorders, including the eating disorder anorexia nervosa. The actual nature and origin of this disease is much more complex. Therefore, do not hesitate to ask for help, better too early than too late. 

What are the symptoms and consequences of being underweight? 

Who, for whatever reason, gets too few nutrients and loses too much weight will no longer feel healthy and vital. In the first place, you feel tired and listless and your energy and fitness deteriorate. You may also suffer from dizziness and depressed feelings. 

In the beginning, your body will try to survive by using your energy reserves and burning fats. But after a while, the fat stock will also decrease and you will also be deficient in many nutrients such as vitamins and minerals.

Slowly but surely, all processes in your body are hindered by this. The organs are affected and their condition deteriorates. In severe cases, it can also kill you. 

Some typical consequences of being underweight are: 

  • Low energy & constantly tired
  • Skin, hair and dental problems
  • Low libido
  • Sleep problems
  • Osteoporosis
  • palpitations
  • Difficult digestion
  • Swollen hands and feet
  • Down hair on your body and in your face
  • Anemia
  • Getting sick regularly
  • Irregular or cessation of menstruation (amenorrhea)
  • preterm birth

What is the best treatment for obesity? 3 possible solutions

Only when you know what the real cause of your underweight is, you can choose the right solution. Be open and honest about this and try to find someone you can talk to: friends, family, a nutrition coach, a doctor or a psychologist. There are 3 important pillars in the treatment of underweight: your health, a nutrition plan and your mental well-being.

1. Restore your health

If you have health problems, you should always address them as soon as possible. Those who have intestinal problems and therefore absorb no or too few nutrients will not find any improvement by eating more. First you have to get your health in order. Consult a nutrition coach or other health professional for this.

In the case of a serious illness such as cancer, this is of course a more difficult problem. In this case, a whole team of professionals will have to look at how the problem can be tackled. 

2. Use a nutrition plan

If you are underweight because you simply eat too little in relation to your consumption, a nutrition plan is usually sufficient to get you back on track. With a FitChef Premium subscription you get a weekly eating schedule with healthy recipes in which the amount of calories is perfectly tailored to your personal needs. By following this for a while you will slowly but surely gain weight again. 

3. Consult a (nutrition) psychologist

In many cases, eating problems are just an expression of underlying psychological issues. There’s no point in pushing someone who doesn’t eat because of low self-esteem or depression to eat more. The root of the problem is mental and therefore the right solution is psychological help.

For minor problems, a nutrition coach can offer help. But in most cases, a nutrition psychologist will be a better choice. Asking for help is not a sign of weakness, but of courage!

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