Why Is Being Underweight Bad?

In this day and age, everyone is trying to lose weight. Being overweight is something that is all too common and that has many negative effects on our body increasing our blood pressure, placing strain on our heart, increasing the chances of developing diabetes and placing a lot of extra weight on the joints. For many people it also looks unattractive and will stand in the way of your success in business and relationships and can also leave you out of breath and less mobile.

So it makes sense to want to lose weight, and this is why many people are trying every day to do just that. The complication arises however when someone loses too much weight and end up too thin. Everyone will become concerned about someone who is underweight and after being encouraged to lose the weight suddenly no one will seem to be behind them any more. So why the sudden turn around and why is being underweight a bad thing too? Here we will look at a list of reasons why it’s important to keep some meat on your bones, and why people will be concerned if you take the weight loss too far. Heed the warnings below and as in all things seek the ‘middle way’ to maintain a balanced diet and weight.


When we eat more calories than we use our body stores this as fat. Of course though, like most of the body’s behaviour this is something that we have evolved, and this means that it has been found throughout our development to be beneficial for our health and survival. We store fat for a reason and so to avoid storing it at all is folly and working against your body rather than with it.

The reason that storing fat is useful is that it means we have a back up store of energy and the body can then burn those fat cells in order to release the glucose and ATP we need to perform our bodily functions. Someone who is underweight will not have this fat to burn and so they will quickly run out of energy. This is more serious than you might think as in order to keep going the body will then ‘cannibalise’ itself and burn other tissue for fuel such as muscle mass. This then means that an underweight person is likely to have a low skeletal muscle as it will be constantly burned for energy. This weakness will then mean they are unable to perform basic tasks and will also leave them more prone to accident and injury (muscles help to keep us balanced and also add a protective layer to defend against impacts).

You might think that you don’t need these extra stores of energy if you’re not planning on going running at all or doing any other marathon endurance events. However this is ignoring the fact that the body needs energy to perform all its normal tasks and even when you’re sleeping or motionless the body will burn fat stores in order to give it energy to maintain your immune system, or to make repairs and heal wounds etc. If your body doesn’t have the energy to perform these tasks however then this will leave your body vulnerable with a weaker immune system and will mean that wounds heal more slowly and you are slower to recover from illness as well as more vulnerable to getting ill in the first place.


Having a very low bodyweight will make you low in energy as discussed and this in turn can lead to malaise, lethargy and potentially depression. This of course is a cause for concern for any friends or family. Being underweight is also often a sign of being unhappy and we often lose weight when we are very unhappy due to loss of appetite and other effects. Thus if someone rapidly loses weight it is normal for the friends and family closest to them to become concerned.


Underweight people are of course usually underweight as a result of not eating enough. This then means that they don’t get as much fat, but it will also mean they get less of all the other things that the body needs in order to operate effectively and thus there is a good chance that underweight individuals will be malnutritioned unless they have supplemented well and comprehensively.

This then results in many other problems for those who aren’t getting enough food. For instance a lack of fats will result in the skin and hair drying up and flaking/thinning. A lack of protein would also contribute to this and mean the body didn’t have enough amino acids to maintain healthy skin, hair and nails or to build muscle and repair wounds. Low amounts of vitamins and minerals meanwhile would further cause bad skin and health, as well as leading to weak bones and a high chance of osteoporosis (due to low calcium), cramping and a poor immune system and regular illness.


People who have once been overweight will often strive to lose more weight than they in fact should. Despite the image promoted by size zero models and much of the media, most people do not actually find a complete lack of fat attractive as it leaves the person looking bony and having no shape or curves. A girl who loses all of her weight will lose her breasts which are made mostly of fat and will lose the shape of her buttocks and her hip-to-weight ratio. A man losing the same amount of weight could end up looking very thin and so much weaker and unable to protect and provide for a partner. This is then compounded by the malnutritioned look that consists of thin hair and damaged skin.


If women lose too much weight this can interrupt their biological clock and their menstrual cycle. In turn this can then lead to irregular periods and eventually mean that they stop having periods altogether. In most cases gaining weight again will mean that their fertility returns, but in some cases they can permanently lose the ability to have children.


If you have lost a lot of weight rapidly this can be a sign of anorexia. At the same time it can also lead to your losing more weight more quickly as you get hooked on the results that you are getting from dieting. Anorexia is very bad for you as it causes you to lose your own self-image and this means you believe yourself to be overweight when you are in fact underweight and you will lose even more weight to the point where it becomes highly dangerous and the body has barely enough nutrition or energy to run. Extreme weight loss can eventually be fatal and this is a real concern for those with anorexia.

Comments 4
  1. This article is amazing, I sent it to my friend who's starving herself, if nothing else she's feeling awful and hopefully reconsidering.

  2. In regards to the statement "Underweight people are of course underweight as a result of not eating enough"——-I take with a bit of offense.

    I am a 54 year old female who has a long history of stomach, intestinal, and digestive problems. (At 23, 1/3 of my stomach was removed, as well as scar tissue, and some 6 inches of small intestine.)

    I have been in and out of the hospital over the years for hypermesis, dehydration, etc, the last time being 3 weeks ago.

    I am 5'2", weigh 85 pounds, and have a BMI of 15.55. My blood pressure tends to be on the extremely low side also (average is 70/40). I tire very easily and quickly, have trouble concentrating, and do not sleep very well.

    The reason I take offense at that statement above, is that I eat ALL THE TIME! I'm a 'grazer'. I'll have 2-3 bites of food, then am stuffed. Within 25 minutes of eating, I am throwing up what I just ate.

    My question is this: How can it be said that I don't eat enough and that's why I am underweight?


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