You can become sick for a variety of causes, including any bacterial or viral infection or any medical problem. When you are sick, it's a typical observation that you drop a few pounds, but the cause of this is never entirely understood. People speculate that it might be caused by illness, but what actually transpires during illness that results in weight loss? Here, we will discuss why you lose weight when you become sick. Why Do You Lose Weight When Sick? When you're sick, your body goes through various changes that include appetite loss, nausea, a feeling of coldness, shivering, and even weight loss. Let's examine the reasons why you lose weight while you are sick. You lose weight when you are sick due to: 1: Loss Of Appetite The first sign you face when you are sick is that you lose your appetite because your stomach feels that it can not handle much food in it and even thinking of having something to eat makes you nauseous. This loss of appetite will make you eat very little food which will automatically result in a drop in body fat because the body will use the stored fat to provide energy and fight the infection. 2: You Become Calorie Deficit When you become sick, you don’t feel like eating and whatever you eat is lost from the body through vomiting or diarrhea. When you are not eating enough food it means you are taking fewer calories than your body’s requirement, and the calories you eat are also lost from the body which makes you in a calorie deficit state. 3: Diarrhea And Vomiting When you are sick, you mostly feel nauseous and get vomiting and diarrhea which causes a lot of fluid loss from your body. In this condition, it is always challenging to maintain fluid and food in your body because whatever you eat or drink just gets out of the body through vomiting or diarrhea. This fluid loss from the body changes fluid volume and makes you lose some pounds temporarily. 4: Loss of Water Weight Due To Dehydration The weight that is lost due to sickness is not the actual fat but the water weight due to the loss of liquids and fluids from the body that causes fluid imbalance. When you are ill, you have more urine leading to dehydration. The fever you get when you are sick makes the body produce more sweat to cool down the temperature which also causes fluid loss from the body and causes dehydration. Moreover, water is also lost in vomiting and diarrhea all of which result in loss of water weight. 5: Loss of Energy Due To Fatigue When you are sick, your body and muscles are under fatigue as they are fighting off the infection by producing antibodies. In this way, there is no or very little energy left for the burning of calories, so the body uses the stored fat, which results in a drop in weight. The loss of energy also makes you eat less because there is not enough energy left for the digestion of food. How Much Weight Do You Lose When Sick? The intensity and length of your sickness or illness will determine how much weight you will lose. You will only lose a few pounds if you have a moderate illness like the seasonal flu or a cough, but if you have a severe sickness like a viral or bacterial infection, you may lose a few more. Additionally, your present body weight and the indications and symptoms of your sickness must be taken into consideration. For instance, if you experience more vomiting or diarrhea or are unable to eat, you will lose more weight. Conclusion When you are sick due to any reason, you lose weight because of changes occurring in your body that cause loss of appetite, make your calories deficient, cause loss of fluid due to vomiting and diarrhea, loss of water weight, dehydration, and loss of energy due to fatigue. All these factors contribute equally to making you lose weight in sickness.

Why Do I Lose Weight When Sick?

Being sick makes several changes to our body. As you may have observed when you are sick you feel less active and less energetic. Sometimes the sickness may be a timely illness that leaves a little impact on your health which can be recovered in a day or two. One of its impacts is weight loss, such as losing a few lbs in case of timely illness or if you have any chronic disease, it might be eating up your body for a long time and you end up having excessive weight loss. 

Why do I lose weight when sick?

Losing weight when sick isn’t something serious if there is a slight change it might be the water/fluid weight that is lost and can be regained in a day or two but in the case of adverse weight loss, there can be a serious medical condition behind it, and has to be addressed promptly. 

Losing weight when sick can be due to the following reasons:

  1. Anorexia (Loss of appetite)
  2. Increase in metabolism
  3. Muscles loss
  4. Stress
  5. Gastrointestinal issues

1: Anorexia (Loss of appetite)

You may have noticed you don’t feel hungry when you are sick due to Anorexia (lack of appetite). Anorexia is one of the most common symptoms when you are sick and you stop eating anything. This is because of the cytokines that your body produces while fighting against the viruses and bacteria that cause the disease. Even if you try eating forcefully it doesn’t seem effective; hence due to low-calorie intake, you shed weight. 

2: Increase in metabolism 

When you are sick your body develops a combat mechanism against the bacteria and viruses which heats up your body and causes the metabolism to speed up. Due to the speed-up metabolism, the calories tend to burn faster, resulting in weight loss.   

3: Muscle loss

One of the reasons behind weight loss is the shrinking or thinning of muscle. Due to being inactive while you are sick, you tend to lose some muscles. Similarly, the body breaks down the tissue cells to gain energy which causes excessive weight loss. 

Sometimes chronic conditions can lead to excessive Muscle loss, in such a situation professional help is advised to know the underlying cause. 

4: Stress

People often stress about being sick even if the illness is not too serious and get depressed, not knowing that stress and depression are the ultimate cause behind all diseases. Therefore due to excessive stress and staying depressed, you lose weight. 

5: Gastrointestinal issues:

Being sick may cause digestion and gastrointestinal issues which make your stomach vulnerable to everything you eat and can result in diarrhea and vomiting leaving your body dehydrated. Therefore due to excessive dehydration, people tend to lose weight which is generally fluid/water weight.

How can I feel better?

Certain precautions are to be taken in order to cope with your sickness, this isn’t anything hard to achieve it just needs a little dedication and effort. To make yourself feel better you can also try the following ways:

  1. Relax
  2. Balance Diet
  3. Exercise
  4. Medication

1: Relax

You can opt for activities to relax and make yourself feel better, sometimes lying in bed is not the only option we can have. You can always do the things that work for you in making you feel better even when you are sick. 

For instance; you may take a hot bath or have a body massage to relax. 

2: Balance diet

A good healthy diet is the major component for those who want to step out of their illness. If you still don’t feel like eating anything start with food that is high in nutrients such as soup, vegetables, meat, fish, and fruits. Consuming such food will help your body to regain its energy. 

3: Exercise

You may go for a walk near your area to get in some fresh air which soothes your illness and relaxes your mind. 

Having a little movement in your body will make you feel better by reducing stress, increasing blood flow, improving digestion helping you fight against your sickness. 

4: Medication 

Take proper medication as advised by your doctor. Along with the medications follow all the necessary guidelines your doctor advises you to ensure a speedy recovery.

Note that it is mandatory to take medications as per the doctor’s advice. Taking medicine on personal suggestion can make your condition worse and can lead to many adverse effects like nausea, diarrhea, headache, and dizziness.

Note: If you continue to lose weight over time for unknown reasons you should contact a doctor and discuss your symptoms in order to identify the main cause. 


It has been observed that people tend to lose weight when they are sick, this happens due to various reasons. When you are sick your body develops a combat mechanism to fight against the bacteria and viruses which often leads to fatigue, energy loss, and even weight loss.  This weight you lose is not something to get worried about it is mainly the water or fluid weight that can be regained in a day or two of proper care, to make yourself feel better while fighting against an illness you must take proper rest, munch on a balanced diet, have a little exercise and take proper medication as advised by your doctor


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