Being naturally underweight myself I want to stress the importance that people who are underweight and feeling week have to eat so that you maintain your strength. I hear so many times on this website, especially on the
Candida Support Forum people complaining of getting too skinny by following fasting protocols and extreme diets such as low-carb, raw food, etc. I have made these same mistakes and tried all different diets and have made myself MUCH worse while experimenting with these. The main problem is that your digestive system is not functioning properly. When you eat anything, especially sugars and simple carbohydrates you feel sick because your system cannot properly assimilate nutrients and expel waste (also feed candida, parasites, etc.). When you eat less food, do any type of fast, or follow low-carb diets you will feel better. Why? Because there is less stuff to accumulate in the intestines and cause further problems, less stuff to feed the bad guys (and also less stuff to feed YOU, by the way!). So we feel better and say, cool I found a diet or protocol that makes me feel better. For people that are overweight or healthy weight these diets may not cause too many problems (although eventually they could also have problems) but for underweight people, this will cause you to loose weight and your body will start to become weaker (sometimes it can take a while before you realize what is happening). Long-term, even though a certain diet may cause temporary relief of your symptoms, you will start to feel worse and worse. As your body becomes weaker, loses fat and muscle your body will also have more and more difficulty making new blood cells, bone marrow and other essentials. Your immune system will not function properly, your digestive system will become even worse. That is why when switching back to a more balanced diet it can feel like you have gotten WORSE and in fact this is true your digestive system has gotten weaker. If whatever you are doing is helping you to get more healthy, then you should have LESS of a reaction to problem foods. If you have more and more severe reactions to certain foods it means your health is getting worse.
I have personally experienced all of this and it took me a few years to really understand what was happening. Studying ayurveda really helped me to understand this concept, how the body works so hard to build up all the essential compounds and structures of the body and how easily it is all broken down when we don't give it the proper nutrition. I have read so many posts of people that are so obviously experiencing the same thing. So what is the solution? Well I can't tell you that exactly, but what I will say is that you have to follow a diet that makes you stronger. You have to be active and physically strong. Maybe you say you have too much fatigue to even do any activity, I have been there myself and I don't know what the solution is. What I will say is this: We are animals and if we were an animal in the wild instead of nested in our comfortable little offices and houses, if you don't have enough energy to be active you would have already been a dead animal long ago. What I mean is all animals either have to be in amazing physical shape to hunt for food or they have to be in amazing physical shape so that they can escape being food for another animal. That is why you will never see an out-of-shape animal. If an animal becomes unhealthy it will die very quickly, unlike humans who can be as good as dead for many, many years and suffer their whole lives (so depressing but if we look around we see it everywhere). We all should be able to sprint very fast at our top speed and not get injured. Any human that cannot do this is unhealthy and will lead toward physical suffering.
I used to exercise and be in good shape (but I was also doing a lot of things wrong at that time also) and then after following raw diets and fasting I slowly became weaker and weaker and stopped being active and before I realized what had happened, when I finally decided to try to be more active, I was way too weak, could not run at all and it took me such a long time to improve. Even now I am still not as strong as I was 6 years ago. Well I know I'm not offering any solutions exactly, I have made a lot of progress since feeding myself a good amount of the proper food. When I started this whole healing process I was a complete mess, then I made things even worse, and now I am finally pretty much healthy (aside from getting malaria about 5 months ago). My goal is to become healthy to the level of animals living in the wild, this is a very hefty goal as I would imagine less that 1% of people on the planet are at this level of health. When I reach that goal I will tell you how I did it. On a side note, I have met people that are completely physically inactive that keep themselves healthy only through meditation and breathing exercises but I think this is extremely rare.