After reading your question, I would have him see his doctor for a full blood work up. Being tired as you describe, can be due to blood sugars, his thyroid, anemic. Some can even develop food allergies (which is more on the rare side) Electrolyte imbalance and even possible CFS (Chronic fatigue syndrome) So do start with a full blood work up, which majority of the things listed above can be detected via the blood work and give his doctor a clearer picture of what is going on.
Best of luck Hun, Hope this helps, If you need anything else please feel free to ask. If you found this helpful don’t forget to click the *Accept* button.