Cancer treatment may not leave you with a huge craving for food, but you have to eat right, still. It has never been more important for you to eat the right foods and avoid the wrong ones. Your body is working really hard to overcome the cancerous cells, and it needs all the nutrition and help it can get from your side.
Most people think that it would be better for them to have multi- vitamins in order to gain their strength, but that will not help. You should certainly stay away from protein and vitamin pills if you are undergoing cancer treatment. You should focus on getting your nutrition directly from food. It’s best for you to eat whatever you feel like eating- just make sure you are not junk eating, or eating processed food. Fresh foods are the ones that would suit you body the best. In case your stomach does not agree with the food you are eating, you should try integrating some cold foods into your diet. Eggs, beans, milk, cheese, meat, fish, etc. are incredibly good for your body during this period.
You should not ignore your fluid intake during this period, either. You may not feel like drinking water (patients undergoing chemotherapy find the taste of water strange, sometimes). If that is the case, you could try drinking nutritional drinks, if the taste agrees with you. You could also try getting your liquid requirements in the soup form.
As of fitness, do not resort to any strenuous physical activity without getting the express permission of your physician. Whether you are allowed to workout, or even walk, depends on your personal condition and only your physician will be able to determine how much you can exert yourself physically without it becoming a problem.