Hi and welcome to HCM.
Thanks for posting your query here.
If the Tuberculosis
bacilli affect the spine it is called Pott's spine. The main line of treatment is ATT.
Most of the TB drugs will cause loss of appetite. Along the patients may experience nausea
too. Hence before hand the doctors has prescribed the appetite tonic to your father.
And the age factor also determines the digestive capacity too. Hence please give easily digestive foods like milk, bread, fruits and cooked vegetables. In the diet if you add some sort of soups with a pinch of pepper it will improve the digestive capacity.
Look for any mouth ulcers or redding of tongue. If it is so some multivitamins can help.
The ATT treatment can be faced if the patient can improve his calorie capacity.
Check his sugar levels. If they are satisfactory you no need to worry. The appetite will come back to normal. Untill then take care of his diet. Give nutritious and easily digestive foods.
Please dont worry, your father will recover soon.
Hope this is helpful to you