Hello, I went through your query, yes tuberculosis infection causes significant weight loss,, but once them start you on right medication, with proper high protein diet you can increase your weight, slowly when compared to general population. You need to eat more calories, Eat frequently, atleast six times a day, Eat more fresh fruits and vegetables, milk, pulses, soybean will help you to gain weight. If your health permits add some physical activity to your daily routine,, which improves your appetite and helps to gain weight. Most important is treatment to TB,, have regular follow up with your doctor.