How to increase the appetite? i tend to lose interest in food after being hungry for a little while..

Try eating small: Balanced healthy low fat snacks every 2-4 hrs (~150-200 kcals). Sometimes, as one eats, less, the hunger signal gets '.Lost'. I am assuming you don't have problems w your sense of smell, sinusitis, abdominal pain, nausea, etc. Also try increasing your daily exercise - e.g. A daily vigorous 30 min walk, etc, preferably outdoors. Finally, any chance you have some depression &/or anxiety going on?