Eat 2 to 3 bananas per day which adds up to 300 calories. Eat 50g of groundnut which again adds upto 300 calories. Eat 10 dates which gives u around 235 cals.drink 2 glasses of milk with 1 spoon honey. Each glass gives u aroung 150 cals. Soya beans or double beans is also a good protein source. It will give u good result if u take regularly. If you are a non-vegetarian take 1 or 2 eggs (boiled egg - 75 cal / omelet - 100 cals. 1 glass of orange juice gives u 125 cals. Yes, finally take curd for lunch regularly. In addition to ur normal diet, add these to ur diet in such a way u take atleast 1000 calories extra. In one week u can gain 1 to 1 1/2 kg. In one month u can gain 4 to 5 kg. If u r not able to consume more, take in the form of liquids to add up to ur calories.
All the best.
To gain weight, here are a few basic suggestions:
Eat well balanced meals.
Go for a walk atleast 20 minutes a day to boost appetite.
Drink two glasses of toned milk with a protein supplement daily.
Have dry fruits as healthy snacks.
Eat plenty of protein.
For more appropiate customised diet plan, consider a hand held diet programme from DesiDieter.
Protein shakes are good to gain weights . You can also go for banana shake which is a natural source of fiber . And is pretty good thing to gain weight .