Pfft, you're in exactly the same boat as me.
Lately I only eat once a day as well, in the evenings.
I'm 1.95m tall and I only weigh 65kg.
But why do you want to gain weight anyway? Eating less saves a LOT of money and unless your health is deteriorating, why eat more?
If you're tired, just drink some water, that always helps.
I need some KG's...I think u do 2