The opposite of ''diet''.

Hello,

I hear people say; I want to slim down, I want to get back in shape, I want to lose some kilos,…

All those would give the same meaning of ‘‘diet’’.

If someone wants to do the opposite … then what the proper word to use for such a dietary? Something other than ‘‘to gain weight’’. Even if it’s funny to say. I’d like to learn some…

Hello,

I’m not very good in English but I have heard expression - ‘to put on’ weight which means to gain a few kilos.
e.g. from Internet
* I must go on a diet, I’ve put five kilos on since the holidays.
* He was looking a little fatter. I think he has put some weight on.

I’ll be happy if you find it useful.

Kind Regards, Loretta

Thank you Lorensita.

I’ve read about ‘‘fatten me up’’, too.