Word of advice: don't take dietary advice from fat people. Whatever advice they're giving you is rubbish obviously as - hello - they are still fat!
Fat people also think they're experts on losing weight. This will generally annoy the hell out of ordinary people who have put on a few pounds and are sensibly cutting back a bit in order to stop those few pounds becoming a permanent fixture. The Fat People will tell you you're doing it wrong.
Even worse are the Deliberately Undermining Fat People. If you have some of these in your life - well, you have my commiserations. They don't want to be the only fat person around so if they can grind you down long enough they reason, you might eat all the chocolate biscuits they so helpfully brought over and stashed in your cupboard.
My advice is to try and ignore these people especially if they are related to you 'in-law'. No good will come from you yelling "Shut the fuck up you fat bitch!" while your significant other tries to manhandle you out of the room. Trust me I know.
So my advice? Have veg/salad and protein with every meal and drink alot of water. Eat what you want, stop when you're full.
Or just take a look at the slim people you know and do what they do.
P.S. You may have gathered that I have 'in-law' issues.