Interesting thread. There's been lots of talk of metabolism and fat people blaming a slow metabolism and vice versa. That's been extensively debunked? www.nhs.uk/Livewell/loseweight/Pages/how-can-I-speed-up-my-metabolism.aspx
There is other research which I can't find that shows slim people overestimate how much they actually eat (oh I eat loads) and fat people underestimate how much they eat (I eat hardly anything).
My DH is in the latter camp and seems to think alcohol doesn't have any calories, nor leftovers from kids plates, or anything eaten straight from the fridge. The food he eats off a plate is all he counts in his head. He needs to lose 2 stone.
I'm a size 12/10 but before marriage and kids was an 8/6. People were always saying to me how come I was so slim when I was eating a fried breakfast in the work restaurant. But I'd only have a fried breakfast on a Friday and then it'd be small, not everyday. I'd eat a proper hot lunch too. But I didn't then have another meal in the evening, perhaps a sandwich or toast. Plus I went to the gym at least 3 times a week.
I've gained weight because I eat too much. My portion sizes have increased since I've been making family meals and buying crisps, biscuits and snacks. And the peri menopausal years don't help.
From memory, you only need to add something like 2 digestive biscuits daily to your diet to gain half a stone in a year if you don't increase your energy levels.
My car was recently in the garage and in a 48 hour period I walked 11 miles which was a real eye opener.
I've begun cutting down on food and snacks as I hate this weight gain that's crept up.