Life has never claimed to be fair. But, as others have said, there's always more going on than what we see.
I've got these two friends. One who is larger, my size, but 5'2". The other who is maybe 135 at 5'8". The skinnier friend said to the larger (during a discussion, so it wasn't rude or anything) "I don't know why you'd be larger than me, you eat the same that I do!"
But that wasn't true... in front of the skinnier friend, my larger friend ate the same, then when the larger friend came home to eat a meal alone she ate A LOT more. Or she had snacks or things. With the skinnier friend, she didn't go home and do that. I'm not saying it's the same way with you or everyone, just that often our perceptions deceive us because we aren't getting the whole story.
I used to be SO self-conscious of what I ate in front of skinnier people. ("Oh gosh, are they thinking about what I'm eating... I better eat less than them.") But, on my own (yes... secret binge eater here) I'd watch TV and become a bottomless pit. Heck, they may have been surprised at how I could gain this weight, but I wasn't.
As a side note, I've gotten much better about just enjoying what I want to eat in front of others. I don't feel bad about eating until I'm satisfied in front of those who are (at the moment

) skinnier than I am. Working on this has kept me from secretly eating later. In fact, I haven't secretly eaten in a long time, thanks to all the healthier changes I've been making...
Oops, anyway </side note>.
