@ALW88,
I have battled my weight, on and off, for over 35 years. It never gets easier and, in fact, it gets harder as you get older.
So trying to lose now (sensibly, slowly) makes sense. You are far more likely to be successful and you have the chance to develop good habits and stick to them. That means not just eating better, but also getting enough exercise.
That's the good news.
The not so great news is that I know fully well what it's like when someone tells you to lose weight (or drops hints to do so) not because they care so much about you but because it is a measure of control.
I well recall a boyfriend, back in I want to say this was 1981. It was about this time of the year and it was a warm day. We lay on towels on the grass in front of his dorm, in short sleeves, and I lifted my top enough to expose my belly because otherwise my coloring tends to resemble that of a dead mackerel. A friend of his was with us, and he was really nice and he said to me, "Wow, looks like you're already in bikini shape!" I thanked him and then my then-boyfriend said, "No, she's not. If she stands up, you'll see she has a stomach."
How lovely. I broke up with him not too long after that (and no, I didn't try to date his friend). That was over 35 years ago yet I remember it stinging now (and I am a lot larger now) as it did then. It wasn't for health that that boyfriend wanted me to lose weight; it was so I would look more like a trophy.
So assess what's going on. There is no reason why your motivation has to be anything noble. Whether it's for your health or for a size 6, if you are overweight (and I don't even know if you really are, BTW), then losing a few pounds will give you a health benefit. Just because you lose weight to look better in short-shorts doesn't mean your health does not improve.
And I can see where working at a fast food place would make it harder. Still, you don't have to eat there, right? You can bring a lunch (if any workplace has a refrigerator, they sure as hell do) and also eat a good, big breakfast before you start so that you aren't tempted to snack. And a lot of fast food places offer some better choices, such as salads or grilled sandwiches. No law says you have to have the 'special sauce' if you don't want it or the fries. And no law says you have to finish it all, or eat an 'adult' portion when you really just want a kid's size meal.
Talk to him about how it makes you feel when he does this kind of pushing. Because it is pushing; it's a bit of nagging. It doesn't mean he is necessarily wrong, but his approach could sure use a makeover.