I know how hard it can be to face negative co-workers when being overweight is an easy target for them. I understand the military would be even more difficult due to the demands that are placed on a person to be physically fit. Men and women can be equaliy inconsiderate of others feelings, but the problem with being in a male dominate career field is the fact that we know most men tend to have a unrealistic idea of what they believe a women should or shouldn't look like. This causes major insecurities in us, and unfortunately most of us tend to have such low self esteem that we don't do anything to demand the respect that we deserve. My advice is if someone makes a remark that you're able to hear, to confront them face to face about it. Most times, they don't realize they are being heard, and the confrontation alone embarrases them and also makes them aware of the fact that 1) you won't tolerate anyones childish ill behavior and 2) you demand respect by putting them in their place.
Many times the reason someone starts pointing out our size is due to their own psychological insecurity. It's their way of trying to raise up their own self esteem because theirs too is very low, whether they will admit it or not (This is a common act in school, but also among adults). Many times it's because they have their own flaw that they are trying to cover up by pointing out another persons.
I know this may not be the answer you are looking for, but the best way to combat a person that exhibits this behavior is to 1) confront them and show them your strengths by doing so and 2) Not allowing their words to effect you by thinking to yourself 'They too have flaws though you are choosing to be more adult about it by not exploiting them to make yourself feel better.
You also need to think to yourself (I do this too) How you have many amazing traits, and the people that can only see skin deep are shallow. Yes, you can be a knockout too, but though it is Cliché 'Beauty is within'. We can change the size that we are, we can make ourselves appear more beautiful but our hearts will determine if that outter beauty is worth anything.
So what you need to realize is You are naturally beautiful inside, You can always make yourself Beautiful on the outside, but for those smucks that may be negative towards you, Their inner beauty is deeply flawed, though their outter beauty may be okay, they are seriously without.
You need to realize this, so you can build your confidence in yourself, and show those smucks that a negative attitude can't bring you down. They will respect you for it over time.