Back in 2010, I lived with my best friend in San Francisco. We were business partners, best friends, and roommates who shared a one bedroom apartment (she slept on an air mattress in the living room). Because of our close quarters and mutual obsession with spending every moment together we possibly could, we ate essentially the same meals for a year. I’m a terrible cook, so she’d prepare meals—like some offbeat married couple (except without the sex, of course).

Over the months, we ate the same things, drank the same amount of alcohol, and exercised the same amount. (We were grossly obsessed with each other, and yes, I realize how ridiculous this all sounds.) The thing that struck me was that I was conducting an experiment without realizing it, because by the end of that year, I had gained weight and she hadn’t. My body, which has betrayed my will to not expand since I was a child, synthesized food and alcohol much differently than hers. I realize this is about as silly an “aha” moment as finding out the world is round, but it struck me as profound.

I realized that different bodies really do digest food differently. Some bodies store food as fat. Some bodies do not. Some metabolisms run well, others do not. Some people truly abuse their body with food and gain weight, while others truly abuse their body with food and stay thin. It goes against every medical advice we’ve ever been told about calories in and calories out. But, can it really be as simple as that?

Most people who bully the overweight have never experienced what it’s like to have their body betray them, to find that the thing which gives them life and sustenance creates unwanted results inside their bodies. 

What I’ve found is that the people who tend to rail against anyone who is overweight—especially on the internet—tend to be people who likely have never experienced the strange phenomenon that is weight gain. There are many people in this world who can simply eat whatever they want, never exercise, and never gain a pound. Those people don’t like to announce this fact, but it’s a fact whether they cop to it or not. I have been friends with many thin people who eat more than me and stay within the same weight range. I look at them and think, “If I ate like that, I’d gain like ten pounds a week.”

Most people who bully the overweight have never experienced what it’s like to have their body betray them, to find that the thing which gives them life and sustenance creates unwanted results inside their body. I’m sure many who have thin privilege also work out and eat moderately well, but that’s simple to do when you are not resentful of how food can double-cross your form. There’s an emotional component to weight gain that many who have not experienced it seem adamant about denying. It’s calories in and calories out and eat a salad and go to the gym, but never about the anger. There's a special brand of anger that can only be born from feeling like your own body is unpredictable in how it will digest food, that a simple pleasure like eating a good meal can turn into a regret.

I’m not advocating denying responsibility for the way your own body looks, but I am saying that there is a sense of thin privilege that exists—and the fact that it is so vehemently denied as if thinness is not a genetic trait—is problematic when it comes to advocating for healthy bodies. I’m sure anyone who has been thin their whole life can never understand what it’s like to gain weight so visibly and that’s OK. They can’t understand it. But that is even more reason to stop the bullying, to stop projecting your own experience onto people whose habits you can never understand simply by looking at them.

I know many overweight people who eat incredibly healthy, who exercise daily, and who do not see their weight change. This is something that people who experience thin privilege refuse to acknowledge—that weight is a weighty issue, something much more complicated and emotionally-charged than they can understand. That’s OK, they don’t need to understand the habits and situations for every person who has extra weight on their frame. But, they do need to acknowledge their own bias, their own sense of privilege which does not give them any right to generalize or to assume that their body is the same as everyone else’s body. It’s shortsightedness, at best; dangerous projecting, at worst.

As always, we need more compassion for those who struggle and for those we don’t understand because their experience does not match ours. This is true beyond the state of our bodies. That to talk with authority on something we know nothing about doesn’t just prevent us from moving forward, but is a significant step backward as well.

If you think weight loss is a simple equation—calories in, calories out—and there is no emotional component, no shame attached to it, no resentment, and  no anger, then, I’m sorry but your thin privilege is showing. Anyone who has watched as their body betray them knows that being overweight is never simple, never an easy physical fix. What we need less of are people who think they understand simply because they have a body. Not all bodies are the same. Not all experiences are the same. It seems a simple thing to understand and internalize, and yet, here we are.

Jamie Varon is a writer and cultural commentator living in Los Angeles. You can follow her on Twitter or like her on Facebook.