Here's a good rule: Don't post a photo of a stranger on social media only to mock their appearance, and definitely don't do this to someone at the gym.

Unfortunately, bodybuilder Diana Andrews was apparently unaware of this taboo.

Andrews is embroiled in a body-shaming scandal after posting a photo of another person working out and making fun of their “love handles.” Another one of her posts speculated the person might be ordering hamburgers for delivery.

She has since apologized, but the reactions to her original posts were swift and appropriately outraged.

Followers of Andrews quickly jumped in to highlight the problem.

The episode serves as an example of why people have anxieties about going to the gym and demonstrates the toxic body-policing culture that manifests itself, for example, in 94 percent of teenage girls being shamed for how they look. Social media body shaming can also lead to eating disorders.

This isn’t the first time this has happened, either.

What makes this matter worse is that a very similar problem occurred last July.

Playboy model Dani Mathers was at the center of a social media body-shaming controversy after posting a nude image of a stranger on her Snapchat, commenting: “if I can’t unsee this then you can’t either.”

Don’t be mean on social media — and don’t body shame anyone.

Andrews has since apologized (twice, actually) and has made her Instagram account private.

"I'm always encouraging ppl do do their best and push them selfs," Andrews wrote in a Facebook post. "I'm here to motivate especially women...I deeply regret that I took that video."

Situations like this are a very big reminder that what we post on social media doesn’t happen in a vacuum. In fact, there is ample psychological research associating social media culture with concerns with body image.