After Cassie shared her engagement, a message from a personal trainer landed in her inbox.

Earlier this month, on the eve of their 10 year anniversary, Cassie Young’s boyfriend proposed.

A radio host in the US, Cassie was quickly flooded with messages of congratulations from her friends, family and colleagues.

But there was one message Cassie couldn’t ignore, from a personal trainer who had offered up his services to help her “get in shape” for big day.

While the bride-to-be had no problem with his original offer, things quickly went downhill when she declined his help.

“I know you want to look the best on your wedding day,” the trainer – who hasn’t been named – responded.

“If you don’t hire me hire someone. Those pictures last for centuries. Your children’s children’s children will still have those pictures.”

Cassie replied that she would look her best “because I’ll be so happy I get to marry the man I love” before telling the trainer it has taken her a long time to love and accept her body.

"I'm constantly shamed or reminded that I'm heavy and I should be embarrassed," she wrote.

"I've battled past all that and like myself and how I look.

"The idea of me being embarrassed by my wedding pictures because I might be "fat" in them and people centuries from now will be ridiculing me? That's the insinuation and I say f*** that noise!"

But the trainer wasn't interested in hearing Cassie's body-positive message, telling her she was "lying to herself".

"You can accept how you look but you can't be happy with the way you look," he wrote.

"I just wish the whole big body acceptance people would accept the fact that they are not happy with their bodies."

He added that people only feel "fat shamed" because they have "something to be ashamed of".

Cassie responded that she was "sad" that the trainer's self-worth was "wrapped up" in his looks, and shared screen-shots of the entire conversation on Facebook.

"I want every woman and man to know that it does not MATTER what you look like," she wrote.

"You are worthy. Love is out there for you. Life is waiting with open arms. It doesn't matter if you’re skinny or fat or between the two or willowy or broad shouldered or peer shaped or like a board or anything in between.

"You get good stuff in life by being YOU. That's what matters."

LISTEN: Mamamia Out Loud's Jessie Stephens shares how she felt body-shamed by her own gym.

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