Demi Lovato thinks "complimenting someone on their weight loss" can be dangerous.

Demi Lovato

Demi Lovato

The chart-topping pop star has warned that weight-loss compliments can having a damaging impact on a person's mental health.

Demi, 28, wrote on Instagram Story: "Idk who needs to hear this but complimenting someone on their weight loss can be as harmful as complimenting someone on their weight gain in regards to talking to someone in recovery from an eating disorder.

"If you don't know someone's history with food, please don't comment on their body. Because even if your intention is pure, it might leave that person awake at 2 am overthinking that statement… (sic)"

Demi - who has struggled with addiction and an eating disorder - warned fans of the potentially destructive impact of weight-loss comments.

The post continued: "Does it feel great? Yeah, sometimes. But only to the loud a** eating disorder voice inside my head that says 'See, people like a thinner you' or 'if you eat less you'll lose even more weight.'

"But it can also sometimes suck because then I start thinking 'Well, damn. What'd they think of my body before?' Moral of the story: I am more than the shell for my soul that is my body and everyday I fight to remind myself of that, so I'm asking you to please not remind me that that is all people see of me sometimes. [heart and prayer emojis] (sic)"

Meanwhile, Demi recently came out as non-binary.

The 'Cool for the Summer' hitmaker announced the news via a series of Twitter posts, confirming plans to change their pronouns from she/her to they/them.

In a video posted on Twitter, Demi explained: "I want to take this moment to share something very personal with you. Over the past year-and-a-half I've been doing some healing and self-reflective work, and through this work I've had the revelation that I identify as non-binary.

"With that said, I'll be officially changing my pronouns to they/them. I feel that this best represents the fluidity I feel in my gender expression and allows me to feel most authentic and true to the person I both know I am and still am discovering."