Shay Mitchell's critics called her before and after photo harmful. Experts agree.

Editor's note: This story has been updated.

When Shay Mitchell shared a "before and after" photo to Instagram recently, the 33-year-old was flooded with supportive affirmations from her celebrity friends. In the post, which was paid for by the fitness brand Open Fit, Mitchell wrote that "in just 4 weeks I have felt more fit than I have in a long time, and already have the results to show." But she was also met with critics calling her out for perpetuating fatphobia and diet culture. And according to experts, they wouldn't be wrong.

According to Dr. Anisha Patel-Dunn, Psychiatrist & Chief Medical Officer at LifeStance Health, before and after photos, regardless of the motivation behind them, can be detrimental. “Whenever you see someone who has lost weight on social media, there is such an emphasis on how much better they look in the after.”

When anyone sees a comparison picture, it has the potential to exude a false illusion of reality. “In that moment, there is a visual implantation in your brain of what you want to look like, or used to look like, that almost always ends up being disconnected from reality,” Patel-Dunn explains. This happens most frequently with younger people who are more impressionable.

This is also a problem because of the emphasis on size and shape, and not necessarily on health, Frank J. Sileo, a licensed psychologist in Ridgewood N.J. and award-winning author, says, adding that “before and after photos place too much emphasis on the outer appearance when the reality is that being healthy involves other factors such as having a healthy mind, good internal systems (i.e., circulatory, digestive, etc.).”

Another reason why before and afters are so damaging is that people tend to forget that these photos are usually the direct result of a product or experience, like a new diet or fitness trend. In other words, the person posting the comparison is trying to get you to buy something, usually without regulations. While many adults can decipher between these marketing tactics, for children, it's hard to do and can lead to dietary disorders, self-esteem issues, anxiety and depression among other damaging consequences.

Patel-Dunn goes so far as to call diet industry advertising tactics "almost as egregious" as those employed by the tobacco industry. “It is the same smart marketing people just trying to sell you a product to make money. It is taking advantage of the vulnerability of the socioeconomically poor and of children.”

Ultimately, experts agree that diet culture is dangerous and before and after images play into that. And when someone experiencing body image concerns comes face to face with these before and after comparisons, it creates the idea that they themselves are not good enough as they are.

Of course, not all before and after photos are bad — some do see the value in utilizing them for inspiration and motivation. And Mitchell's has great parts too. As the Pretty Little Liars star wrote, she "learned about physical and mental self-care, and made a pact with myself that 2021 would be different. I wanted to focus on myself again, because I’m the best version of myself for Atlas — and everyone else — when I take care of myself first." Prioritizing one's mental and physical wellness? Now that's a message everyone can get behind.

Read more from Yahoo Life:

• Model Hunter McGrady says ‘being larger than your partner is OK. I certainly am!’

• Amy Schumer tells Hunter McGrady that she 'rejects' media's emphasis on weight: 'It's so negative'

• Victoria's Secret fans are praising its body-inclusive swimsuit campaign: 'Yeees curvy queen!'

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