Former Shortland Street star KJ Apa now acts on the US drama Riverdale and acted in controversial film A Dog's Purpose.

Riverdale's Kiwi boy, KJ Apa is facing some serious backlash after he liked a fat-shaming post.

According to a report on MTV.com, Apa's eagle-eyed followers noticed he liked a comment on Instagram that was derogatory to overweight people. The comment appeared to excuse the bullying of overweight people by saying they deserved it, a screenshot that has circulated online showed.

The comment suggested it was moral to make "fun of fat people" because they deserved it and it would help them lose weight faster.

Apa was yet to address the screenshot, but had posted to Instagram saying he was excited for the release of controversial film A Dog's Purpose, in which he acted.

READ MORE:

* KJ Apa got death threats over involvement in A Dog's Purpose

* Cole Sprouse and KJ Apa put their bromance to the test

* KJ Apa got hacked by Riverdale castmate Cole Sprouse

On social media many fans expressed their disappointment at Apa.

me watching kj apa on #Riverdale tonight after his whole fat-shaming stunt: pic.twitter.com/5Zl1U8roF6 — Blanca x (@EleanorBased) April 28, 2017

can u believe kj apa liked a fat shaming comment on instagram pic.twitter.com/dZusuJ5YF5 — georgia 💗💜💙 (@ubercvrrntz) April 27, 2017

kj apa was my man.. not anymore i guess — alli (@maiagibbins) April 27, 2017

I think what hurt most was knowing how much I rooted for @kj_apa . I'm sure he didn't mean any malice but the fat shaming wasn't cool — River Zain Ceballos (@RiverC_Official) April 30, 2017

Riverdale, the show which has made Apa famous in the US, broadcaster Netflix was approached for comment.

The screenshot was understood to have surfaced over the weekend.

A Dog's Purpose was due out on May 4, it was based on W. Bruce Cameron's 2010 novel about a dog who learns his purpose as he is reincarnated into several dogs over the course of several lifetimes.

Despite its animal friendly theme, animal rights activists PETA called for a boycott of the film when video emerged of a dog being forced into churning water on the film's set.