Jack Osbourne has scathing message to critics claiming he's 'grossly underweight' as he reveals truth about weight loss

Jack Osbourne, son of rock legend Ozzie, has undergone some huge changes since he made his debut on our television screens back in 2002's The Osbournes.

You could argue he's in the best shape of his life, something he puts down to huge lifestyle changes, which include a long stint of Muay Thai martial arts training at a camp in Thailand.

He said prior to this, his weight shot up to 220 pounds, which caused him to take a long hard look at himself.

However he has recently found himself on the receiving end of some abuse online, and he furiously took to TikTok to defend his new-found svelte figure.

Osbourne, who has recently become a dad again, expressed complete disbelief that he "had to make this f***king video."

He said: “If I see one more article written about me saying how ‘I’m sick, I’m grossly underweight.’

“What’s going on? It’s f***ing insane.”

The Osbourne's back in 2002 (Kevin Winter/Getty Images)

The reality TV star said that he had lost no weight since he left the jungle where he was going I'm A Celebrity, six months ago.

He continued: “I’ve been the same f***ing weight. The only difference is I shaved my beard and opted for a creepy moustache.

“That’s the only f***ing difference."

Jack Osbourne is looking healthy and happy these days (Tommaso Boddi/WireImage)

Osbourne went on to detail the battle he has had with his weight over the years, but that he was proud of how far he had come.

He decided to ditch booze and drugs in his 20s, in a huge turnaround from his rebellious early years.

How much weight has Jack Osbourne lost?

He said: "Now if we want to back up and we want to get real f***ing personal, I’ve been consistently but slowly losing weight for the last three and a half years.

"I shot up to about 220 pounds three and a half years ago and decided that I wanted to make some changes.

“So I did. What’s the big fucking deal?"

He added that he was five foot eight and weighed 155 pounds, which he suggested was "perfectly healthy".

There have been plenty of comments made online about Jack, Kelly and Sharon Osbourne's weight (Amy Sussman/Getty Images)

His transformation formed part of a reality TV show, Jack Osbourne, Adrenaline Junkie, where he shed a massive 70-pounds.

In March, Jack, who is married to Aree Gearhart, announced his wife had welcomed a new baby girl. The pair have two kids together: Maple Artemis Osbourne and Ozzy Matilda Osbourne. He has a further three kids with his ex-wife, Lisa Stelly.

In an Instagram snap posted at the time, the tot was pictured lying peacefully next to what appeared to be a bat plushie and a badge that said ‘Hello World’.