Jillian Michaels has rubbished allegations made against her on Fit for TV: The Reality of the Biggest Loser

Alongside an old email chain from her time on the show, Jillian wrote on Instagram: "Here is an email chain with @bobharper - the Biggest Loser's producers - @drhuizenga's guy, Sandy Krum, who stayed on set with us and distributed the fat burners about which "fat burners" / caffeine pills to purchase the contestants. This is one email of many that shows:

"- Dr. Huizenga did approve caffeine pills on many seasons of Biggest Loser.

"- Bob Harper not only knew about the caffeine pills the "stackers fat burner" were actually his suggestion. I wanted to use my brand instead because they were cleaner and had no more than 200mg of caffeine (equivalent to a strong cup of coffee).

"- Caffeine was NEVER banned on The Biggest Loser.

"Wild how some folks still lie like it's 1985 before texts and email were a thing. (sic)"

By contrast, Dr. Robert Huizenga - the celebrity doctor who starred on The Biggest Loser - previously revealed that he clashed with Jillian and Bob about their approach to the show and the contestants.

He said on the docu-series: "It was scary because from season 1, you have women - 200 lbs., men - 300, and it just went up, straight line up. And with that, the ability to exercise, a straight line down. So when they do a physical challenge that puts people in harm's way, that's where I have to step in."

Dr. Huizenga admitted to feeling uncomfortable with some of the things he witnessed.

He said: "There were times, unfortunately though, that challenges were done that I didn't see or hear about, which was the main hang-up to making it a much safer environment."