'Biggest Loser' David Fioravanti Says Jillian Michaels Never Gave Him Caffeine Pills

Jillian Michaels didn't get along with every contestant on "The Biggest Loser" ... but, that doesn't mean she was handing out caffeine pills like a new documentary suggests -- so says one of the OG Losers.

We spoke with David Fioravanti -- a contestant from the first season of the show -- and, he details his contentious relationship with the fitness trainer and former coach on the show.

Fioravanti says he came into the show with a basic level of fitness knowledge ... so, he didn't follow everything Michaels said without question.

The way David puts it ... if Jillian told contestants to eat sand to lose weight -- which to be clear, she never did -- they would. However, he pushed back when he disagreed, setting up some explosive moments.

Fioravanti tells us he thinks Jillian tried to influence who stayed on the show and who got kicked off ... especially in his case -- but, he never saw her give anyone in his season caffeine pills or anything else to lose weight.

There was one trick Fioravanti says Michaels taught them ... which involved contestants smearing Preparation H on their skin to take out water weight the night before a weigh-in.

This resulted in a lower posted weight -- but, Fioravanti makes it clear that he doesn't think this was dangerous in any way, shape, or form. As far as we know, Preparation H was allowed on the show.

As you know ... Michaels is considering suing the creators of a new Netflix documentary about "The Biggest Loser" which includes testimony from Dr. Robert Huizenga claiming he never worked with her on safety measures for contestants.

The documentary also claims she gave contestants caffeine pills -- a banned substance.

Jillian called us directly this morning and talked about the documentary in a bombshell convo ... check it all out to hear what she's got to say.