After Biggest Loser alum Bob Harper called out Jillian Michaels for not checking in on him following his 2017 heart attack, Jillian reacted to his comments.

For years, Bob Harper and Jillian Michaels appeared to have great chemistry onscreen while filming "The Biggest Loser" together. But a new docuseries about the NBC weight-loss competition has fans wondering if the dynamic duo actually got along in real life.