Tyra Banks looked about thirty pounds lighter at the BET Awards show a few weeks ago, and now FOX411 knows why.

Banks is on a serious diet - so serious she's banning people around her from eating, too!

"She has become so strict with her diet that she can't even stand for junk food or fattening food to be around her," a source close to the talk show host tells FOX411. "So she's basically telling anyone she eats with what they can and can't order."

So how are her hangers-on handling the involuntary diet restrictions?

"Most people think she's joking at first, but then they realize she actually expects them to follow her eating rules too."

It doesn't sound like she's being too vague.

"She tells them: 'If I'm not eating it, you're not eating it!'" says the source.

So what do her pals gets to eat? The insider says Banks has been following a healthy diet of natural foods, lean meats and proteins, plenty of fruits and vegetables, and lots of glasses of water.

Doesn't sounds so bad.