The America's Next Top Model presenter, who was once so famous for her shapely curves, is looking very slender after changing her diet.
'Tyra started feeling sluggish in the spring, so since then she's cut out all sugar, white flour and processed foods,' says our insider.
'She's also been reading a lot about veganism.'
It's a far cry from the Tyra of 2006, who famously said she 'still feels hot' at her heaviest and revealed that she maintained her fuller figure with ice cream and calorie-laden salads piled high 'with ranch dressing, croutons and bacon bits'.
She also came out all guns blazing later that year when she was branded 'America's Next Top Waddle', saying: 'To all of you who have something nasty to say to me or to women built like me: kiss my fat ass!'
However, it seems the 36-year-old has drastically changed her body outlook and those around her fear she could take her weight loss too far.
Our insider says: 'When Tyra was heavier, she wanted everyone to think she loved her curves, but it'd be more accurate to say she was accepting of her curves.
'At the end of the day, she's made her name as a fashion model and she'd love to be pin-thin for the rest of her life.'
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