[saef]

This thread is making me think of the soprano Deborah Voigt. Look her up on Wikipedia & in particular read about "The Little Black Dress" incident. Voigt is a talented & famous opera singer who lost a high-profile singing job in 2004 because she could no longer fit in the dress that the director wanted her to wear in the production. There was a lot of discussion of this in the press at the time. (I was a Metropolitan Opera subscriber at the time & may have followed it more closely than your average non-opera-fan, so I remember it well.) She underwent gastric bypass surgery & lost a great deal of weight. Her career was helped by her weight loss. I do not believe that her voice changed. It would be a great question to ask her, or to compare recordings made by her before & after.

[arumaru]

I highly doubt that, unless your obesity was caused by hormonal or thyroid problems. Aging does change people's voices though. A 45 year old woman doesn't usually sound the same as an 18 year old woman.