The Hills star had her chest enhanced to a G-cup earlier this year but has now reportedly decided that she wants to return to her "normal" size.
"I'm desperate to go back to normal. I'm downgrading and going a little smaller, to a D or a double D," she explained to Life & Style.
"I'm obsessed with fitness but it's impossible to work out with these boobs. It's heartbreaking. I can't live an everyday life."
The 23-year-old also reportedly confessed to feeling "trapped" in her body and worried that she might never regain her former figure following the death of her plastic surgeon Dr Frank Ryan last week.
"I feel trapped in my own body... There's just no fixing it. Dr Ryan knows the work he did, he knows everything."
Montag had her chest enlarged in November on the same day that she underwent a further nine cosmetic surgery procedures.
