The 35-year-old actress - who allegedly had breast implants and a nose job in 2010 - thinks people should focus on how she treats people instead of how she looks.
The 'Almost Famous' star said: "That's like asking someone if they see a therapist--and why? If someone wants to go get butt implants, then sure, go get butt implants. The real question is, How do they treat the person next to them? Are they a**holes or are they awesome?"
The blonde beauty isn't a fan of the paparazzi or bloggers.
She told the July issue of InStyle magazine: "I just look at the paparazzi and mentally cut their heads off.
"The negativity is just so vast. Will everybody stop being so damned judgmental?"
But Kate - who is engaged to Muse frontman Matthew Bellamy - insists she has no regrets about following in her mother Goldie Hawn and stepfather Kurt Russell's footsteps in Hollywood, and claims she doesn't strive for "perfection" in her life.
The 'Wish I Was Here' actress, who has 10-year-old son Ryder from her marriage to Chris Robinson and two-year-old son Bingham with Matt, said: "I joined the circus because I wanted to be part of the circus. I have a rebelliousness in me. I'm not interested in perfection--that's the whole point!"