The 26-year-old actress has seen her weight fluctuate in the past but she has now found her perfect size - a UK size 10 - and has told friends it`s a relief not to be on a constant diet.
A source told heat magazine: "Mischa`s grown tired of doing extreme fasts and cleanses to try and drop weight quickly and then putting it all back on. She`s healthier than ever, following a vegan eating plan - but she`s not calorie counting.
"Mischa`s been through the wringer with her body. Her weight has massively fluctuated over the years, after falling off and on the diet wagon, but now she`s giving herself a break."
Last year, Mischa has said she was pleased with how she looks, saying: "I`m proud of my body. I eat healthily and sometimes I pig out. But I exercise regularly.
"Everybody has things that they are conscious of. I talk about this with my girlfriends all the time. We work out and we eat healthy and we do what we do. I feel very comfortable. You are what you are as a woman."