"Our bodies are one large chemistry experiment," says the actress in this week's issue of PEOPLE.
In her new lifestyle book, Pretty Happy: Healthy Ways to Love Your Body, Hudson, 36, shares that she now follows a high-alkaline diet, which means she tries to get 60 to 80 percent of her caloric intake from foods like tofu, nuts and most fruits and vegetables.
Never one to step on the scale ("I don't need to unless I start to see myself getting off track"), the actress tries to limit her meat consumption.
Lean meat is fine, she says, "but only occasionally – animal protein has a highly acidic effect on the body and causes inflammation."
For more of Hudson's interview, including an exclusive excerpt from her new book, pick up this week's issue of PEOPLE on newsstands Friday.
The Kung Fu Panda 3 star also relies on food delivery services, like Sakara, to help keep herself on track.
"I use them a lot. They're excellent," she says. "It's hard because diet delivery serves are expensive. But it's nice to do a clean out for a week and be super healthy."
Hudson says that although she was never an "emotional eater," she has made bad choices about food sometimes.
"Now, after a lot of trial and error, I've figured out how not to overthink what I eat," she writes. "I don't restrict myself … I've learned to enjoy new foods and new ways to be inside my body – and there are always new options to discover."