Actress Kate Hudson — whose rock-hard abs are nearly as impressive as her film career — considers a high-alkaline diet the starting point to getting fit and firm. “Our bodies are one large chemistry experiment,” the star has said of the approach — which argues that changing the pH of your body improves health — adding that, by following it, “I can control my body to look the way I want it to look.”

The 39-year-old actress isn’t the only celebrity who swears by this particular approach to healthy eatingJennifer Aniston, Jared Leto, Kirsten Dunst and Victoria Beckham are all fans. So how exactly does it work? The diet is based on the theory that different types of food leave behind different types of waste — by-products that can be acidic, alkaline or neutral.

Acidic foods are thought to weaken the immune system and contribute to bone and muscle damage; conversely, alkaline foods are believed to improve health as well as physical integrity. By bringing your body to an optimal pH level, proponents of the diet argue, you can not only reduce disease and lose weight, but also enhance your energy levels, strengthen your immune system and improve digestion and sleep. “That’s my go-to,” Kate has said. “It’s no dairy, wheat, meat, or sugar, and it’s gluten-free. And no wine and no beer — only vodka and tequila, straight up.”

When she sticks to the plan, she gets 60 to 80 percent of her caloric intake from foods like tofu, nuts and most fruits and vegetables. She does make an exception for lean meats, “but only occasionally — animal protein has a highly acidic effect on the body and causes inflammation.”

While medical studies have yet to confirm the theory behind this diet, there’s certainly no harm in fostering healthy eating habits. And for Kate, there’s plenty of room for trial — and even more for error. “If I want to go out and eat at a restaurant with amazing food, I’ll do that,” she said — but she’ll try and “keep it light” beforehand. Kate’s normal day-to-day meals include lentil tacos, gluten-free pasta with veggies, steamed fish “in greaseproof paper,” almond milk-based butternut squash soup, and vegetable stir-fry over brown rice.

But to maintain her incredible figure, Kate does more than just eat right. “If I’m not doing something active, I don’t feel good,” said the Almost Famous star, who’s been practicing Pilates for 15-plus years. Apart from the core-focused routines, she does everything from SoulCycle to Bella Core (a ballet barre class) to Tracy Anderson to the Brazil Butt Lift DVD series. At home, she has no qualms about locking herself in a room and dancing her feet off. “I’ll turn music on as loud as possible and just get weird. “It just makes me feel so much better.”

Kate, who’s mom to two boys and a girl — Ryder, 14, Bingham, 7, and Rani, 3 months — got a particularly healthy start in life. Her own mother, the still-stunning Goldie Hawn, taught her the value of both smart eating and regular exercise. But that’s not all that matters, she knows. In fact, the secret to a happy life, Goldie’s said, may have less to do with diet and more to do with quiet. Revealed the 72-year-old “glamma” — who’s meditated every day for the past 50 years — “Everyone in Hollywood seemed all screwed up and I didn’t want to be like that… I wanted life to be fuller.”

In 2016, Kate released her self-help book, Pretty Happy: Healthy Ways to Love Your Body, the culmination of years of dedicated journaling that helped reveal personal patterns. “I’m finally at a place in my life where if someone wants to know what I do to stay healthy, why not tell them?” she explained. She’s also the cofounder of the trendy women’s athleisure line Fabletics, which began as an e-commerce site but now plans to open more than 100 retail locations over the next few years. “I wanted to create something that was more about a lifestyle than an actual fitness brand,” Kate said, adding proudly, “It seemed to really resonate.”