Nina Agdal in Bathing Suit is "One Year Wiser"

Happy birthday to Nina Agdal! The Sports Illustrated model just turned 31, and celebrated by sharing a picture of herself looking stunning (of course) in a tiny black bathing suit. "One year wiser. One year stronger. Welcoming 31 with gratitude 🙏," she captioned the post. How does she stay so fit? Read on to see 5 ways Agdal stays in shape and the photos that prove they work—and to get beach-ready yourself, don't miss these essential 30 Best-Ever Celebrity Bathing Suit Photos!

Agdal keeps her fitness and wellness routine consistent year-round. "I am all-year-round at this point, but I do want to say I've had very different relationships over time with fitness, wellness, and nutrition," she says. "The whole thing of the 'hot girl summer,' or 'summer body,' or all of these terms, can be extremely triggering to a lot of us. They put pressure on us to get in shape for the season coming up, and that's extremely hard on our mental health and our self-esteem. I really believe in finding something that can be a lifestyle and a healthy habit that makes you happy."

Agdal enjoys Greek yogurt and honey for a healthy breakfast. "Greek yogurt is a good source of calcium, magnesium and phosphorus – minerals essential for bone health," says registered nutritionist Nicola Shubrook. Indeed, studies suggest that diets which include foods, like yogurt, may support bone mineral density. When combined with lifestyle factors, like a resistance exercise programme, yogurt may help support bone strength through reducing bone resorption."

Agdal makes a point of exercising while traveling, even if it's just a small workout. "When I'm traveling, if I just get that 15 or 20 minutes in, (on the mat or on a towel or going for a jog outside to see where I am) it's always extremely helpful for me mentally," she says. "The most important thing I always tell people is to create great playlists that make you want to move. I always tell people, 'Don't bother bringing [equipment] with you. You can always use water bottles, you can use towels, you can go outside and use a chair.' But just make sure you have your playlist ready."

Agdal enjoys smoothies for a healthy snack. "Smoothie with peanut butter, bananas, blueberries," she says. "You have to have 11 blueberries every day, it makes your brain sharper—or I'll have a green juice."

Agdal understands the importance of doing what makes you happy. "Wellness to me is when you're happy on the inside and on the outside," she says. "If you're treating your body right, you'll feel happier, healthier, and stronger, which will show on the outside, as well. The most important thing for me is to be happy. Working out, eating healthy, and doing things I love make me happy. If I work hard, I can combine that with being able to have cheat meals every now and then without feeling guilty because I know I deserve it. That's the ultimate goal."