Billie Eilish in Bathing Suit Shares Rare 4th of July Selfie

Billie Eilish just shared a swimsuit selfie, a few days after headline Glastonbury, making for a very happy 4th of July. (She rarely poses in swimwear.) The megastar is seen in a mirror, as two friends are behind her, one holding a dog. It's been a banner year for the talent, winning an Oscar and headlining concerts. How does she stay so fit? Read on to see 5 ways Billie Eilish 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!

She enjoys doing yoga when she's not taking a dance class. Yoga makes her more flexible and helps her reach her fitness and strength goals. It's the perfect low impact workout to practice that will prepare her for her performances. "A number of studies have shown that yoga may help reduce stress and anxiety. Yoga can enhance your mood and overall sense of well-being. Yoga might also help you manage your symptoms of depression and anxiety that are due to difficult situations," says the Mayo Clinic. "Practicing yoga may lead to improved balance, flexibility, range of motion and strength."

Although there's not much out there about her specific workout routine, Billie loves to perform and dance. If you've seen her perform live or on TV she can often be seen running around on stage which can keep her healthy and fit. "When you start out on your run, your body goes through a transition: Your breathing may become heavy, and you might notice your pulse quicken as the heart pumps harder to move oxygenated blood to your muscles and brain," says Hopkins Medicine.

In addition to bopping around on stage while performing and staying active, she actually likes to dance in a competitive form. Billie takes professional dance classes 3 to 4 times a week that are usually around 90 minutes or longer. "Dancing is a popular form of physical exercise and studies have show that dancing can decrease anxiety, increase self-esteem, and improve psychological wellbeing," says one study.

Billie Eilish hasn't been one to shy away from talking about body image and hiding that from internet trolls ready to judge her. She has shared her struggle with fans about her mental health journey and pressure to be thin. Wearing her signature loose fitting clothes (although, she strays from the look on occasions with gowns) took some of that pressure off her shoulders.

Like others in the field like Ellen DeGeneres and Miley Cyrus, Billie Eilish is vegan. Although veganism has been proven to have a lot of health benefits, Billie did it because she loves animals. She hasn't been shy when it comes to expressing her feelings about cruelty towards them. "The key to a healthy vegetarian diet, as with all diets, is to include a variety of foods. No single food can provide all the nutrients your body needs. It's especially important for older adults to be aware of their nutritional needs, since aging can increase the risk of nutritional deficiencies. Talk with your doctor or a registered dietitian about developing a healthy vegetarian eating plan that meets your needs," says the Mayo Clinic.