Stiles grew up outside Morris, Illinois. Her mother designed, without any professional experience, their passive solar home and built it together with her father, now retired from a career in nuclear power. She has one sibling, an elder brother, Chad, who is an electrician.

Stiles studied dance from a young age. A local photographer brought her to Marie Anderson Boyd, founder of Aria Models in Chicago, later acquired by Ford Models, who signed her on the spot. Boyd booked Stiles' first casting, an ad campaign for Coca-Cola, and Tara moved to New York City soon after.

Stiles has been featured in pictorials for W, Shape Magazine, Self, Marie Claire, Fitness, and appeared on the covers of City, Time Out, and Fit Yoga. Stiles appeared in ads for Nike, Adidas, Reebok, Target Corporation, Gap, and American Apparel, as well as numerous TV commercials for the Chrysler PT Cruiser and Avon. Stiles' health and yoga related work has been featured in such magazines as Esquire, Men's Health, and Yoga Journal.

Stiles founded the New York City yoga studio Strala.

Stiles collaborated with Watch It Now Entertainment to create her Yoga Anywhere DVD series, whom she also worked with on Elle magazine's Make Better Yoga Workout with Brooklyn Decker.

Stiles has been the Face of Women's Health, a Rodale, Inc. publication, since April 2009. Stiles is also a spokesperson for Nissan Motors, along with Ryan Hall, and Lance Armstrong.

Stiles was a contestant and winner of MTV's Fear episode 9, "Fort Gains". She has also appeared in Matthew Barney's The Cremaster Cycle: Cremester 3. She co-hosted three segments on LX-TV on fitness and fashion with Pedro Andrade, Siafa Lewis, and Margherita Missoni.

Stiles is a blogger and on-camera correspondent for the Huffington Post. Stiles' work covers health, yoga, social, and political issues, and pop culture. She wrote the most viewed post in the website's history, "Help! I'm Addicted to Facebook." She interviewed Donna Karan about Karan's work with Urban Zen. Stiles pens a Q&A column in Women's Health magazine.

Stiles' debut book, Slim Calm Sexy, published by Rodale, rose to the #1 spot on Amazon and best selling status its first week released, August 31, 2010.

Stiles met technology entrepreneur and CEO of Odyl, Michael Taylor, in 2007 at a yoga and meditation retreat at Ananda Ashram led by Yoga's Rock Star Krishna Das, and Dharma Mittra. The couple got engaged during Thanksgiving weekend the same year in Zermatt, and were married in a private ceremony in Jamaica on August 22, 2008.