D.I.E.T. (Did I Eat That?) by Sarah Zolton Arthur

In the fight between food bites and love bites, love bites rule…

When the funny, friendly, most-might-say pretty, but-all-would-say chubby Brigeeta—or Geet—as her best friends call her, gets an invitation to her besties’ wedding, she couldn’t be happier… until she finds out is the location.
A destination wedding? Seems appropriate for Kami and Len, but they’re giving their vows on an island close to Antarctica. There’s hiking involved… and like seventy-bajillion steps to climb. How in the world is she expected to make it all the way up there?
But wait—it gets worse. The invitation says Brigeeta + 1. A plus one? Kami has to know there hasn’t been a plus one in like, forever… or at least for the last couple of years.
Her new personal trainer is pretty hot and might make a good candidate for a plus one if not for Sinjin, the goofy, highly annoying, unbearably attractive workaholic the trainer paired her to partner with to keep them motivated, who also makes her reevaluate her ideas about love.
Brigeeta has six weeks to get in shape enough to make the trek to her best friend’s wedding, and six weeks to convince the guy she wants to go along with her that picking her over work might just lead to the greatest adventure of his life.