Kim Kardashian gets serious about weight loss in bid to shed the 20lbs she's gained since dating Kanye West

She says that she is serious about slimming down since gaining a reported 15-20 pounds during her relationship with Kanye West.

And in a concerted effort to shift the weight, Kim Kardashian slipped on a pair of geeky black-rimmed reading glasses to work-out on the beach on Wednesday.

However, her more conservative and smarter style failed to distract from her sexy curves as she did some strenuous lunges on the sand.

  The 31-year-old displayed plenty of cleavage in a black sheer tank top, which she paired with tight leggings, that in turn highlighted her famous derriere.

Kim has admitted that she has put on weight, and tells Life & Stye she's determined to get back into shape after letting herself go since dating beau West.

'I’m hoping to slim down a little bit, and I’m not afraid to say it,' she tells the magazine in their latest issue.

'I’ve started [diet supplement] QuickTrim again,' she says. 'When I start that, it’s full focus.'

On Wednesday during her work-out, the reality star was also joined by her sister Kourtney and their Real Housewives Of Miami pal, Larsa Pippen.

The trio were seen going for a jog - the exercise session recorded by a film crew for the sister's new reality show.

 Tying her hair back in a ponytail and toning down her usual full-force of make-up, Kim slipped her  spectacles on and off during the workout.