Reality Star Ruby -- Hiking Her Ass Off

6/22/2010 4:27 AM PDT
Style Network's weight loss superstar Ruby Gettinger just conquered one of the most punishing mountains in L.A. ... on a scorching hot day ... not bad for someone who could barely walk for 5 mins in 2008. 

Yesterday, a slimmer, trimmer Ruby -- who once weighed in at 750 pounds -- impressively hiked her way up to the top of Runyon Canyon ... where the reality star dished up some awesome advice on keeping the weight off.