Kimberly Stewart says hiking stops her from going mad.The model, the daughter of rocker Rod Stewart, admits she is a fitness fanatic and loves to hike but insists she is not doing it to stay slim - but to maintain her spiritual balance.She said: "I do a lot of exercise. I do yoga and work out about four times a week. I also hike. But a lot of what I do is for spiritual reasons - it keeps me balanced and sane!"Meanwhile, Kimberly has revealed she wants a Londoner to sweep her off her feet.The 26-year-old blonde says she is desperate to date a man from the UK capital because they make her laugh.She said: "I prefer London guys because I love the British sense of humour. It's probably because my dad has that sense of humour."