We're with Pilates trainer Hollie Grant who advises: 'Don't run. I used to run marathons, but while running may cause weight loss in some people, it can also cause a flattening of your bottom,, and for many it just doesn't trigger fat loss at all. Do it for sanity or enjoyment but don't expect it to change your body shape. For that you need to add some kind of weights element - be it strength training, body-weight training or Pilates.'