On a recent BBC Horizon, two identical twins went for a month on two separate diets. One of the twins ate a high carb low fat diet, the other did the reverse.

By the end of the experiment the one with the worse metabolical and biological outcomes was the twin on the high fat low carb diet. In fact the doctors told him to stop as he was becoming pre-diabetic.

link to bbc programme: http://www.bbc.co.uk/programmes/b03t8r4h