go on / take up / start a diet

0Question #1: Which of the following sentences would you use?02br
02br
00Question #2 (natives only): Which is the most frequently used in your country?02br
02br
00a) I've decided to go on a diet.02br
02br
00b) I've decided to take up a diet.02br
02br
00c) I've decided to start a diet.0-