Here's an idea:  the Eat-All-You-Want diet. Plant a garden a mile from your house.  Walk to the garden.  Gather as much food as you want, of any kind.  Eat as much as you can.  Walk home.  Do this all day, every day. You must walk to the garden, you can't use any other mode of transportation.  You must do all the planting, tilling, harvesting, etc. How many do you think would sign up for that diet?