The Grapefruit Diet
The Grapefruit Diet has been around in some form or another since the 1930s, with the claim that grapefruits contain an enzyme that burns fat. While this may or may not actually be true, the thing that makes the Grapefruit Diet so successful is that its recommendation of eating half a grapefruit before every meal is paired with an overall low-calorie diet. So, you know, maybe just eat better.