Grapefruit contains enzymes that make our body burn fat for energy, resulting in quick and easy weight loss.

Although there are quite a few different versions of this plan, all require that you eat half a grapefruit before every meal to reap the benefits of the fat-burning enzymes. Calories typically are limited to less than 800 per day, although some versions require that you "eat until you are stuffed."

The grapefruit diet has been around in some form for decades. In general, weight loss comes from the extremely low calorie intake.

• Great if you love grapefruit.
  
  
• Grapefruit has no fat, is low in calories and sodium, and is packed with vitamin C; the pink variety contributes beta-carotene.
  
  
• Also good for coffee drinkers, as coffee is strongly encouraged.
  
  
• No calorie counting.
  
  
• Quick weight loss.

• Not so great if you don't love grapefruit.
  
  
• The very low-calorie diet and encouragement to drink copious amounts of beverages containing caffeine make this diet dangerous.
  
  
• Can be even more dangerous for people taking prescription medications. Many prescription drugs have adverse interactions with grapefruit juice.
  
  
• Low in protein, fiber and several important vitamins and minerals.
  
  
• Any diet that relies so much on a single food is too restrictive.