The term "fad" diet is somewhat subjective but it generally refers to diet plans that either severely limit the kinds of foods you can eat or promote the use of supplements to cause weight loss. Fad diets typically promise rapid weight loss with little effort, the American Dietetic Association, and may not be a good option if you want to achieve healthy and sustainable weight loss.
Mayo Clinic Diet
The Mayo Clinic Diet is poorly named because, according to Every Diet website, it has never been endorsed by the Mayo Clinic health center. This diet emphasizes the consumption of grapefruit juice or grapefruit at every meal. In addition to the grapefruit, breakfast consists of two eggs and two slices of bacon. Lunch consists of grapefruit, meat and a salad. For dinner, dieters can have grapefruit, meat and any sort of vegetable. This diet also involves avoiding all breads, white vegetables, sweet potatoes and desserts.
The Atkins diet or other similar diets which restrict carbohydrates are considered by some to be "fad" diets, though they can help you lose weight at first, Mayo Clinic.com reports. These diets typically focus on consumption of meat, eggs, fish, poultry and non-starchy vegetables and exclude a food group, in this case, carbs. Most low-carbohydrate diets start off with a more restrictive menu and allow you to gradually increase your carbohydrate intake over time. These diets may help you lose weight by causing you to eat less due to the high amount of protein and the number of foods that are restricted, but are often difficult to sustain because they are so limiting, Mayo Clinic.com warns.
Blood Type Diet
The concept behind the blood type diet is that your blood type -- be it A, AB, B or O -- affects the types of food you should eat. People with type A blood should follow a mostly vegetarian diet, The Diet Channel website reports. If you have type B blood, you should eat a mix of animal and plant proteins and you should consume mostly red meat, fruits and vegetables if you have type O blood. The science behind this diet is suspect as there is very little evidence that your blood type affects how you respond to certain foods.
Acai Berry Diet
The Acai Berry Diet essentially involves acai berry to lose weight, Every Diet website reports. The acai berry is rich in antioxidants -- molecules that help prevent cell damage -- and may be useful for preventing some forms of cancer. On the other hand, claims that acai berry can aid weight loss are unsubstantiated by scientific evidence, and there are concerns about the quality of the supplements sold by some sources. The emphasis on a single source to lose weight is typically featured in "fad" diets.