Why Don't Fad Diets Work?

Brown fat first began mystifying scientists three decades ago, when it was determined to act as a calorie-burning heat source. (Image credit: Nruboc | Dreamstime)

The bevy of diets available to consumers is overwhelming from Slim-Fast to the acai berry diet, there always seems to be a new diet hitting the market. But, as many people struggling to lose weight already know, dieters that follow fad diets are rarely successful.

Even when a diet leads to weight loss, the lost pounds are often gained back within a few years, months or even weeks. In 2007, researchers at the University of California, Los Angeles (UCLA), reviewed 31 long-term studies lasting between 2 to 5 years and concluded that a very at least one-third to two-thirds of people on diets regain more weight than they lost within four or five years, and the true number may well be significantly higher.

With this astronomical failure rate, why are fad diets still popular? Below are three types of fad diets, and why each one is destined to fail.

Food combination diets (Example: Suzanne Somers' Somersizing Diet Plan)

In these diets, food is eaten in a particular order. For example, a diet's many rules and regulations may prohibit eating proteins and carbohydrates together, requiring a person on this diet to wait at least four hours between meals so as to not mix them. Other restrictions could include eating only one kind of protein at a meal, eating protein and acidic foods (such as orange juice) at separate meals, eating proteins and fats at separate meals and not eating proteins and sugars (including fruit) together.

"Diets with that many rules and regulations are very hard to follow for an extended period of time," said Nancy Clark, a registered dietician and sports nutritionist in Boston and author of "Nancy Clark's Sports Nutrition Guidebook" (Human Kinetics Publishers, 2008). "A person should never start an eating program that they can't maintain for the rest of their life."

Diets that illogically overemphasize a single food (Example: the grapefruit diet)

Diets that revolve around eating one food , be it cabbage soup or bananas, are unhealthy because they severely restrict most other foods which is a recipe for a nutritional deficiency. Most dieters soon find that following a strict routine of mainly eating one food day in and day out quickly leads to diet fatigue, which is why these types of diets are typically designed to only last several weeks.

"We concluded most of them would have been better off not going on the diet at all," said Traci Mann, associate professor of psychology and lead author of the UCLA study. "Their weight would be pretty much the same, and their bodies would not suffer the wear and tear from losing weight and gaining it all back."

Eating mostly one food group (Example: the Atkins diet)

Irrational food instructions, including food restrictions such as not eating any carbohydrates, fruit or fatsare not only extremely hard to follow and stick to, but also make people avoid food that their bodies need. For example, diets that aim to completely cut out fat are based on a dangerous oversimplification that overlooks the fact that the brain and nervous system require certain levels of fat in order to function properly.

"The current trend seems to be to market a diet as a lifestyle change," said Jenni Schaefer, author of Goodbye Ed, Hello Me: Recover From Your Eating Disorder and Fall in Love with Life (McGraw-Hill, 2009). "People must be wary of so-called 'lifestyle changes' that are actually diets. A true lifestyle change will not require rigid rules and drastic measures."

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Remy Melina was a staff writer for Live Science from 2010 to 2012. She holds a bachelor’s degree in Communication from Hofstra University where she graduated with honors.