Truth Squad: Feast-and-Famine Diet and Other Diet Trends takes a look at the best and the worst fad diets.

ByABC News
November 25, 2009, 5:47 AM

Nov. 30, 2009— -- With Thanksgiving now under our belts and the holiday season in full swing, a new diet that seems almost tailor-made for this time of year is making headlines.

Called the "short-term modified alternate-day fasting" diet in a recent study, it is known by other names, including the "feast-and-famine diet," and works like it sounds. On "famine" days, dieters eat 25 percent of their recommended intake of calories, while on "feast" days they are free to eat as much as they wish.

(For those who don't see the connection to Thanksgiving, another hint: If you were binge-eating on Black Friday, you were doing it wrong.)

The news on this comes on the heels of the publication of a U.S. government-funded clinical trial of the diet published in the American Journal of Clinical Nutrition.

For the study, 16 subjects (12 women and 4 men) were monitored for 10 weeks. They served as their own control group for the first two weeks, began dieting the next four weeks with their menus set and then were able to select their own foods for the final four weeks of the trial.

Researchers reported that dieters adhered for roughly 86 percent of the days and lost about one-and -a-half pounds a week during both the controlled diet and the self-selected diet. They also found that body fat dropped by a few percentage points, and cholesterol and blood pressure dropped slightly as well, concluding that the feast-and-famine diet may be an option to help obese people lose weight.

While our usual diet judge's panel was unavailable on this holiday week, our substitute judges were not ready to give this diet a thumbs up.

"It's unrealistic for most people. Most people wouldn't be able to keep that up," said Dr. Jana Klauer, a Manhattan physician and research fellow at the New York Obesity Research Center at St. Luke's-Roosevelt Hospital. "I wouldn't advise people that way."

Klauer said the size and length of the study were both too small for anyone to draw a conclusion.

"It should be a six-month study, and you would want an equal number of men and women, and you want larger numbers," she said. "Sixteen people doesn't tell you very much."

She also worried that the lack of consideration given to medications and exercise in the study might have affected the results -- attributing weight loss or weight gain to food, when really other factors were at work.

"I think that exercise must be part of anyone's lifestyle. Far too many people are sedentary," Klauer said.

And Connie Diekman, director of university nutrition at Washington University in St. Louis, worried that the diet would lead to binging that would not ultimately lead to weight loss.

"Everybody likes to save up calories with the anticipation that it will balance out, but the bottom line is when we go too long without eating or go without eating for too long, that instinct to eat kicks in and we don't have as much control over what we eat as we would like to," she said.

The feast-and-famine diet is only the most recent trendy diet to come onto our radar. In the past, the ABC News Medical Unit rounded up some of the most popular diets to date and subjected them to the scrutiny of nutrition experts Joanne Ikeda, cooperative extension nutrition education specialist and lecturer in the Nutritional Sciences Department at University of California, Berkeley; Dr. David Katz, co-founder and director of the Yale Prevention Research Center; and Keith-Thomas Ayoob, director of the nutrition clinic at the Albert Einstein College of Medicine.

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The following pages feature each of these diets, as well as whether you can count on them to help you achieve a healthier weight.

What It Is: The 4 Day Diet is the brainchild of Dr. Ian Smith, author and diet consultant for VH1's "Celebrity Fit Club," who found that people were not complying with their diet plans because they suffered from what he called "food boredom."

"People get tired of eating the same thing over and over again," Smith said. "This is a way to move the food around so people are eating good food and don't get tired of eating it because they know new foods are coming. ... Even if they were in a tough phase, they knew it would only last four days. From a psychological standpoint, that's a great boost."

Smith's plan is based on seven mix-and-match four-day-long modules that consist of a defined food group or plan. For example, the Induction module is meant to detoxify and cleanse the system, while the Protein Stretch module incorporates foods such as eggs, lean meat and vegetables; the Smooth module allows people to indulge in forbidden favorites such as pizza. Together with exercise, Smith said his modules keep the body from becoming accustomed to one diet plan.

Expert Verdict: Katz: "Obviously there is no science to back this up. The ultimate goal of 'dieting' should be to establish a stable, healthful dietary pattern; I see no hope whatsoever of that here. So this is all about, and only about, short-term weight loss -- which just about any diet can provide. ... What is the right answer? Learn to choose wholesome foods; learn to use them in wholesome meals; and make a lifelong commitment to healthful eating and regular activity that includes the other members of your household. That's the truth."

Ayoob: "This diet has some nice aspects to it, but balance isn't one of them. ... It's different each day, it's not boring. It encourages you to keep a food diary. It allows you an occasional indulgence so you don't feel deprived. Lots of fiber, fruits and veggies. I especially like that it includes beans -- a terrific food. [But] some dieters will find that they need at least some consistency. Lots of different calorie intakes over the four days; some are really low, some not."

Ikeda: "Like most diets, [this one] can result in weight loss. ... My big criticism of this diet is it does not teach people how to eat a healthy, well balanced, nutrient-dense diet that they can keep eating for the rest of their life. ... And I don't care how well one eats, if a person is not physically active, they are not going to be healthy."

What It Is: The Flat Belly Diet, launched by Prevention magazine editor-in-chief Liz Vaccariello, is built around a 1,600-calorie-per-day strategy that allows dieters to eat four meals per day selected from hundreds of meal possibilities.

Central to the diet is the principle that every meal must contain a source of MUFA, short for monounsaturated fatty acids. According to the diet's proponents, these predominantly nut-based oils can target-reduce dangerous belly fat. The diet also commences with a four-day jumpstart to get rid of abdominal bloating, during which a dieter drinks what the proponents of the diet call Sassy Water, a lemon- and ginger-containing beverage named after Prevention nutrition director Cynthia Sass.

And according to a small MRI imagine study released Monday out of the Yale University Prevention Research Center, the diet reduced visceral belly fat on average by 33 percent in 28 days for nine overweight women. Other risk factors, such as high cholesterol and blood pressure, were also reduced in the study participants.

Expert Verdict:

Katz: "[The diet is] generally healthful, with an emphasis on foods noted as being good for insulin resistance. My lab actually studied the effects of this short term, and they were quite good."

Ayoob: "You may have a flatter belly in 32 days but that's because you're losing weight, pure and simple. Make no mistake, your body will determine where you lose weight. It tends to come from the belly first anyway -- that's usually the body's first preference -- but it's the weight loss that's flattening your belly, not some diet miracle."

Ikeda: "This diet is based on the premise that a higher intake of monounsaturated fatty acids will result in a flat abdomen. There is nothing in the scientific literature that substantiates this claim. The best way to get a flat belly is to increase the strength of abdominal muscles by exercising them."

What It Is: The so-called full-fat diet builds off of research in January 2007 in which Swedish researchers found that women who had at least one serving of milk (whole milk, to be exact) or cheese each day experienced less weight gain over the following nine years than their counterparts who did not. Some concluded from this research that other full-fat daily foods may also provide these weight loss benefits, though the researchers behind the Swedish study were hesitant to delve so deeply into the results to make a similar claim.

While the full-fat diet has many different versions, one of the most prominent proponents of eating foods in their full-fat form is New York-based nutritionist Esther Bloom, who delivers such advice in her book, "Eat, Drink and Be Gorgeous."

Expert Verdict:

Ayoob: "I like the non-diet mentality of this. It's the idea that you can 'have your cake and eat it too.' But it's clear about this: You can't have it all the time and in all amounts. It's the idea that nothing is forbidden, and that's good."

Ikeda: "Although Esther Blum is an RD [registered dietitian], which gives her a plus for credibility in my book, her enthusiasm for supplements negates the plus with a minus. None of the endorsements on her Web site come from credible nutrition experts."

Katz: "I didn't find enough information about this to make a judgment, but the usual promises were made."

What It Is: The Atkins Diet was first popularized in 1972, with the release of the book "Dr. Atkins' New Diet Revolution." Controversial from the start, the diet is built around the idea that consuming too many carbohydrates is the main factor behind overweight and obesity. Therefore, by drastically reducing the intake of carbohydrates and shifting over to a diet high in protein in fat, a person can force his or her body to burn stored fat more efficiently.

The Atkins diet gained momentum at the beginning of the decade, and diet authors have published a host of new books aimed at further delving into the benefits of a low-carb approach to weight loss.

Expert Verdict:

Ikeda: "Is this old thing still around? If it worked, obesity would no longer be a problem in this country, since a good percentage of the population has tried it."

Katz: "I think this is a silly diet at odds with health. It restricts choice very severely, which in turn restricts calories severely -- so it, of course, produces short-term weight loss. But cutting out 'carbs' long term makes no sense; everything from lollipops to lentils is a 'carb,' so this diet throws out the baby with the bathwater."

Ayoob: "This is the original 'Full-Fat Diet.' Isn't America over this one yet? For people who plan to ditch their resolutions, this diet is for them -- people don't tend to stay with it very long. Just understand that when you finally let go of this diet, you'll have to go for something more realistic and not so limiting. Why not do that right from the start?"

What It Is: While there is no single Detox diet, all are built around the idea that, by eating or avoiding certain foods, you can cleanse -- or "detoxify" -- your body. The toxins that are purportedly eliminated from the body through these diets are most often identified as chemical pollutants from the environment, along with supposedly harmful byproducts of human metabolism that linger in the body's tissues. Most Detox diets are intended to be temporary, lasting a few days or a couple of weeks.

Detox diets also provide a constant source of fodder for celebrity magazines, as stars including Gwyneth Paltrow, Angelina Jolie and Beyonce Knowles have reportedly tried them in the past.

Expert Verdict:

Katz: "All Detox diets are rather silly. The body detoxes itself just fine. No real 'there' there."

Ikeda: "Doesn't anyone remember the lessons in human anatomy and how the body functions that were taught in elementary, middle school, and high school? Well, if one did remember, then one would realize that the body is self-cleansing -- like a self-cleansing oven. We get rid of 'toxins' daily in urine, feces and sweat. If we didn't, we would be dead in a matter of days."

Ayoob: "This one is temporary; it's meant to be temporary, and that's not going to be of much help to most people. Even temporarily -- several days to a week -- it's a bad idea. It's mostly about fruits, steamed veggies and not much protein at all. Bad idea. Stick to this diet strictly and you'll be losing muscle mass -- and that's your calorie engine. ... Detox diets may have been around for years, but so has fasting, and I wouldn't recommend that as a means of weight loss either. Period."

What It Is: The Zone Diet, developed by Dr. Barry Sears, purports to balance the body's hormone levels within a specific range by controlling the foods that are consumed. According to the official Web site for the diet, "The Zone Diet can best be described as a moderate-carbohydrate, moderate-protein, moderate fat diet that has approximately one gram of fat for every two grams of protein and three grams of carbohydrates."

The Zone Diet places special emphasis on the moderate intake of low-fat protein, low glycemic-load carbs (such as those found in fruits and vegetables), and monounsaturated fats, as well as all needed nutrients.

Expert Verdict:

Ayoob: "This one is fairly moderate, focusing on a good amount of lean protein, moderate fat and moderate carbs. Skip the vegetarian version if it's not your thing."

Katz: "I think this is too high in protein. It works by providing a strict dietary discipline, but suffers the same problem with sustainability as the others."

Ikeda: "Another oldie that had no impact whatsoever on the obesity epidemic in this country."

What It Is: The South Beach Diet, developed by cardiologist Dr. Arthur Agatston, is a three-phase plan intended to help adherents lose weight in the short term and keep it off long term. Of the three phases, the first is the most restrictive, especially when it comes to carbs. Dieters are instead encouraged to include lean protein and high-fiber vegetables in their meals. Phases 2 and 3 gradually reintroduce non-refined carbohydrates and other dietary elements.

The diet plan also encourages exercise as a part of the diet, a feature that proponents say distinguishes it as a healthy lifestyle rather than simply a diet.

Expert Verdict:

Ayoob: "This one is pretty moderate. Developed by a cardiologist, it's heart-healthy. It tends to penalize refined carbs. They're really OK; just watch portions and go for whole grains whenever you have the choice. It also focuses on exercise, and that's the other part of the diet puzzle. Activity -- you've got to have it, or the diet works a heck of a lot more slowly."

Katz: "Surprisingly silly and short on substance, given the size of the following: Cut out a lot of foods, add some back, then add some more back. At that point, if you start regaining weight, cut them all out again..."

Ikeda: "Where are the sequels? I'm waiting for the 'North Beach Diet,' the 'West Beach Diet' and the 'East Beach Diet.' Or perhaps we need an 'Any Old Beach Diet.'"

Joseph Brownstein contributed to this report.

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