The Flat Belly Diet is written by two editors from Prevention magazine. Liz Vaccariello and Cynthia Sass have modeled their diet around a traditional Mediterranean diet.

The book is available for $25.95 . There is also a cookbook for $27.95.

The diet claims that - not only will the scales go down - but “[...] it targets the second type of fat–visceral–which is much more dangerous and difficult to lose”.

Diet Basics

The Flat Belly Diet is based on monounsaturated fats (also called MUFA: Monounsaturated Fatty Acids). Every meal should have a MUFA component (that ideally replaces the saturated fat content).

Meal plans are set at 1600 Calories per day.

Recommended Foods Containing MUFAs

Oils: Canola oil, flaxseed oil, olive oil, peanut oil, pesto sauce, safflower oil, sesame oil, soybean oil, sunflower oil, walnut oil.
Nuts and Seeds: Almonds, almond butter, Brazil nuts, cashew butter, chunky natural peanut butter, dry-roasted cashews, dry-roasted peanuts, dry-roasted sunflower seeds, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios, roasted pumpkin seeds, smooth natural peanut butter, sunflower seeds, sunflower seed butter, tahini (sesame seed paste), walnuts.
Olives
Dark Chocolate

The rest of the diet is very similar to a Mediterranean diet:

Fruit (in season)
Vegetables (in season)
Whole grains
Limited red meat intake

Exercise

The program recommends exercise - and provides a series of cardio workouts, and full body resistance training exercises. However the marketing of the diet claims “no exercise required”.

Overall

The marketing claims surrounding the Flat Belly Diet are excessive at best, and false at worse. Example: Targets unhealthy belly fat first!, Lose up to 7 lbs and 5 3/4 inches in just 96 hours!, Zero Exercise Required! Eat the foods you love and never go hungry.

This market-speak is simply designed to sell product - without any firm evidence to back it up.

However, there is research backing up the claims made about MUFAs. In a number of studies it has been shown that replacing saturated fats in the diet with monounsaturated fats results in a small weight loss, and an improved cholesterol profile.

Provided the marketing material is not taken too seriously, this is a healthy diet, and, when followed will probably result in weight loss. The claim that it will specifically target visceral belly fat seems to have little basis in research however.

References

Substitution of saturated with monounsaturated fat in a 4-week diet affects body weight and composition of overweight and obese men, British Journal of Nutrition, Vol 90 Issue 3 Sep 2003. Piers et al.
Cholesterol reduction using manufactured foods high in monounsaturated fatty acids: a randomized crossover study, British Journal of Nutrition, Vol 81 Issue 6 Jun 1999. Williams et al.