The Promise

Eat fat and lose weight. That's the promise of the Flat Belly Diet.

Now for the fine print: The kind of fat matters. The plan focuses on monounsaturated fats, which you get from olive oil, nuts, and other plant foods.

Authors Liz Vaccariello and Cynthia Sass, MPH, RD, claim that in 32 days, you can lose up to 15 pounds and drop belly fat by following their plan:

Eat 400 calories per meal, four times per day (daily total: 1,600).

Dont go longer than 4 hours without eating.

Eat monounsaturated fats at every meal.

What You Can Eat and What You Can't

First, you target bloating for four days, aiming at consuming 1,200 calories each day. During that time, you can't add salt to any food and you must avoid:

Processed foods

Foods that can make you gassy, like beans, broccoli, and onions

Carbs like pasta, bananas, and bagels

You must also drink 2 liters of water mixed with ginger root, cucumber, lemon, and mint leaves, which the book calls "sassy water."

After that, you eat a Mediterranean-style diet for 4 weeks with 1,600 calories per day. The menu includes items like Greek Lemon Chicken and Pumpkin Maple Cheesecake.

Level of Effort: Medium

The diet loosens up a little after 4 days. You'll still need to eat often and include monounsaturated fats, and hit the calorie mark precisely every day.

Limitations: The first 4 days are very restrictive. After that, you must eat 400 calories every 4 hours and include monounsaturated fats with every meal. A busy or unpredictable schedule can make this challenging.

Cooking and shopping: The diet includes recipes, ideas for snacks, and tips for ordering fast food.

Packaged foods or meals? Certain brands of food are recommended but not required.

In-person meetings? No.

Exercise: It's not required. But the book includes a flat belly workout to support the diet.

Does It Allow for Dietary Restrictions or Preferences?

Vegetarians and vegans: The plan suggests substitutions that work for these diets.

Low-salt diet: You're not supposed to add salt to anything you cook. You still need to check the label on other foods to see how much sodium they have.

Low-fat diet: This is not a low-fat diet, but the type of fat is heart-healthy. You eat monounsaturated fats at every meal, and you need to watch your portion sizes so you don't get too many calories.

What Else You Should Know

Cost: None except your groceries. Olive oil, nuts, and avocados may add to your bill. You could save by cutting back on other foods that the diet doesn't emphasize.

Support: You do this diet on your own.

Chances are if you eat just 1,600 calories a day, youre going to lose weight. But losing 15 pounds in 32 days is a huge stretch.

To do that and lose fat (not water weight), youd have to cut about 1,600 calories out of your diet every day! You could do that by eating less and increasing your exercise, but thats a lot to ask of anyone.

Theres also nothing magical about the diet thats going to lead to a flat belly. Monounsaturated fats dont have any special effect on belly fat. Any diet that cuts calories and leads to weight loss will slim your belly along with the rest of you.

The diet also recommends you cut back on high-fiber foods like beans and broccoli. Yes, they may cause gas -- maybe even a bit of temporary bloating if youre not used to them. But these foods are great ways to lose weight and keep it off. Fiber helps you feel full, so you eat less.

If this diet ultimately gets you to follow the Mediterranean diet, then its a good thing. Thats a winning strategy and one that has been linked to weight loss in multiple medical studies.

Is It Good for Certain Conditions?

Removing saturated fat (the kind found most often in animal products like meat) and replacing it with monounsaturated fat in moderation is undoubtedly a good thing. It helps lower LDL bad cholesterol and the chance of heart attack and stroke. So its a good approach for anyone with diabetes, high blood pressure, high cholesterol, or heart disease.

The aggressive weight loss the plan promises is concerning, and there isn't flexibility on calories. If you have diabetes, you should attempt this diet only under the care of your doctor. Youll need to work closely together to monitor your blood sugar and adjust your meds, so your blood sugar doesnt fall too low.

The Final Word

If youre not ready for a huge change in your diet, look elsewhere for weight loss. The extreme cut in calories in this diet is more likely to leave you discouraged instead of thinner. If you think you have it in you, go for it. Just have a plan in place for sticking with a more moderate weight loss plan in the long run.