Can the Flat Belly Diet Really Zap Your Belly Fat? may earn compensation through affiliate links in this story.
The Flat Belly Diet promises to help you lose up to 15 pounds in a month by changing your eating habits.
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If you're trying to lose weight and have searched high and low for the best way, you may have stumbled across the Flat Belly Diet. A name like the Flat Belly Diet conjures up a visual many of us aspire to — and the promise of losing up to 15 pounds in 32 days only adds to the intrigue.

But then there's the million dollar question: Does it really work, and is it safe?


Here's our review of the diet, covering the premise of the plan, what you can (and cannot) eat and whether it'll really help with weight loss, so you can decide if it's worth your time.

So, What Is the Flat Belly Diet?

The Flat Belly Diet was created by ​Prevention​ magazine and debuted in 2008 with the release of the book ​Flat Belly Diet!​ Since then, various extensions of the book have been published, including a ​Flat Belly Diet! Pocket Guide,​ numerous cookbooks, ​Flat Belly Diet! Diabetes​, ​Flat Belly Diet! For Men​ and so on.


The diet promises that you will lose up to 15 pounds in just 32 days. The 32 days comes from the two phases of the diet:

  • The 4-Day Anti-Bloat Jumpstart:​ This phase focuses on reducing water retention, gas and constipation by eating 1,200 calories a day — predominately fruits, vegetables, whole grains and a proprietary water recipe. It's recommended that you avoid high-sodium foods and beverages.
  • The 4-Week Meal Plan:​ Built on a 1,600-calorie diet broken up into four, 400-calorie meals as well as one 400-calorie "snack pack." It's recommended that you don't go more than four hours between eating.


The premise of the diet is focused on one unique nutrient — monounsaturated fats (MUFAs) — because growing research at the time showed this fatty acid may play a role in reducing belly fat. Monounsaturated fats are built into every meal on the Flat Belly Diet plan so that they're consumed throughout the day. Exercise is optional on the Flat Belly Diet.

It is worth noting that the diet is no longer maintained by its creators (in other words, the plan hasn't been updated in more than a decade), but the Flat Belly Diet! line of books and resources are still available for sale.


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What You Can (and Can’t) Eat on the Flat Belly Diet Plan

Flat Belly Diet foods are loosely based on the Mediterranean diet.
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The diet is focused on eating MUFAs throughout the day, so foods rich in these fats make up a large portion of the diet. Here's a breakdown of what's allowed and what you should avoid on the Flat Belly Diet.

Foods Allowed

  • Olive oil
  • Avocados
  • Nuts and seeds
  • Dark chocolate
  • Soybeans
  • Plant-based oils
  • Fruit and some vegetables
  • Whole grains
  • Lean meats and proteins

Foods to Avoid

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Does It Work for Weight Loss?

The Flat Belly Diet may help you lose weight, but it's not likely that you'll keep it off.
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The short answer is yes. The diet is a four-day 1,200-calorie and four-week 1,600-calorie meal plan based on predominately whole foods, so if your daily calorie needs are above this amount, you will lose weight on this plan.

With that said, there's nothing inherently unique about this diet compared to most other calorie-restricted programs. While monounsaturated fats are healthy, they are not a magical nutrient that will help you shed weight — especially the suggested 15 pounds in 32 days. This is difficult for most of us to do, with or without an exercise program.

Wondering how to calculate your calories for weight loss? Download the MyPlate app to do the job and help you track your intake, so you can stay focused and achieve your goals!

Is the Flat Belly Diet Safe?

The Pros

1.​ The diet is loosely based on the Mediterranean diet, which is backed by decades of research and is ranked the No. 1 Best Diet Overall by U.S. News & World Report. The diet focuses on eating whole, nutrient-dense foods with a particular emphasis on eating healthy monounsaturated fats.

2.​ It also promotes a consistent eating schedule and doesn't require you to buy specific brand foods like some other diet programs, and it doesn't require the use of supplements.

3.​ Plus, the eating plan is generally low in saturated fats and sodium, making it heart-healthy.

The Cons

1.​ The diet is pretty regimented, so it's not appropriate for most people with a history of disordered eating and/or an eating disorder.

2.​ The promised results of losing "up to 15 pounds in 32 days" are likely overstated. In fact, as detailed in the forward by David Katz, MD, a small study on the diet was conducted by Dr. Katz and his team. While the women in the study did lose a significant amount of weight, the average weight loss was only 8.5 pounds.

3.​ It's worth noting that there's no other research on this specific diet's effectiveness for weight loss, and Dr. Katz's study didn't follow up with the participants to see if they were able to keep the weight off in the long run. It's unlikely that the diet leads to sustainable weight loss, though — once you start eating normally again, the weight you lost will likely return.

4.​ Because of the timing of the meals, if you have diabetes, you should work with a dietitian to determine if the diet meets your personal needs.

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A Healthier Approach

Adopt a Mediterranean diet:​ A smarter tactic for weight loss and overall health may be to implement the Mediterranean diet and way of eating, and to ditch the regimented and calorie-restricted meals and snacks.

Avoid processed foods:​ By filling up on nutritious, whole foods, you'll have less room for highly processed foods (think: chips, crackers, sweets), which can add to weight gain.

In fact, researchers in a May 2019 clinical trial published in ​Cell Metabolism​ found that when they broke subjects into two groups (those who ate ultra-processed foods versus those who ate an unprocessed diet), the unprocessed group ate about 500 fewer calories each day, despite having access to the same amount of food (matched for calories and macros). Those on the unprocessed plan lost a pound over the course of two weeks while the ultra-processed group ​gained​ a pound.