What Is the Flat Belly Diet?

flat belly diet

Verywell / Debbie Burkhoff

At Verywell, we believe there is no one-size-fits-all approach to a healthy lifestyle. Successful eating plans need to be individualized and take the whole person into consideration. Prior to starting a new diet plan, consult with your health care provider or a registered dietitian, especially if you have an underlying health condition.

The Flat Belly Diet is an eating plan that claims you can lose 15 pounds in 32 days by following a food program centered on healthy monounsaturated fats. Those interested in trying the eating plan can buy the original "Flat Belly Diet" book, the pocket guide, or any of the accompanying Flat Belly cookbooks to learn the program.

The Flat Belly Diet was developed by Liz Vaccariello, the former editor-in-chief of Prevention magazine, and Cynthia Sass, MPH, RD, a nutrition consultant and wellness expert. The original diet book was published in 2008 when both authors were affiliated with the magazine.

A later edition of the book includes a foreword by David Katz, MD, who at the time was an associate adjunct professor of public health at Yale University School of Medicine. Katz and his colleagues conducted a research study based on the Flat Belly Diet plan. The results of the study are outlined in the foreword.

Keep in mind that many diet programs include the words "flat belly," but these weight loss plans are not the same as the Flat Belly Diet. While the Flat Belly Diet is based on sound nutritional advice such as eating plenty of healthy fats, it may overpromise in terms of results. It may also send the wrong message about body image.

What Experts Say

"The Flat Belly diet emphasizes monounsaturated fats and a calorie-controlled meal plan for weight loss. The meals are nutritious and you’ll probably see some weight loss on this diet—but experts agree it’s unlikely you’ll lose 15 pounds in 32 days, as the plan suggests."
Chrissy Carroll, RD, MPH

What Can You Eat?

The Flat Belly Diet is often compared to the Mediterranean diet and follows many of the same eating guidelines. On the Flat Belly Diet, however, there is a particular focus on monounsaturated fats, also known as MUFAs.

You'll eat MUFAs at every meal while you're on the program, so you'll need to learn about the foods that contain these fatty acids. Foods high in MUFAs include avocados, nuts and seeds, soybeans, some fruits and vegetables, and dark chocolate. 

What You Need to Know

The Flat Belly diet lasts 32 days. It includes a four-day jumpstart during which you consume a low-calorie diet of 1,200 calories per day. The jumpstart is designed to reduce bloating, according to the diet's creators. You will also eat four meals each day, which is a departure for those who are accustomed to eating three meals a day. You should also never go more than four hours without eating.

After the four days, you follow an eating plan that requires you to adhere to three rules:

  • Consume 1,600 calories per day by eating four 400-calorie meals
  • Include monounsaturated fats at every meal
  • Eat every four hours

There are no required foods or products that you need to buy in order to follow the Flat Belly Diet. In order to reduce bloating, especially during the initial phase, people who follow the program are encouraged to consume cooked rather than raw vegetables and to reduce their intake of sodium-rich foods.

The advice to eat regularly throughout the day is consistent with nutritional guidance. Many nutrition experts recommended a "grazing" approach to weight loss or weight maintenance because of the idea that if you avoid severe hunger you would avoid overeating at mealtime. But of course, this rule does not apply to everyone.

What to Eat
  • Avocados

  • Olive oil

  • Nuts and seeds

  • Soybeans

  • Some fruits and vegetables

  • Dark chocolate

What Not to Eat
  • Processed foods

  • Refined carbohydrates

  • Gassy foods including legumes, cauliflower, broccoli, Brussels sprouts, cabbage, onions, and peppers

  • Citrus fruits

  • Salty foods

Avocados, Olives, Plant-Based Oils

Foods like avocados and olives are high in monounsaturated fats. One avocado, for example, provides over 13 grams of monounsaturated fat. A small serving of olives provides about three grams of MUFAs. These savory foods are satiating, which may help you avoid less healthy salty or fatty foods.

Plant-based oils are another good source of healthy fat. One tablespoon of olive oil provides ten grams of monounsaturated fat. Other oils high in monounsaturated fats include canola oil, sunflower oil, and sesame oil.

Nuts and Seeds

Nuts and seeds are good sources of MUFAs that are quick and easy to consume. They contain antioxidants to help repair cell damage in the body, may help prevent diabetes, and may even have anti-inflammatory properties.

Soybeans

Soybeans like edamame can be a healthy addition to a meal or a snack on their own. The legume provides both monounsaturated and polyunsaturated fat.

Fruits and Vegetables

While the program encourages the consumption of fruits and vegetables, there are some caveats that are unique to the diet. For example, since the goal of the diet (especially the first four days) is to reduce belly bloat, people are encouraged to consume less gassy vegetables and to cook them before eating them. Additionally, citrus fruits are to be avoided because they cause gas.

Dark Chocolate

People who are on the diet and need a sweet treat are encouraged to consume dark chocolate. One ounce of the treat provides about 3.6 grams of monounsaturated fat.

Refined Grains and Other Processed Foods

Foods like white bread, cookies, and commercially produced muffins often contain saturated fat and very little or no monounsaturated fat. Refined grains provide less nutrition than whole grains and are likely to be higher in sugar and salt.

Salty Foods

Your sodium intake will have a big impact on bloating and water retention throughout the body. For that reason, (and because high sodium intake is not healthy) consumption of salty foods is not advised on the Flat Belly Diet.

Pros and Cons

Pros
  • Encourages consumption of healthy fats

  • Allows for a regular eating schedule

  • Is likely to result in weight loss

  • Promotes nutritious foods

  • Exercise is encouraged

  • Can be inexpensive

Cons
  • Few resources available other than the book

  • Overpromises weight loss

  • Results may not be sustainable

  • Some recommended foods can be expensive

  • May be inconvenient for some

Pros

People on the Flat Belly Diet are encouraged to eat plant-based foods, whole foods (such as fruits, veggies, nuts, and seeds), and foods that are known to be high in nutrition. There are no products or subscriptions to purchase on the plan, and the book is inexpensive. Depending on your shopping habits, some of the foods can be inexpensive to purchase.

The prescribed caloric intake (1,200 in the first phase and 1,600 in the next phase) is in line with calorie goals for many weight loss plans.

For many people, eating on a regular basis helps them to avoid overeating at mealtime or bingeing on junk food. And, for some, a regular meal schedule makes the diet easier to maintain.


Monounsaturated fats not only help develop and maintain your cells, but they also can help lower your LDL cholesterol levels, according to the National Institutes of Health. Keeping your LDL level low reduces your risk for heart disease and stroke.

Cons

Since the diet is no longer actively promoted online, consumers who wish to follow the plan will have to buy the book to learn the tenets. For some, reading the book and keeping it on hand may not be convenient.

Some foods like nuts and olive oil can be pricey, and not everyone has regular access to all of the recommended foods on the plan. Busy people or those with structured jobs may not be able to find the time to adhere to a four-meal-per-day schedule.

Additionally, the weight-loss claims associated with this program are substantial. Rapid weight loss is usually water weight. In general, losing 1 to 2 pounds of weight per week is considered reasonable and sustainable.

If you lose weight from water loss, the weight is likely to come back when you put certain foods back into your diet and resume your normal eating habits.

Is the Flat Belly Diet a Healthy Choice for You?

The U.S. Department of Agriculture 2020–2025 Dietary Guidelines for Americans recommends consuming nutrient-dense foods and beverages while staying within the recommended limit of 2,000 calories a day for weight management. The USDA also advises limiting foods and beverages with higher amounts of added sugars, saturated fat, and sodium, and also limiting the consumption of alcoholic beverages.

During the first, more restrictive, phase of the Flat Belly Diet, your intake of vegetables and whole grains is limited if you follow the plan closely, which does not adhere to federal dietary guidelines. But for the remainder of the diet, all of the main food groups are accounted for, despite the exclusion of some specific foods.

The Flat Belly Diet is also comparable to other eating programs and weight loss plans that focus on healthy fats, such as the Mediterranean diet. On the Mediterranean diet, you consume foods such as olives, olive oil, whole grains, fish, vegetables, fruit, nuts, seeds, and legumes. You typically avoid red meat, processed foods, and other sources of saturated fats.

The main difference between the two diets is that on the Flat Belly diet you avoid legumes and starchy vegetables because they can cause gas and bloat. Also, the Mediterranean diet does not require any specific eating schedule or calorie intake.

While the 1,200 and 1,600 calorie goals are likely to produce weight loss for most people, this range can vary based on your age, sex, and activity level. Some people who are very active may need more calories. Use this calculator to determine the right number of calories to meet your goal.

In some ways, the Flat Belly diet is consistent with federal guidelines for healthy eating. But it is not recommended as a weight loss plan since any weight loss experienced on the diet is likely water weight. It also excludes healthy foods like starchy vegetables and legumes which can be part of a balanced diet.

Health Benefits

Belly fat is a concern for both men and women, not just for aesthetic purposes but also for health reasons. Technically known as visceral fat, this type of fat surrounds the organs and can put you at risk for heart disease, type 2 diabetes, and certain cancers if it is too high.

Visceral fat is also known to increase with age. Research indicates that visceral fat may increase as much as 200% in men and 400% in women between their 30s and 70s. Since many people consume about 2,000 calories per day or more, a 400–600 calorie deficit on the Flat Belly Diet is likely to result in weight loss.

The diet also encourages the consumption of plant-based monounsaturated fats which have been linked to a reduced risk for cardiovascular disease. And in general, eating more plant-based foods can improve overall health. Studies show that plant-based eating is associated with a reduced risk of chronic disease and obesity.

Health Risks

While there are no known health risks associated with the Flat Belly Diet, some research has suggested that an increase in the frequency of meals can also increase total daily caloric intake, which could lead to weight gain or a lack of weight loss results.

Additionally, the promise of a 15-pound weight loss in 32 days is unrealistic. A healthy rate of weight loss is typically 1 to 2 pounds per week. Losing more than that would mostly come from water loss, not fat loss, which is not sustainable and not a healthy plan to support long-term weight management.

A Word From Verywell

While the Flat Belly Diet books were very popular when they came out, their influence is fading from the mainstream. It has become harder to follow the diet simply because fewer resources are available. If you choose to buy the books and follow the program, it is likely you will see some short-term weight loss results. However, you will need to determine a sustainable strategy for weight management.

You might consider the Mediterranean diet as a long-term eating plan. The focus on good fats, whole foods, and plant-based eating makes this lifestyle a healthy choice for weight loss, weight maintenance, and overall wellness.

Remember, following a long-term or short-term diet may not be necessary for you and many diets out there simply don’t work, especially long-term. While we do not endorse fad diet trends or unsustainable weight loss methods, we present the facts so you can make an informed decision that works best for your nutritional needs, genetic blueprint, and budget, and goals.

If your goal is weight loss, remember that losing weight isn’t necessarily the same as being your healthiest self, and there are many other ways to pursue health. Exercise, sleep, and other lifestyle factors also play a major role in your overall health. The best diet is always the one that is balanced and fits your lifestyle.

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Article Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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