What Is the Flat Belly Diet?

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

While the eating plan is based on sound nutritional concepts, it may overpromise in terms of results.

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

Background

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

Since that time, other related books have been published including Flat Belly Diet for Men, Flat Belly Yoga, Flat Belly Diet Pocket Guide, and several Flat Belly cookbooks.

A later edition of the book also includes a foreword by David Katz, M.D. who at the time was an associate professor adjunct of public health at Yale University School of Medicine. Katz and his colleagues at Yale-Griffin Prevention Research Center conducted a research study based on the eating program. The results of the study are outlined in the foreword.

The diet gained popularity and media attention immediately upon publication due in part to the substantial media platform offered by the author's roles at Prevention. But also because it claims to target the belly—a body part that many consumers struggle with.

Belly fat is a concern for both men and women, not only for aesthetic purposes but also for health reasons. Technically known as visceral fat, this type of belly 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 has indicated that visceral fat may increase over 200 percent in men and 400 percent in women between their 30s and 70s.

It is important to note that there are other diet programs that include the words "flat belly." Most of these are diet programs promoted online. These weight loss plans are different than the diet outlined in the books by Vaccariello and Sass. Additionally, the original website that promoted the diet (flatbellydiet.com) is no longer available.

How It Works

The Flat Belly diet lasts 32 days. It includes a four-day jumpstart during which you consume 1,200 calories per day. The jumpstart is designed to reduce bloating, according to the authors. Vaccariello has said in interviews that test subjects lost up to seven pounds during these first four days.

After that, you follow an eating plan that requires you to adhere to three rules.

  • Consume 1600 calories per day by eating four 400-calorie meals
  • Include monounsaturated fats at every meal
  • Never go for more than four hours without eating

According to the program, you can lose up to 15 pounds if you follow these rules for the duration of the diet.

What to Eat

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

Because you must eat monounsaturated fats at each meal, you'll need to learn about and consume foods that are rich in the fatty acids, also known as MUFAs.

In order to reduce bloating, especially during the initial phase of the program, people who follow the diet are encouraged to consume cooked rather than raw vegetables and to reduce their intake of sodium-rich foods.

Compliant Foods (Examples)

  • Avocados

  • Olive oil

  • Nuts and seeds

  • Soybeans

  • Some fruits and vegetables

  • Dark chocolate

Non-Compliant Foods (Examples)

  • Processed foods

  • Refined carbohydrates

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

  • Citrus fruits

  • Salty foods

Avocado, 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 also satisfying to consume and may help you to avoid less healthy salty or fatty foods.

Plant-based oils are another good source of the 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 another good source of monounsaturated fats 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, 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 program.

Recommended Timing

If you go on the Flat Belly Diet, you will eat four meals each day. This is a departure from tradition for many people who are used to eating three meals each day. However, the diet's authors advise that you should never go for more than four hours without eating.

The advice to eat regularly throughout the day is consistent with mainstream nutritional thinking when the book was published. Many nutrition experts recommended a "grazing" approach to weight loss or weight maintenance because it was believed that if you avoided severe hunger you would avoid overeating at mealtime.

However, some studies have suggested that an increase in eating occasions also increases total daily caloric intake, which can lead to weight gain or a lack of weight loss results.

Resources and Tips

There are no required foods or products that you need to buy in order to follow this diet. However, there are a number of cookbooks that many consumers may want to invest in if they plan to stay on the program long-term.

When the program was first introduced, consumers had a choice of buying the book or searching for recipes and tips online. There was a subscription website that provided subscribers with the information needed to follow the diet. In addition, many resources (such as recipes, food swaps, and other tips) were provided on Prevention's website.

However, the subscription website is no longer available and many of the resources are no longer available at Prevention's website.

Modifications

Since the program was first introduced, there have been variations to the original Flat Belly Diet book.

The Flat Belly Diet Diabetes is for people who want to manage diabetes or reduce blood sugar. The book, written by Liz Vaccariello, Gillian Arathuzik, and Steven V. Edelman M.D., outlines a diabetes-friendly eating plan that lasts five weeks long. Like the original diet, it focuses on monounsaturated fat foods.

The Flat Belly Diet For Men is written by Liz Vaccariello and Milton Stokes. The program differs from the original plan in that it allows for five meals per day (instead of four) and promises to help men lose up to 11 pounds during the kickstart phase and up to 27.2 pounds during the rest of the four-week plan.

Pros and Cons

Pros

  • Encourages consumption of healthy fats

  • Allows for 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

Healthy Fats

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.

Regular Eating

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 over the long-term.

Weight Loss

The prescribed caloric intake (1,200 in the first phase and 1,600 in the next phase) are in line with calorie goals for many well-regarded weight loss plans. Since many people consume about 2,000 calories per day or more, a 400-600 calorie deficit is likely to result in weight loss.

Nutritious Food

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. In fact, scientific studies have shown that plant-based eating is associated with a reduced risk of disease and obesity.

Inexpensive

There are no products or subscriptions to purchase on this plan. The book is inexpensive, and depending on your shopping habits, many of the foods can be inexpensive to purchase.

Cons

Lack of Resources

Since the diet is no longer actively promoted online, consumers wishing to follow the plan must buy the book. For some, reading the book and keeping it on hand may not be convenient.

Overpromises Weight Loss

The weight loss claims associated with this program are substantial. In general, losing 1-2 pounds of weight per week is considered reasonable. The promise of a 15-pound weight loss in 32 days means that you would have to lose 1-2 pounds per day. If you were able to lose that amount of weight, most it would come from water loss, not fat loss.

Results Not Sustainable

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

Inconvenient and Expensive

Some foods like nuts and olive oil are pricey. Additionally, not everyone has regular access to these foods. Additionally, busy people or those with structured jobs may have a hard time adhering to the four-meal-per-day schedule.

How It Compares

The Flat Belly Diet book is 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 flat belly program and the Mediterranean diet is that on the flat belly diet you avoid legumes because they can cause gassiness and bloating. Also, the Mediterranean diet does not require any specific eating schedule or calorie intake.

The 2019 U.S. News and World Report Best Diets ranks the Flat Belly Diet number 15 in Best Diets Overall and gives it an overall score of 3.3/5.

USDA Recommendations

In many ways, the flat belly diet is also consistent with USDA guidelines for healthy eating. The calorie guidelines encouraged foods, and foods to avoid are in line with recommendations provided by the MyPlate program.

During the first, more restrictive, phase your intake of vegetables and whole grains may be limited when you follow the plan, but for the duration of the flat belly diet, all of the main food groups are accounted for on the program.

While the 1,200 and 1,600 calorie goals are likely to produce weight loss for most people, most sources recommend that you determine a calorie goal based on your age, gender, and activity level. Some people who are very active may need more calories.

A Word From Verywell

While the Flat Belly Diet books were very popular when they came out, their influence is fading. 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 that you will see results. However, you will need to determine a long-term strategy to keep the pounds from coming back. Switching to the Mediterranean diet may be a smart option.

Another option is simply to go on the Mediterranean diet to begin with and adopt it as a long-term program for healthy eating. The focus on healthy fats, whole foods, and plant-based eating on both programs is smart for weight loss, weight maintenance, and overall wellness.

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