The Promise

Could eating a diet based on your blood type -- O, A, B, or AB -- help you trim down and get healthier? That's the idea behind the Blood Type Diet, created by naturopath Peter J. D'Adamo.

D'Adamo claims that the foods you eat react chemically with your blood type. If you follow a diet designed for your blood type, your body will digest food more efficiently. You'll lose weight, have more energy, and help prevent disease.

Level of Effort: High

If you don't already know your blood type, you'll need to find that out. The results will determine exactly what you need to do.

Limitations: Depending on your blood type, you may need to severely restrict the foods you eat.

Cooking and shopping: Your blood type will determine your shopping list and your choices when eating out.

Packaged foods or meals? None required.

In-person meetings? No.

Exercise: The Blood Type Diet recommends exercises based on your blood type. For instance, it suggests yoga or tai chi for type As, and vigorous aerobic exercises like jogging or biking for up to an hour a day for type Os.

Does It Allow for Dietary Restrictions or Preferences?

Because the diet dictates that you eat very specific types of food based on your blood type, it doesn't allow much for personal tastes.

For example, if you're a big fan of meat and potatoes, you won't be very happy on the type A diet, which is mostly vegetarian.

There are even recommendations about the types of spices and condiments you can use.

If you're looking for a diet that's gluten-free, you should know that this diet doesn't ban gluten. You may be able to make choices that are gluten-free, if you read food labels carefully.

What Else You Should Know

Cost: D'Adamo recommends a lot of specialty and organic foods (such as soy milk and carob chip cookies), which can be pricey. Vitamin and herbal supplements are also part of the diet.

Support: You do this diet on your own.

Does It Work?

One study found that adults eating the type A diet showed improved health markers, but this occurred in everyone, not just those with type A blood type. In 2013, a major review concluded that no evidence exists to support benefits of blood type diets.

It's likely that you would lose weight, though, because the diet can be very restrictive.

Is It Good for Certain Conditions?

The Blood Type Diet makes recommendations based solely on your blood type. So, if you have a chronic condition (say, diabetes), you may be told to eat high protein, while another person with diabetes may have to avoid dairy or chicken. This may conflict with your diabetes treatment plan.

The American Diabetes Association recommends a more practical approach to your day-to-day eating. It also cautions against focusing on specific foods. In most cases it doesn't recommend cutting out any major food groups.

The Blood Type Diet also fails to address other conditions such as heart disease, high blood pressure, or cholesterol. Any needed weight loss is sure to have a positive impact on these conditions. But no matter your blood type, you should follow the same guidelines issued by The American Heart Association (AHA) for a low-fat and low-salt diet.

Also, everyone should aim for 150 minutes of aerobic exercise per week and at least 2 days of strength training per week.

The Final Word

On The Blood Type Diet, youll avoid processed food and simple carbs. That may be enough to help you lose some weight. But any weight loss on this diet has not been linked to your blood type.

Theres also no research proving that this diet can aid in digestion or give you more energy.

Although you'll buy and prepare your own foods on this plan, your choices are limited depending on your blood type. So be prepared to spend some time in the kitchen.

The diet may quickly become expensive, too, since the author recommends you buy organics as well as his own line of supplements.

If the Blood Type Diet intrigues you, consider this: The science is stacked behind traditional recommendations for healthy eating for weight loss -- not restrictions based on the type of your blood.