There are four blood types — A, B, AB, and O. The theory is, if you’ve got type A blood, your nutritional needs are different from someone with type O blood and you need to adapt your diet to help with weight loss and protect your heart.
Research sparked by the blood-type plan — made famous by the book “Eat Right for Your Type,” published in 1996 — suggested it didn't help with weight loss. Rather, all the different plans, which are supposed to be personalized for each different blood type, reduced calories and they were all based on an abundance of fruit and vegetables, heart-healthy proteins and moderate fat.
"While we all want a personalized approach to weight loss, there's no solid evidence that 'eating for your blood type' is the way to go," said Madelyn Fernstrom, NBC News Health and Nutrition Editor.
A 2014 study from the University of Toronto did not find any association between the four blood types and health markers.
"The way an individual responds to any one of these diets has absolutely nothing to do with their blood type and has everything to do with their ability to stick to a sensible vegetarian or low-carbohydrate diet," said Dr. Ahmed El-Sohemy, the senior author of the study, in a statement.
"We can now be confident in saying that the blood type diet hypothesis is false."
A total of 1,455 healthy research participants were studied. They received their blood type assignment and baseline measure of health markers. Volunteers followed the specific diet assigned for that specific blood type, based on the book’s eating plan. They kept detailed food frequency questionnaires for one month, and weight and health markers were repeated.
While the dieters did lose weight, and improved their blood pressure, cholesterol, and triglycerides, there was no association found linking these changes to a specific blood type.
The bottom line? These data support that choosing any of these eating plans, independent of blood type, will promote good health. While the blood type theory might sound reasonable, the science does not support it.
"From a nutritional point of view, all four of these plans are very similar — balanced in both nutrients and calories — so choose whichever blood type plan appeals to you," Fernstrom said.
As with any diet plan, choose one that you feel you can stick with for the long run. Make sure it is nutritionally sound and contains the foundation of healthy eating (with smaller portions for weight loss):
- Rich in fruit and vegetables as the main source of carbohydrates
- Moderate amounts of heart-healthy fats
- Lean proteins from both animal and plant sources
- Limited amounts of fiber-rich starchy carbohydrates (bread, rice, pasta, cereals)
The good news is that there are many ways to eat less and move more for both good health and weight loss.
- My weight-loss journey: Inspiring stories of people who successfully slimmed down
- Why breakfast should be the biggest meal of the day
- A day of meals on the keto diet: Easy high-fat, low-carb recipes
A. Pawlowski contributed to this report.