What science says about Blood Type Diet For Weight Loss

Different medical doctors and health experts have conflicting views on the blood type diet, and many of them question the diet’s validity and effectiveness in treating or preventing obesity.

Supporters of this diet claim that lectins in food affect people’s health because each blood type reacts to lectins differently. Lectins might be beneficial, neutral, or harmful, depending on a person’s blood type. They suggest that if people restrict the foods that contain lectins harmful to their bodies, they can prevent or reduce the risk of obesity or weight gain.

On the other hand, most doctors do not believe that the blood type diet can affect an individual’s health. They claim that although specific lectins react with certain blood types and cause agglutination, most lectins interact in the same way with all blood types. Therefore, the hypothesis behind the diet is false. 

Plus, most foods do not contain significant amounts of lectins. Legumes are the only food group that has large amounts of lectins, and most of them are destroyed during cooking. Therefore, there is no need for people to avoid eating certain foods that contain lectins.

Furthermore, scientists cannot find sufficient evidence to back up the claims that dietary changes based on blood type are beneficial. They argue that most studies analyzing the effects of the blood type diet have been poorly designed. As a result, scientists do not know whether people’s health improved because of the blood type diet or because of the healthy foods that this diet recommends.

In addition, recent studies show that obesity is not correlated to blood type, contrary to what D’Adamo claims, so the blood type diet does not reduce or prevent obesity.

However, most doctors agree that this diet might be helpful because it promotes healthier eating habits, like eating fresh fruits and vegetables. Therefore, the diet might be useful because it is a healthy diet that avoids processed foods and sugar but not because each blood type does not eat specific types of food.

Some doctors also believe that the blood type diet might help with weight loss because it is very restrictive and eliminates certain food groups for different blood types. So, people consume fewer calories while on the blood type diet, leading them to lose weight.

Opinion in favor of Blood Type Diet for Weight Loss

Supporters of the blood type diet claim that the diet is effective because it recognizes that people have different nutritional needs based on their blood type. Individuals with different blood types react differently to lectins in certain food groups. Therefore, they need to restrict food groups that contain harmful lectins to remain healthy.

Proponents of the diet argue that there is no one-size-fits-all diet. That is why some people might try a diet and get great results, but when others try the same diet, they get very different results. According to the diet’s supporters, people’s results differ because the same food can have different effects on different blood types. That is why people need a specific diet based on each blood type.

Numerous studies show that lectins have a negative effect on the human body.  For instance, in 2004, Vasconcelos and Oliveira’s study, “Antinutritional properties of plant lectins,” found that lectins can act as toxins in the body, especially if they bind to the lining in the gut and digestive tract.

In 2012, another study conducted by B. Vankata Raman et al. titled, “Effect of plant lectins on human blood group antigens with special focus on plant foods and juices” showed that plant lectins interact differently with certain blood types. Blood type A individuals were the least affected by plant lectins and could digest them while blood type O individuals had a harder time doing that.

Therefore, both studies support the blood type diet hypothesis about lectins reacting differently to different blood types.  
Supporters of the diet argue against the claim that there is insufficient scientific evidence to back the diet. They contend that the studies conducted on the blood type diet were often unfairly dismissed because the experimental design criteria did not match some scientific journal requirements.

For instance, some studies examine small sample sizes. Thus, they were not considered reliable because they did not include accurate representations of the population. Supporters of the diet also argue that much of the research conducted to disprove the blood type diet does not follow the scientific method.

Peter D’Adamo, the creator of the blood type diet, claims that the systematic review conducted in 2014 does not prove that the hypothesis behind the blood type diet is incorrect. He says, the study only included 13.7% of foods incorporated in the blood type diet and failed to include food values such as beverages or teas that are a part of the blood type diet, so the study failed to “model the blood type diet.”

Therefore, supporters argue that opponents of the diet should conduct more research to further examine if the blood type diet has any health benefits before making any assumptions about it.

They should make sure that the experiments follow proper experimental design approaches and compare the results between people following the blood type diet and those following a normal diet.

Skeptical views on the benefit of Blood Type Diet for Weight Loss

Opponents of the diet argue that the blood type diet does not affect a person’s overall health compared to other diets. This is because lectins in food react with all blood types in the same manner. Lectins are also present in most foods, especially in legumes such as beans, so it would be difficult to avoid them. Plus, once legumes are cooked, their harmful lectins are destroyed.

 A 1980 study, “Lectins in the United States diet: a survey of lectins in commonly consumed foods and a review of the literature,” conducted by Nachbar and Oppenheim shows that lectins have agglutination properties, and lectins in legumes can be harmful to the human body.

However, it does not show that different blood types have different reactions to lectins. Therefore, experts believe that the main theory behind the blood type diet is false.

Experts also claim that the blood type diet is not supported by scientific evidence. In 2013, a study by Cusack et al. titled, “Blood type diets lack supporting evidence: a systematic review,” analyzed studies presenting data about blood type diets. 
They found that these studies were poorly designed because the experiments lacked a control group of people following a standard diet. This works against the diet because it was difficult for researchers to compare the responses of people following the blood type diet to those following the standard calorie restriction diet.

Therefore, researchers could not tell if people’s diseases improved because they followed the blood type diet or because of other factors.

Previous studies have shown some correlation between blood type and the risk of being overweight or obese. However, in the study “ABO blood groups and risk for obesity in Arar, Northern Saudi Arabia,” conducted in 2016 on participants from primary healthcare centers found that there was no association between blood type and obesity.

Another study conducted in 2018 titled, “ABO Genotype Does Not Modify the Association between the ‘Blood-Type’ Diet and Biomarkers of Cardiometabolic Disease in Overweight Adults,” found that, although people did lose weight during the experiments, it was due to other factors and not their compliance with the blood type diet.

They found no correlation between weight loss and the blood type diet. Therefore, a diet that prescribes specific foods for particular blood types is pointless.

Nevertheless, most doctors like Dr. Nancy Rahnama, a Board Certified Internist and Clinical Nutrition Specialist, agree that the diet can be beneficial if people choose to try it because it promotes healthier eating habits such as eating fresh or organic fruits and vegetables. It also recommends avoiding high sugar foods, simple carbohydrates, and processed meats.

Furthermore, the diet’s opponents agree that some people might see great weight loss results on the blood type diet. This is because the diet restricts certain food groups that lead to weight gain like grains. People also consume fewer calories on the blood type diet because it eliminates specific food groups, which leads to weight loss.

Kris Sollid, senior director of nutrition communications at the International Food Information Council Foundation, explains, “Any diet can lead to weight loss, but that’s related to the number of calories you eat, your age, and how active you are.” He advises people to remember that even if they lose weight while on a diet, that does not mean that the diet is beneficial. 
Therefore, opponents argue that specific foods do not affect particular blood types in different ways. It is the amount and quality of the food people eat, rather than the types of food they eat that can lead to weight loss.