Dietitians warn against risky, ineffective 'blood-type-based' dieting

The claim was posted here on Weibo with an image on June 7, 2023, where it was shared over 2,000 times.

"My blood type is B and I realised I could not lose weight by just eating eggs, chicken and corn regardless of how little calories I take in and the effect is better if I eat anything else," simplified Chinese text in the image reads. "Don't disbelieve it, I did not believe it at first, I only found out after trying it out!"

Another image shared in the post shows an article titled "blood type weight-loss and diet" and makes claims about the different ways blood type affects the "strength" of a person's digestive system.

"No wonder I can't lose weight," the post's caption in simplified Chinese reads. It includes the hashtags "turns out weight-loss is really associated with blood type" and "which weight-loss method is most effective?"

Blood type is hereditary and there are four main blood groups -- A, B, AB and O -- determined by the presence or absence of certain antigens, according to the American Red Cross (archived link).

Image

Screenshot of the false post, taken on June 29, 2023.

Like in other countries, social media in China can play a role in propagating what the ideal body should look like. Viral posts online -- often around challenges demonstrating how thin a person is -- can encourage body-shaming and bullying and tap into the dominant beauty ideal of pale skin and thin bodies (archived link).

False claims about the "blood type diet" were also shared on Weibo and Facebook, while posts with the hashtag "turns out weight-loss is really associated with blood type" garnered more than 97 million views on Weibo.

Similar claims have circulated on Chinese-language online forums since at least 2004, as well as on Facebook since 2011 and in English-language posts since 2012.

But dietitians told AFP the claims were unsubstantiated and warned against following diets that could potentially be harmful.

Lacking scientific evidence

"There is a lack of scientific evidence supporting the efficacy of the blood type diet, with several studies refuting its claims and others suggesting potential benefits unrelated to blood type," said Edward Li -- a dietitian registered with the Hong Kong Dietitians Association (HKDA) -- on July 5 (archived link).

Li said a study published in December 2020 in the Journal of the Academy of Nutrition and Dietetics found "no significant differences in any outcome" between individuals of blood type A or O -- who have a higher and lower risk of cardiovascular disease respectively -- to other participants who took on a low-fat vegan diet (archived link).

Another study published in 2014 in the peer-reviewed PLOS One journal had a similar finding (archived link).

The 2014 study went on to say blood type diets are popular because of their emphasis on consuming whole foods, avoiding processed foods and engaging in physical activity. Li told AFP those recommendations "align with the principles of various diets and are commonly advised by healthcare professionals to enhance overall health".

"It is crucial to acknowledge that there is no universal 'one-size-fits-all' diet," he said.

Teresa Fung, a professor of dietetics at Simmons University in the United States, told AFP on July 7 that although people's ability to digest food varies in some ways, there is no scientific proof that such variation is due to their blood types.

"Each (of those diets) requires avoidance of some foods that have no scientific basis," she said.

Fad diet

Rekha Menon, another dietitian registered with the HKDA, also dismissed the effectiveness of "blood type diets".

She told AFP on June 26 it was a type of deceptive "fad diet" that gained momentum after naturopath Peter J. D'Adamo published his 1996 book "Eat Right For Your Type" about the purported weight-loss method (archived link).

"Following such a diet, long or short-term, without counsel and supervision of a medical professional can be extremely harmful," she warned.

She also said such a method of dieting was risky as it encouraged people to omit major food groups without a formally diagnosed allergy or medical condition, adding it may "lead to malnutrition, muscle loss, severe nutrient deficiencies and associated risks".

She went on to say while there may be some initial weight loss, the diet was unrealistic to maintain.

"If you're looking to lose weight and keep the weight off, the best approach is to seek support from an accredited dietitian, who can provide evidence-based recommendations tailored to you," she said.