In his clinical assessment, Private Kamanzi, a dietician and nutritionist at Amazon Nutrition Cabinet in Kigali that deals with diet, physical wellness, and lifestyle, says he comes across many clients who are misinformed about weight loss and blood type diet.
The nutritionist explains that most of them seek a diet that can help them lose weight depending on their blood group.
This, Kamanzi says, has not yet been scientifically proven to be true, and so far, there are no authorised studies that have found a relationship between blood type diet and weight loss.
“This is a controversial issue where people are being misinformed from what they read on the internet, or told by other people. Although there is still a lot of research going on about this, nothing so far supports the logic behind weight loss and blood type diet,” he says.
In his field, Kamanzi says, the recommendation is reduced consumption of simple sugars, moderate consumption of protein, increased consumption of fruits and vegetables and exercise, and the end goal is always to lose some weight.
When prescribing a diet, he says, there are guidelines they follow and these guidelines have been published by authorised institutions, and none have found a connection between blood type and weight loss.
“People should stick to balancing their diets, eat depending on what their body requires, age, health status, and other factors, and do away with blood group and diet,” he says.
Understanding blood type and body weight
Dr Swaibu Gatare, Division Manager of the National Centre for Blood Transfusion (NCBT) at Rwanda Biomedical Center, says understanding blood group is important whereby blood type is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells.
These antigens, he says, may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system.
When it comes to what blood type (or blood group) one has, Swaibu says it’s all about the antigens—the various sugars and proteins on the surface of our cells, including our blood cells.
Which antigens you have or don’t have on your red blood cells determines your blood type. Antigens are genetically determined—inherited from a combination of your parents’ genes.
There are many different blood type systems, but most people will be familiar with the two main blood groupings—the ABO and Rh (or Rhesus) systems. These systems lead to the eight commonly known blood groupings.
There are 4 main blood groups (types of blood) – A, B, AB, and O.
Dr Everest Ntaganda, the head of non-communicable disease division at Rwanda Biomedical Center (RBC), says it is simply Body Mass Index (BMI) which is calculated using a person’s height and weight.
He says that if your BMI is less than 18.5, it falls within the underweight range. If your BMI is 18.5 to 24.9, it falls within the normal or healthy weight range. While if your BMI is 25.0 to 29.9, it falls within the overweight range.
When the BMI is 30.0 or higher, this falls within the obese range.
Ntaganda says other factors, such as the ratio of waist-to-hip size, waist-to-height, and the amount and distribution of fat on the body, also play a role in determining how healthy a person’s weight is.
What science says
Kamanzi explains that looking at blood cells and the receptors that are attached to the blood cell, it doesn’t indicate any relationship on what type of food one should eat to lose or maintain just because they have a certain blood group.
The 2013 study by Harvard University analysed the world’s medical literature and found no studies demonstrating benefit from a blood type diet. In 2014, it found that while people following any of the blood type diets had some improvement in certain cardio metabolic risk factors (such as cholesterol or blood pressure), those improvements were unrelated to blood type.
Kamanzi goes on to note that from dietary science, there is what causes the body weight imbalance, explaining that when one consumes fewer calories than the body requires, they will lose weight, and on the other hand when they take in more than what is needed, they automatically increase their body weight regardless of the blood type they have.
“In short, there is no blood group that tolerates eating a certain type of food, eating less or more. The logic still remains on what you are taking in versus what you are using up in terms of energy,” he says.
Meanwhile, Kamanzi notes that there is a daily recommended energy requirement that is needed for one to maintain their body weight, and it ranges from 1800 to 2100 kilocalories in a day.
In normal circumstances, when one takes food that provides more than 2100 kilocalories per day on a routinely basis, they end up gaining weight.