Why are Japanese Sumo Wrestlers Called 'Healthy Obese'? - The Surprising Answer!

Cardiovascular disease and stroke are the leading causes of disability and death in adults. Obesity is one of the major contributors to this condition. Overweight and obesity are considered diseases of the 21st century, with the incidence of the disease increasing and becoming younger.

According to WHO, overweight is a condition of weight exceeding the threshold appropriate for current height. Obesity is a condition of excessive and abnormal fat accumulation in a part of the body or the whole body, causing many health risks such as cardiovascular disease, dyslipidemia, diabetes or musculoskeletal diseases, etc. BMI has long been used to assess overweight and obesity. BMI from 25 - 29.9 is considered overweight, and > 30 is considered obese.

However, an interesting piece of information posted by Japanese researchers on ResearchGate, Japanese Sumo wrestlers appear to be overweight (usually weighing 130-180kg), with a large waistline, BMI 35.5-36.5, much higher than normal people, and do not suffer from obesity-related diseases such as high blood pressure, diabetes, stroke , etc. and they look really strong, agile, and flexible on the ring.

Sumo is a long-standing traditional sport in Japan and is considered a symbol of strength for the people here. Japanese researchers revealed that the CT scans of Sumo wrestlers have very little visceral fat in their bodies, but mainly subcutaneous fat. Blood tests also showed that their blood sugar, blood cholesterol and blood triglyceride levels were low, helping them avoid complications of obesity and are considered healthy obese people.

Why is that interesting? The answer lies in the distribution of body fat and the diet and training of Sumo wrestlers. 

Sumo is a long-standing traditional sport in Japan and is considered a symbol of the strength of the people here. (Illustration photo).

The reason why Sumo wrestlers are called "healthy obese"

Normally, body fat is distributed into two forms.

1. Subcutaneous fat 

Subcutaneous fat is the most common type of fat, located just under the skin, concentrated in the buttocks, hips and thighs. This fat can be seen with the naked eye or measured with a caliper. It is usually relatively safe and harmless.

2. Visceral fat

Visceral fat is a layer of fat located deep in the body's cavities, surrounding organs such as the heart, liver, intestines, pancreas, etc. and can only be identified through computed tomography (CT) or magnetic resonance imaging (MRI). However, these tests are often expensive, time-consuming and recommend using waist circumference for prediction. Many studies have shown that this layer of visceral fat is the cause of dangerous health problems.

Visceral fat increases insulin resistance – a hormone secreted by the pancreas that lowers blood sugar. Therefore, obese people are at risk of diabetes, increased inflammatory response of the body, increased atherosclerosis, causing damage to the cardiovascular system and other organs in the body.

Even if you have a normal BMI and normal weight, this amount of fat can still accumulate in the body and cause complications. When the subcutaneous fat layer is too high, it tends to convert into visceral fat.

In addition, we need to pay attention to the waist circumference , which is the circumference of the waist – the narrowest part of the abdomen, the midpoint between the lower edge of the last rib and the top of the iliac crest, above the navel. Waist circumference in men > 90 cm and in women > 80 cm in Asians has been shown to increase the risk of cardiovascular disease and diabetes.

Waist circumference is the circumference around the widest part of the hips. WHR is the ratio of waist circumference to hip circumference, which is how doctors can see if excess weight is a health risk. According to the WHO, a WHR of 1.0 increases the risk of cardiovascular disease and other diseases related to being overweight.

BIM is a tool based on the relationship between weight and height to assess whether the body is overweight or not without taking into account the distribution of body fat. Therefore, it is difficult for doctors to predict the risk of disease in patients based on BIM alone. WHO has added waist circumference and waist-to-hip ratio (WHR), which are considered useful tools in predicting the risk of cardiovascular disease. Many people confuse waist measurement with waist measurement.

In men, fat is usually stored more around the waist, while women often store fat around the hips and thighs. 

Sumo wrestlers have a strict training and diet regimen. (Illustration photo)

Returning to Japanese Sumo, the above condition is due to high intensity training , usually starting at 5am, lasting continuously for 5 hours and a strict diet. High intensity training helps the body increase the release of the hormone adiponectin . This hormone is secreted by fat tissue and has the effect of increasing insulin sensitivity, helping to stabilize blood sugar, avoiding the risk of diabetes and promoting the distribution of subcutaneous fat, reducing visceral fat mass. However, when no longer competing, the subcutaneous fat layer will transform into visceral fat and harm the body.

Therefore, to truly reduce visceral fat, in addition to diet, exercise is required. To assess general health status, in addition to BMI, waist circumference and waist/hip ratio also contribute to assessing the risk of cardiovascular disease and other related diseases more accurately.