The Thin Fat Indian

‘But he doesn’t look obese or overweight, how can he have heart disease?’
As Indians we all know someone who does not apparently look overweight or obese but has a cardiometabolic disease like high blood pressure, type 2 diabetes or heart disease. This is because of a typical phenotype called thin fat individual found in tropical countries. Thin fat individual is an individual who has normal body weight (as measured by body mass index) or looks thin but has a disproportionately high body fat percentage. The thin-fat
phenotype is known by several other names in the scientific literature including normal weight obesity, metabolic obesity, metabolically unhealthy non-obese, TOFI(thin outside fat inside) etc.

Why is it so important to identify a normal weight obese person?

This phenotype is associated with a high cardiometabolic risk similar to individuals with overt obesity. Moreover, the mortality associated with this phenotype is also significantly
higher than nonobese subjects and hence, it is important that people are aware of its existence.

What causes a person to be thin outside and fat inside?

The key factors implicated in the development of thin fat phenotype are genetic
predisposition, low birth weight, maternal malnutrition and fat overflow hypothesis. According to this hypothesis, south Asians have a lower capacity to store fat in subcutaneous region. When exposed to a high calorie intake ,the extra fat spills to ectopic sites like omentum,kidney,heart,intestine and liver.T his leads to a higher amount of visceral adipose tissue.But before blaming genetics and other factors,it is important to note that the
same lifestyle choices that lead to obesity can also lead to normal weight obesity.This includes poor dietary choices,lack of exercise,poor sleep and high stress.

The YY Paradox

This unique south Asian phenotype was classically described in a seminal paper published in the Lancet in the year 2004 called the YY Paradox . This pictorial abstract compared the
body mass index and body composition of a Caucasian and an Indian physician. It showed how despite both having a similar normal body mass index (22.3 kg/m2), the body fat content was much higher in the Indian doctor. (21.2% vs 9.1%).

Keeping this in view,there has been a consensus to use different cut offs to define obesity in South Asian population.

The different defining parameters for South Asians:

For South Asians a BMI of 23 to 24.9 kg/sq.m is overweight and a BMI OF 25 to 29.9 kg/sq m is obese while for western population a BMI of 25 to 29.9 kg /sq m is over weight and more than equal to 30 is obese.

The most widely used cutoff for body fat percentage in the Asian population is ≥ 20 kg/m2 for men and ≥ 33%in women compared to ≥ 25% for men and≥ 35% in women for western population. The cut off for waist circumference in men is ≥ 90cm in South Asian population while the same is ≥ 102cm for Western population. For women ≥ 80cm is the cut off for South Asians and ≥ 88cm for western population. Waist circumference or waist to hip ratio is a better marker compared to BMI to diagnose these individuals as BMI does not take into account the difference between fat and muscle and where the person is holding fat in the body.

The implications of excess visceral fat

Extra weight around your waist despite being normal weight is dangerous because fat around middle or visceral fat is where the damage starts in terms of insulin resistance and inflammatory proteins. It is like visceral fat almost behaves like an independent inflammatory and disease producing entity.
Another problem with this phenotype is a younger age of development of the cardiometabolic disorders and rapidly increasing prevalence. This translates to significant financial constraints and a suboptimal quality of life.

How do we diagnose?

So, all adults who suspect that they have a normal weight obesity should get body composition screening in addition to routine health screenings. Waist circumference, waist to hip ratio is ,more reliable than BMI. Hydrostatic (or underwater) weighing POD,DEXA Scan, Bio impedance analysis are some of the tests that can give a fairly accurate idea about body composition but are expensive, complicated and hence, not very practical. Some body composition analysers used in a doctor’s clinic are fairly accurate.

Management:

The fact that these people do not look overweight makes them take diet and lifestyle choices for granted. They might end up being more sedentary with poor lifestyle choices for the same reason! .Optimal nutrition that ensures complex carbohydrate intake, fibre and protein intake rather than producing a calorie deficit is important. Adding more plant based whole foods ensures a nutrient rich diet that helps to decrease the inflammation. It is important to eliminate/limit processed food, refined fats and carbohydrates. Strength training is very important for these people because they typically have low muscle mass. Focus on sleep, managing stress and emotional wellbeing is also very important because all these play a very important role in getting the inflammation down and preventing diseases.

Final thoughts

Weighing scale and BMI might not indicate optimal health. Waist circumference, waist to hip ratio and biochemical parameters help in diagnosing the excess visceral fat which is responsible for making a person metabolically unhealthy.
Last but not the least, as with everyone else, thin obese people also need to get their lifestyles right by eating healthy, getting their steps, lifting heavy, sleeping well and prioritizing mental well being