From devising parameters to gauge your risk for metabolic disorders to identifying the virus that might be responsible for obesity, Dr Nikhil Dhurandhar, associate professor, Infections and Obesity Laboratory, Pennington Biomedical Research Centre, Louisiana State University System, LA, has been in the forefront of the battle of the bulge. Here, Dr Dhurandhar, son of well-known weight-management guru Dr Vinod Dhurandhar, talks about the damage that obesity can inflict on the body and the need to look at the bigger picture, beyond the conventional BMI parameter to gauge metabolic disorders among Indians.

Q Recent scientific studies in the West indicate BMI does not play an important role in determining a person`s risk for cardiovascular disease and type 2 diabetes, contrary to earlier wisdom. How did this change come about?

It is true that there has been a controversy on whether BMI is a better indicator of your risk for metabolic disorders or not. It is possible to have better indicators. When you carry out more tests, you get a better picture of a person`s risk for metabolic disorders. This stands true at an individual level. However, when you are trying to gauge the risk for a certain population, you need an approach that does not involve too many tests and yet gives a good enough picture of the risk factor. In this context, BMI and waist circumference (WC) are effective tools to determine the risk factors for a population as they can be measured fast and easily. So when health experts and researchers realised this distinction, they decided to change the existing guidelines (see box).

Q Why is BMI such an important tool for calculating risks for cardiovascular and metabolic disorders?

When researchers in the West were trying to map health risks they discovered that people who had BMI greater than 25 were in the high-risk category, and the risk skyrocketed in people with BMI of more than 30. So over the years, based on studies, we got these cut-off limits for BMI 18-25 normal (this parameter has changed for Indians see box), more than 30 obese. These numbers help the experts determine who needs intervention and who can do without it. However, these numbers are not foolproof. If you have a BMI of 24.5, technically you are in the `safe` zone (this is not true if you are Indian) but you may still need medical intervention to cut your risk. These numbers are just indicators; they don`t promise that you will or will not have metabolic diseases. You need to look at the larger picture.

Q A recent study published in the Journal of Association of Physicians of India reiterates the importance of BMI and WC, and how both should be used together for metabolic and cardiac risk stratification. Why is there a difference of opinion among experts in India and the West on this?

I have been following the work of Dr Anoop Misra, the leader of this study. In the course of his study he found that for any given value of BMI, Indians had a higher risk compared to Caucasians. To be able to explain why, you need to have better understanding of BMI. BMI is a reflection of your body fat. So in theory two people with the same BMI should have the same body fat. But that`s not so, as Dr Misra realised. An Indian with BMI 23 had more body fat and less muscle mass whereas a Caucasian with the same BMI had less fat and more muscle mass. The next step was to compare an Indian and a Caucasian with the same BMI and body fat percentage. Still the risk for the Indian came out to be higher. A possible explanation for this is that Indians have more visceral fat (around internal organs). As studies show, this fat is what increases your risk for metabolic diseases. Therefore, the scientific community has come to the conclusion that Indians, compared to Caucasians, have a higher risk of metabolic disorders at any given BMI. This led Dr Misra`s team to develop new cut-off values for BMI and WC for Indians (see box) which are lower than those for Caucasians.

Q Is the waist-to-hip ratio also a good indicator for metabolic disorders?

This was developed quite a while ago but has now fallen out of favour. The wisdom was that waist-to-hip ratio should not be greater than 1. For instance, if your waist is 30” and hips also 30”, your ratio is 1. But if your waist is 40” and hips 30” then the ratio is 1.3 indicating a higher risk. However, it was seen if your waist is 60” and hips 65” your ratio is .92, you still run a high risk. So the ratio does not give a correct picture in many people. Hence experts focussed mainly on WC and BMI. Now the wisdom is that WC and BMI are pretty good indicators of gauging the risk of metabolic disorders among Indians.

Q You have been researching the AD36 virus for 10 years to ascertain if it causes people to get fat. What is the current understanding?

I have been studying the connection between the virus and obesity since the `80s. A chance conversation with a family friend who happened to be a veterinary pathologist studying avian adenovirus that was killing poultry revealed that chickens infected with this virus had abdominal fat. It got me thinking: how come the chickens that were dying were getting fat? I started experimenting by infecting chicken with this virus. In 3 weeks, the chickens became fatter and interestingly reported low levels of cholesterol and triglycerides. We repeated with larger numbers and got the same results. Later, in the US, I studied humans who had antibodies for AD36 a different adenovirus that infects humans and causes obesity in many animal models, including monkeys. They, too, showed higher body fat, high BMI but low cholesterol and triglycerides. After many more experiments, my team and I are now trying to understand the mechanism of this virus. It seems that the virus increases the number of fat cells in the body. It infects normal adult stem cells and turns them into fat cells. But we need to find out more about the exact mechanism.

Q Is it okay to be overweight if one follows a healthy lifestyle no smoking/drinking, exercise every day, eat healthy food and stay positive?

This is a very relevant question but we really don`t have a complete answer right now. There`s something called metabolically normal obesity. People with this condition are overweight but have the metabolic profile of a lean person. On the other hand you have people who are not overweight but exhibit the metabolic profile of an overweight person. Now, if you ask if a person with metabolically normal obesity has a lower risk of metabolic disorders, the answer is we don`t know yet. If you are obese, but metabolically normal, do you need to lose weight? I think you should. This is because obesity results in mechanical problems like joint damage and hernia. You don`t need that, right? Plus, over time, when you are 55 or 60, you may develop diabetes, even if you don`t have it now.

5 most important indicators for risk of metabolic disorders in Indians