Why do SO MANY South Asians become diabetic? (Pt 2: The Solution)
Thin on the outside but fat on the inside: the Asian phenotype
This article follows on from my previous post ‘Why do SO many South Asians become Diabetic? (Part 1: The Problem)
In 2004 Dr John Yudkin and Dr Chittaranjan Yajnik published a paper in The Lancet describing the Y-Y paradox.
The Ys represented their surnames.
The paradox was that whilst both men had a BMI of 22.3 (a normal BMI is 18.5–24.9), a detailed scan of their body composition showed that the body fat of the two men was vastly different; Dr Yudkin ran marathons and had a body fat percentage of 9.1%. Dr Yajnik however — whilst seemingly slender — had a body fat percentage of 21.2%, more than double that of his friend!
We now understand that one part of the puzzle is that South Asians are more likely than white Europeans to have a physiology known as ‘Normal weight obesity’ (NWO) and that this makes them more likely to develop diabetes.
Normal weight obesity is where fat is stored around internal organs long before it is apparent that the person is overweight. We know that fat is not simply an inert store — it is hormonally active which is why carrying those extra pounds is a risk for so many health conditions.
What is more, South Asians typically have less lean body mass. Lean body mass is what is left over when we take our weight and minus the body fat component; It includes the total weight of our organs, bones and importantly skeletal muscle. Skeletal muscle soaks up 70–90% of the glucose that is released into our blood after eating, so it is very important in blood sugar control.
Taken together, the hidden fat and low amount of muscle is not a great combination for keeping blood sugars low.
The Exhausted Pancreas
Studies looking at levels of insulin and other hormones at different life stages — from birth to the first decade of life and early adulthood — have found that even in lean South Asians without diabetes, there is a chronic level of insulin resistance compared to Caucasians.
What is more, it seems that South Asians exist in a kind of insulin resistant state up to the age of about 60 years, and then their pancreas just starts to give up. They then begin the slump into clinically apparent diabetes. In fact, because their pancreas has spent the past 60 years working overtime it has less reserve and the decline is more rapid and the consequences worse.
Caucasians on the other hand slowly become more insulin resistant with increase in adiposity (amount of fat) and loss of skeletal muscle mass with age. But because they haven’t spent their entire lives in a state of insulin resistance they are able to compensate so they do not deteriorate so quickly.
Genetic studies are not able to explain this.
However, epigenetic studies do seem to offer an explanation.
It is now thought that when Asian mothers are pregnant they are more likely to be slightly insulin resistant which causes changes to the foetus and makes them more likely to switch on genes that increase fat storage and insulin resistance tendencies.
This is likely due to the ‘thrifty gene’ hypothesis.
Diabetes is often thought of as ‘starvation in the midst of plenty’. Although there is a lot of glucose and insulin in the blood, the (pre)diabetic body just doesn’t notice it because it is insulin resistant. That is why it releases more glucose from the liver and stores fat.
In the foetus of the insulin resistant mother, genes are being switched on to say ‘you will be born into an environment where there is not enough food — make sure you store as much glucose and fat as possible when you are born into this world’.
Some authorities suggest that screening of pregnant women for diabetes risk should be undertaken at a lower threshold for Asians, and lifestyle advice and support should be offered to mitigate this risk. Lifestyle intervention at this stage would improve the metabolic risk to both mother and her unborn baby.
When to start preventing diabetes
As you can see, preventing diabetes in South Asians (and indeed everyone!) really should start from the womb!
But, suppose you’ve missed that boat, what should you do?
A recent study divided 3539 individuals who were at risk of diabetes (2 or more of: positive family history, physical inactivity, waist circumference or high BMI) and divided them into two groups:
Group 1 were given lifestyle advice once per year
Group 2 were given lifestyle advice 3 times per month
Interestingly the people who were recruited varied in age from 5 years to 40 years (average age 22 years). So they were much younger and healthier than most studies looking at lifestyle intervention to avoid diabetes.
Dietary advice included cutting down on refined carbohydrates, simple sugars and saturated fats, whilst increasing intake of fibre-rich foods such as wholegrains, legumes, vegetables and fruits.
Advice on physical activity promoted 30 minutes of exercise per day for those who were inactive, and 1 hour of active play per day for children. All participants were encouraged to cut down on sedentary activities such as playing computer games and watching television.
After 3 years, when they compared the number of people in Group 1 and 2 they found that there was a significantly lower rate of high blood pressure, newly diagnose pre-diabetes and diabetes in Group 2 vs Group 1. When they separated out the under and over 18s, they found that the younger participants in Group 2 fared much better than those in Group 1 — in fact they had 40% lower rates of high blood pressure, and 52% lower rates of newly diagnosed diabetes than those in Group 2.
Going back to my parents’ — their diet was pretty good. So where did it go wrong? Check back soon to read my follow on article ‘What is Wrong With the South Asian Diet?’
*BMI = body mass index. Calculated as height (meters) / height ² (meters). It is commonly used to guide us in recognising when someone’s weight, relative to their height, is too high and putting them at risk for health conditions. See this link for more details about BMI.
