A SIMPLE EXPLANATION: INSULIN RESISTANCE & ITS EFFECTS
- October 28, 2015
You may already know that insulin resistance is the underlying cause of type-II diabetes. What is insulin, though? And how do we develop a “resistance” to it?
While Indians have a genetic predisposition to type-II diabetes (India actually topped the world with 62 million people with diabetes in 2014), diabetes and all the other ‘lifestyle diseases’ that we see today are a consequence of urbanisation.1, 2
Here’s a simple explanation of how people develop insulin resistance.
Insulin and Metabolism
Insulin is a hormone that plays a big role in metabolism, which is all about how our body converts digested food into energy.
Let’s start from the beginning:
Our digestive track breaks down the carbohydrates we eat into glucose as well as other simple sugars. Our bloodstream then delivers glucose across the body, for our cells to use as energy.
That’s where insulin comes in.
It’s a hormone produced by our pancreas, to help blood glucose enter into the cells. You can think of it as the key that opens the cell’s door, allowing blood glucose to enter.
‘Insulin resistance’ simply means that the cells of our body have slowly stopped responding to insulin – it can no longer open the door.
Although cells have other ways of taking up glucose, this definitely causes an imbalance in our blood glucose levels, and even impairs the functions of cells.3
The condition of ‘insulin resistance’ is known as type-II diabetes mellitus. This is different from type-I diabetes mellitus, where the body cannot make insulin in the first place, making it necessary for the patient to inject insulin into their blood.
What Makes Our Cells Resistant to Insulin?
Our blood glucose level increases after a meal, thanks to the hard work done by the digestive tract.
The pancreas responds to this high blood sugar by releasing insulin into the bloodstream – the insulin makes the cells take up the blood glucose, and the level of it in our blood returns to normal.
The modern diet has changed this in a fundamental way.
Now, the blood sugar is consistently high over a long period of time. This makes the cells take way more blood glucose than they need. They want to keep that door closed to it, so they start rejecting the action of insulin. Over time, this leads to a permanent condition of insulin resistance.
Meanwhile, the pancreas keeps dutifully producing insulin, because the blood glucose level is still high.
This leads to two possibilities:
1] There is too much insulin in the blood (causing other complications)
2] The pancreas gets fatigued and makes less insulin
Either way, there is an imbalance in the system.
Keep in mind though, that along with this blood glucose, there are various fats, hormones, pro-inflammatory compounds etc. also entering the cell.
So, in obese individuals, insulin resistance can develop for more reasons than just the excess glucose. The expanded fat tissue releases higher than normal amounts of all of these into the blood, which also leads to the development of insulin resistance by the cells.4
Insulin Resistance and Diseases
1] Free Radical Damage
When glucose is converted to energy, free radicals are produced as part of the process.
So, when there’s too much glucose in the blood, that creates too many free radicals, leading to problems like skin ageing and many diseases, including cancer5.
2] Fat Metabolism
Insulin is also involved in the way fat is used and stored. This basically means that when there is too much insulin, or it can’t be used, there could be an imbalance in the levels of free fats and bad (LDL) cholesterol in the blood.
When these levels are too high, they build up in the liver, muscle, pancreas, heart and vessels, leading to all sorts of problems.6, 7
3] Brain Functions
Insulin resistance even leads to the impairment of brain functions. It plays such a significant role in the changes that occur in the brain during Alzheimer’s disease, that the condition is now being called “type-III diabetes”.8
Causes and Management of Insulin Resistance
Although ageing and our genes do play a role, the two main causes of insulin resistance are obesity and physical inactivity – which can be controlled.
Another bit of good news is that insulin resistance is reversible to a large degree (people with type-II diabetes usually manage it with oral medication).
But there’s so much more you can do.
The spike in blood sugar after eating depends on the type of food we eat. With foods that dramatically spike up blood sugar, the body experiences a ‘blood sugar rollercoaster’, where the drop leads to cravings, and eventually weight gain and insulin resistance.9
How do we identify these foods? There’s a number called the glycemic index (GI) which tells you how much each food raises your blood sugar.10
Example: The GI of fibrous whole wheat bread (about 51), is much lower than that of refined white bread (73). That means refined white bread gives us a lot of glucose quickly – possibly with some added sugar as well – which also means that we get hungry sooner (remember the blood sugar rollercoaster).
There are several books, websites and smartphone applications that are dedicated to helping you get this information about your food.
However, generally speaking, a balanced, healthy diet that’s full of fruits and vegetables can keep you in the clear if you don’t overeat.
When muscles are active, they burn their stored glucose for energy. They then use glucose from the bloodstream to refill their reserves – keeping the blood glucose levels in check.
A single bout of exercise can increase insulin sensitivity for at least 16 hours after it.13, 14
3] Sleep and Hormonal Balance
Sleep disturbances, including insufficient sleep, poor sleep quality, and obstructive sleep apnoea have been associated with insulin resistance.
Women with PCOS (Polycystic Ovary Syndrome) have a high risk of early-onset type-II diabetes, as well as an increased risk for high blood pressure and heart disease. PCOS and poor sleep quality seem to be linked, which may explain the increased risk of insulin resistance.15
It’s a good idea to notice your body’s individual trends over time. Do you feel fatigued or thirsty all the time? It may well be nothing, but probing every now and then won’t hurt.
We now know there’s a condition known as prediabetes, where blood glucose levels are above normal but below the threshold of diabetes. An estimated 77.2 million people in India (as of 2012) suffer from it.16 Studies have shown that lifestyle interventions in prediabetic adults can reduce diabetes risk by 40-70%.17
We are constantly finding new insights about our food and new ways to stay healthy. Looking out for them may do us all a lot of good.
In view of all this, the old adage of eating healthy, sleeping well and exercising regularly takes on a whole new meaning. Small changes in our lifestyle can help our body in ways that we only realise once we begin to take charge of our health!
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5. Lobo V, et al. Pharmacognosy Reviews 2010, 4(8): 118-126.
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8. de la Monte SM, Wands JR. J Diabetes Sci Technol 2008, 2(6): 1101-1113.
9. Burn G. Healthy Mind and Body All-in-One For Dummies. Wiley, 2009.
10. Wilkins LW. Diabetes Mellitus: A Guide to Patient Care. Lippincott Williams & Wilkins, 2007.
11. Neelakantan N, et al. Nutrition Journal 2014, 13: 7-7.
12. Qin B, et al. Journal of Diabetes Science and Technology 2010, 4(3): 685-693.
13. Borghouts LB, Keizer HA. International journal of sports medicine 2000, 21(1): 1-12.
14. Ivy J. Sports Medicine 1997, 24(5): 321-336.
15. Van Cauter E. Diabet Med 2011, 28(12): 1455-1462.
16. Ramakrishna BS, et al. ECAB Probiotics in Prevention of Lifestyle Disorders. Elsevier Health Sciences APAC, 2014.
17. Bansal N. World Journal of Diabetes 2015, 6(2): 296-303.
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