A not-so-beginner’s guide to insulin and insulin resistance

insulinInsulin is a hormone involved in the regulation of many vital processes in the body. Problems with this important hormone can lead to a number of common modern health issues.

When cells no longer respond to insulin the way they’re designed to, it’s called insulin resistance; a study conducted in 2002 indicated nearly a third of Americans may be suffering from this condition. (1)

Among certain groups, the problem is even more widespread.

Estimates for the number of obese women with insulin resistance run at 70%, and obese children and young adults may clock in as high as 33%. (2, 3)

In many cases, lifestyle modifications can result in dramatic improvements in this condition. Read on to find out about causes and how to overcome insulin resistance.

Insulin 101

Secreted by the pancreas, insulin controls nutrients in the blood; its main job is to regulate blood sugar levels, but it also plays a role in the metabolism of protein and fat.

The carbohydrates in meals increases the amount of sugar in our bloodstreams, and pancreatic cells sense the change and release insulin, which circulates in the blood, signaling cells to pick up sugar.

Cells follow orders, taking up sugar for energy use or storage, and blood sugar levels drop; but if this process isn’t working, blood sugar levels stay high, leading to imbalances that can cause harm or even death when levels are extremely elevated.

Insulin resistance occurs when cells no longer respond to the message delivered by insulin. The pancreas secretes more insulin to try to fix the situation, and excess circulating insulin can build up to create a condition called hyperinsulinemia.

This can go on for a long time, with blood sugar and insulin levels continuing to rise; the issue can eventually lead to a diagnosis of type 2 diabetes, a serious disease that affects nearly one in ten people worldwide. (4)

Note the distinction between insulin resistance and insulin sensitivity:

  • Insulin resistance means your insulin sensitivity is low
  • Insulin sensitivity means you are sensitive to the message insulin is delivering to cells

So insulin sensitivity indicates normal function, where cells respond to the message to uptake sugar from the blood, while insulin resistance is the opposite circumstance that results in high blood sugar levels.

Causes of Insulin Resistance

Researchers believe one of the main triggers for insulin resistance is elevated levels of free fatty acids in the blood. (5)

The build-up of fatty acid metabolites and fats inside muscle cells, for example, may block signals sent by insulin; the term for this build-up is intramyocellular fat. (6)

This type of fat accumulation is due to eating more calories than necessary and packing around excess weight. Obesity, weight gain and overeating are all associated with developing insulin resistance. (7)

Belly fat that can build up around the organs is thought to release fatty acids into blood, along with inflammatory hormones leading to insulin resistance. (8)

People who aren’t overweight can also be insulin resistant, but it’s not as common. (9)

Other potential causes for insulin resistance include:

  • High fructose intake from a diet high in sugar (added sugar, rather than whole fruit) (10)
  • Inflammation and high levels of oxidative stress (11)
  • Sedentary lifestyle (12)
  • Imbalances in gut bacteria (13)

Social factors, heredity and race may also play a role in establishing risk factors for insulin resistance; studies show Asians, blacks and Hispanics are more likely to develop this condition. (14)

Are You Insulin Resistant?

If you’re overweight and have a lot of belly fat, you may be insulin resistant. Besides having high fasting blood sugar levels, there are several other ways to determine if you’ve developed insulin resistance.

HOMA-IR is a fairly accurate blood test used to estimate resistance from insulin and blood sugar levels. Oral glucose tolerance tests are another method; after an oral dose of glucose is given, blood sugar levels are tested over the following few hours.

Acanthosis nigrans is a skin condition where dark spots appear on the skin, sometimes indicating insulin resistance.

Low levels of HDL cholesterol (the good kind), as well as high blood triglyceride measurements, are two other possible signs of the condition.

Insulin resistance is present in two extremely common health conditions: type 2 diabetes and metabolic syndrome.

Metabolic syndrome, also called insulin resistance syndrome, is a combination of risk factors associated with heart disease, diabetes, and other health problems, including: (15, 16)

  • Elevated blood pressure (hypertension)
  • Central obesity (high amounts of belly fat)
  • Elevated blood sugar
  • Low HDL cholesterol
  • High measurements of blood triglycerides

Insulin resistance is associated with type 2 diabetes as well; cells no longer respond to insulin, and eventually the pancreas cannot keep up with the demand for more. An insulin-deficiency develops. (17, 18)

Stopping this process may result in preventing type 2 diabetes and metabolic syndrome; people with these conditions are 93% more likely to get heart disease. (19)

Other chronic diseases associated with insulin resistance include:

  • Fatty liver disease (non-alcoholic) (20)
  • Polycystic ovarian syndrome (PCOS) (21)
  • Alzheimer’s disease (22)
  • Cancer (23)

Improve Insulin Sensitivity and Reduce Resistance

Insulin resistance does not have to lead to serious health issues. In many cases, simple lifestyle choices can improve or reverse the condition.

Here are ten changes you can make to positively influence insulin sensitivity:

  1. Increase the amount of exercise you get (24)
  2. Reduce belly fat
  3. Quit smoking tobacco (25)
  4. Eat less sugar and stop drinking sweetened beverages, especially sugary sodas
  5. Base your diet on whole foods, including fish and nuts
  6. Get adequate omega-3 fatty acids (26)
  7. Add supplements like berberine and magnesium (27, 28)
  8. Improve the quality of your sleep (29)
  9. Manage stress (30)
  10. Practice intermittent fasting (31)

Eating a low-carb diet has also been shown to improve health markers linked with type 2 diabetes and metabolic syndrome, partly through positive effects on insulin resistance. (32, 33)

While this list isn’t intended as medical advice, note that the suggested actions are all associated with good health habits.

Summary: Evidence shows insulin resistance can play a role in raising risk factors for many modern chronic diseases; making lifestyle choices that help prevent or correct this vital issue may be one of the most positive actions you can take to enjoy good health.

References:

  1. http://www.ncbi.nlm.nih.gov/pubmed/17967708
  2. http://www.ncbi.nlm.nih.gov/pubmed/22766891
  3. http://www.ncbi.nlm.nih.gov/pubmed/15613503
  4. http://www.who.int/mediacentre/factsheets/fs312/en/
  5. http://www.ncbi.nlm.nih.gov/pubmed/15919784
  6. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1971250/
  7. http://www.ncbi.nlm.nih.gov/pubmed/20547978
  8. http://onlinelibrary.wiley.com/doi/10.1038/oby.2006.277/abstract
  9. http://www.cdc.gov/nchs/data/nhsr/nhsr013.pdf
  10. http://nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-2-5
  11. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516838/
  12. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2551669/
  13. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3705322/
  14. http://www.ncbi.nlm.nih.gov/pubmed/8633616
  15. http://journals.lww.com/jcnjournal/Abstract/2004/09000/Insulin_Resistance_Syndrome.9.aspx
  16. https://www.nlm.nih.gov/medlineplus/metabolicsyndrome.html
  17. http://www.ncbi.nlm.nih.gov/pubmed/15068125
  18. http://press.endocrine.org/doi/full/10.1210/jcem.84.4.5612
  19. http://www.ncbi.nlm.nih.gov/pubmed/15983333
  20. http://www.ncbi.nlm.nih.gov/pubmed/20370677
  21. http://www.ncbi.nlm.nih.gov/pubmed/17185787
  22. http://www.ncbi.nlm.nih.gov/pubmed/12467491
  23. http://www.hindawi.com/journals/jdr/2012/789174/
  24. http://www.ncbi.nlm.nih.gov/pubmed/10683091
  25. http://www.ncbi.nlm.nih.gov/pubmed/8463765
  26. http://www.ncbi.nlm.nih.gov/pubmed/24564669
  27. http://www.ncbi.nlm.nih.gov/pubmed/25861268
  28. http://www.ncbi.nlm.nih.gov/pubmed/14693979
  29. http://www.ncbi.nlm.nih.gov/pubmed/20371664
  30. http://www.ncbi.nlm.nih.gov/pubmed/23444388
  31. http://www.sciencedirect.com/science/article/pii/S193152441400200X
  32. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2633336/
  33. http://www.ncbi.nlm.nih.gov/pubmed/15616799
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