Insulin is essential for our cells to use glucose from the blood. When the body doesn’t respond to insulin, it can lead to insulin resistance. This blog post discusses insulin resistance, its causes, how doctors diagnose it, and ways to prevent and reverse it.

Insulin is a hormone your pancreas makes that moves glucose (sugar) from your blood into your muscle, liver and fat cells for energy.¹ Your body produces glucose from food, but your liver can make it when you do not eat for long periods. When your blood glucose rises after meals, your pancreas releases insulin to lower it, stopping your liver from producing more glucose and keeping it in the normal range.¹

What is insulin resistance?

Insulin resistance is when your muscles, liver and fat cells fail to respond to insulin as they should and cannot take up glucose from the bloodstream.^1,2 This prompts your pancreas to make more insulin to encourage your cells to take up glucose.^1,2 As long as your pancreas produces enough insulin to move glucose into your cells, your blood glucose levels remain normal.

Who is more likely to develop insulin resistance?

People with genetic or lifestyle risk factors are more likely to develop insulin resistance. Genetic conditions that increase risk include:²

• Myotonic dystrophy
• Ataxia-telangiectasia
• Alstom syndrome
• Robson-Mendenhall syndrome
• Werner syndrome
• Lipodystrophy
• Polycystic ovary syndrome (PCOS)
• Type-A insulin resistance (caused by an abnormal insulin receptor gene)
• Type-B insulin resistance (caused by the body attacking itself)

Lifestyle & genetic factors that increase risk include:^{1, 2}

• Overweight and obesity
• Poor sleep
• Stress
• Age (over 40)
• Physical inactivity
• Unhealthy diets/nutritional imbalances
• Medications
• High-salt diets
• High blood pressure
• Abnormal blood fats profile (high triglycerides, high cholesterol, low high-density lipoprotein [HDL or good] cholesterol)
• Heart disease, PCOS, non-alcohol fatty liver disease (NAFLD) or acanthosis nigricans
• Family history of type 2 diabetes, high blood pressure or heart disease

What causes insulin resistance?

Scientists are still uncertain about the cause of insulin resistance, but evidence suggests that unhealthy diets, lack of exercise, and carrying excess fat around the abdomen contribute to its development.

A Caucasian woman with a waist circumference of 80cm (31 inches) or more has a high risk of insulin resistance. Similarly, a Caucasian man with a waist circumference of 96cm (38 inches) or more has a high risk. Women with waist circumference greater than 88cm (35 inches) and men with waist circumferences greater than 102cm (40 inches) have an even higher risk.³

Waist Circumference4	Threshold value
Higher risk cut-off	Men	Women
Canada, United States	≥ 102cm (≥ 40 inches)	≥ 88cm (≥35 inches)
Middle Eastern, sub-Saharan African, Mediterranean	≥ 94cm (≥ 37 inches)	≥ 80cm (≥31 inches)
Asian, Japanese, South and Central American	≥ 90cm (≥ 35.4 inches)	≥ 80cm (≥31 inches)
Chinese	≥ 80cm (≥31 inches)	≥ 80cm (≥31 inches)

What are the symptoms of insulin resistance?

Insulin resistance has no symptoms, but being overweight or obese with high cholesterol and high blood pressure can indicate its presence.

How do doctors test and diagnose insulin resistance?

Doctors do not test for insulin resistance because the only reliable test available is complicated and only used for research.² However, scientists have developed other methods to estimate insulin resistance, such as the homeostatic model assessment for insulin resistance (HOMA-IR). This tool calculates insulin resistance based on fasting glucose and fasting insulin levels.²

The triglyceride to HDL ratio is another metric used to calculate insulin resistance in Caucasians. A ratio of at least 3.5 in men and 2.5 in women indicates insulin resistance.² These ratios do not apply to people of Black descent. However, a triglyceride/HDL ratio of 2.5 can identify insulin resistance in Black men only.⁵ No reliable ratio has been identified for Black women.

How can I prevent or reverse insulin resistance?

Eating a healthy diet, increasing activity, and weight loss is the best way to prevent insulin resistance.⁶ A healthy diet contains fruits, vegetables, nuts, seeds, legumes, starchy carbohydrates and wholegrains. Eating adequate portions and limiting the intake of foods high in sugar, salt and saturated fat, such as chocolate, sweets, pastries, crisps, ice cream and desserts, is also important.⁷

Aim for at least 150 minutes of weekly activity, including aerobic exercise such as brisk walking, running, jogging, HIIT training or cycling and strength-training exercises, such as weight-lifting and callisthenics.⁶ In clinical studies, exercise improves insulin sensitivity and supports weight loss.^{2, 6}

If you have overweight or obesity, aim to lose at least 7% of your body weight.⁶ This level of weight loss reduced the onset of type 2 diabetes by 58% in clinical studies.^{2, 6}

DISCLAIMER: Not a substitute for medical advice – All content is for informational purposes only and is not intended to provide medical or nutrition advice or to take the place of medical/nutrition advice or treatment from your doctor or health professional. Since each person’s health conditions are very specific, viewers of this content are advised to consult their doctors or qualified health professionals regarding specific health questions. All content, including text, graphics, images, and information in this post/video, is for general information only and does not replace a consultation with your doctor/health professional.

References

1. Li, M., Chi, X., Wang, Y., Setrerrahmane, S., Xie, W., & Xu, H. (2022) Trends in insulin resistance: insights into mechanisms and therapeutic strategy. Signal Transduction and Targeted Therapy, 7: 216. https://doi.org/10.1038/s41392-022-01073-0.
2. Freeman, A.M., Acevedo, L.A., Pennings, N. (2023) Insulin Resistance. Available: https://www.ncbi.nlm.nih.gov/books/NBK507839/. Last accessed: 26 September 2023.
3. Ross, R., Neeland, I.J., Yamashita, S., Shai, I., Seidell, J., Magni, P., Santos, R.D., Arsenault, B., Cuevas, A., Hu, F.B., Griffin, B.A., Zambon, A., Barter, P., Fruchart, J-C., Eckle, R.H., Matsuzawa, Y., & Despres, J-P. (2020) Waist circumference as a vital sign in clinical practice: a Consensus Statement from the IAS and ICCR Working Group on Visceral Obesity. Natura Reviews Endocrinology, 16, 177-189. https://doi.org./10.1038/s41574-019-0310-7.
4. Ludwig, S. (2021) 2^nd Edition: Practical diabetes care for healthcare professionals. Elsevier.
5. Sumner, A. E., Harman, J. L., Buxbaum, S. G., Tambay, A. V., Wyatt, S. B., Taylor, H. A., Rotimi, C. N., & Sarpong, D. F. (2010). The Triglyceride/High-Density Lipoprotein Cholesterol Ratio Fails to Predict Insulin Resistance in African-American Women: An Analysis of Jackson Heart Study. Metabolic Syndrome and Related Disorders, 8(6), 511-514. https://doi.org/10.1089/met.2010.0028.
6. ElSayed, N.A., Aleppo, G., Aroda, V.R., Bannuru, R.R., Brown, F.M., Bruemmer, D., Collins, B.S., Gaglia, J.L., Hilliard, M.E., Isaacs, D., Johnson, E.L., Kahan, S., Khunti, K., Leon, J., Lyons, S.D., Perry, M.L., Prahalad, P., Pratley, R.E., Seley, J.J., Stanton, R.C., Gabbay, R.A. & American Diabetes Asssociation. (2023) Prevention or delay of diabetes and associated comorbidities: Standards of Care in Diabetes – 2023. Diabetes Care, 46(Supplement_1): S41-S48. https://doi.org/10.2337/dc23-S003.
7. Von Frankenberg, A. D., Marina, A., Song, X., Callahan, H.S., Kratz, M., & Utzscheider, K.M. (2017) A high-fat, high-saturated fat diet decreases insulin sensitivity without changing intra-abdominal fat in weight-stable overweight and obese adults.  European Journal of Nutrition, 56(1): 431-443. https://doi.org/10.1007/s00394-015-1108-6.