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What is insulin sensitivity?
Insulin sensitivity is the relationship between how much insulin is required (released) in the body to store a certain amount of glucose. In other words, it refers to how sensitive the body’s cells are in responding to insulin.
Before I lose you, let’s take it a step back. Insulin is a hormone that helps us control the levels of glucose (i.e., sugar) in the bloodstream. If someone has low insulin sensitivity, then their cells to do not store as much glucose as they have a resistance to the action of insulin. This can be a problem, because less glucose being stored or absorbed, means more is floating in the bloodstream leading to chronic high blood sugar levels.
High blood sugar levels all the time is not what we want, because it is associated with a host of negative health outcomes, plus if it is not managed, it will progress to type 2 diabetes (meaning we may have to depend on exogenous insulin injections to maintain stable blood sugar levels).
High insulin sensitivity means we have efficient storage of nutrients (glucose) after feeding, preventing our blood sugar levels from staying high all the time. It also means we need to produce less insulin to have the desired absorption of nutrients. Those with high insulin sensitivity (i.e., like athletes) also tend to partition a greater portion of their ingested nutrients towards lean tissues as opposed to fat depots.
So, we know high insulin sensitivity is healthy and conducive to optimal body composition, we also know poor insulin sensitivity can set us on a path towards metabolic illness. Can we change it? And if so, how do we do it? I answer these questions in the next paragraphs.
How can I improve my insulin sensitivity?
The sensitivity to insulin varies substantially between individuals and can change according to a number of lifestyles, dietary, and even supplemental factors.
1. Body composition plays a role
Ultimately, the higher body fat percentage you are, the greater you are at risk of developing insulin resistance. This explains the common observation of the development of type 2 diabetes among individuals with obesity. So, the easiest way to improve your insulin sensitivity is to drop some kilos from body fat. As a general rule, it is advisable to remain below 20% body fat for a male and 30% body fat for a female to reduce the risk of development of insulin resistance. But, if you can go leaner than that, your insulin sensitivity will continue to improve too!
To reduce the risk of developing insulin resistance it is advised to remaining below 20% body fat for males and 30% body fat for females.
2. Keep up your cardio fitness
Cardiovascular (or aerobic) exercise has a unique ability to improve insulin sensitivity immediately, by increasing the uptake of glucose into cells and subsequently reducing blood sugar levels. Significant chronic changes in insulin resistance have been observed with as little as 25 minutes of brisk walking twice weekly.
On the flip side, as little as 2 weeks of sedentary behaviour (‘couch potatoness’) can drastically reduce insulin sensitivity. The exciting thing about aerobic exercise is that it actually improves insulin sensitivity independent of weight loss.
By incorporating regular aerobic training, you essentially kill two birds with one stone by receiving the independent insulin sensitising benefits from the cardio, plus the extra benefits from the weight loss that the cardio is likely to cause! Consistent, regular cardio training is one of the best ways (second only to weight loss) for improving insulin sensitivity.
Cardio training is one of the best ways to improve insulin sensitivity.
3. Resistance training can boost insulin sensitivity
For the gym junkies I have good news, strength/weights training also improves insulin sensitivity. In fact, there seems to be a relationship between the amount of sets performed and the level of training intensity, with the magnitude of insulin sensitisation. So, train long and hard (within reason) for the best results.
The mechanism explaining the benefits of weight training is likely because this method of training increases muscle mass while also improving the contraction properties of that muscle, so it is better at up taking glucose from the blood. For the body builders out there, this is a huge reason to have high insulin sensitivity, as it will result in more nutrients passaged to your muscles to support growth and fullness!
Increasing your insulin sensitivity through resistance training will helps to support muscle growth as more nutrients is able to enter the muscle.
4. Supplementation may help alongside good diet and exercise
There are a number of supplements available that do induce insulin sensitising effects. However, it must be noted that these supplements cause less of a response in comparison to exercise and weight loss. With that said, if you are already lean and exercising regularly, supplements on top might just be able to earn you a couple of extra percent.
Supplements may help provide an added little boost to improve your insulin sensitivity however they shouldn’t be solely relied on as they work best in conjunction with good nutrition and exercise.
Supplements that may help improve to improve insulin sensitivity
As stated above, supplementation can help unlock a few extra percent when all the other requirements are met I.e. low body fat and frequent cardio/resistance exercise. Here is a list of supplements that can help improve insulin sensitivity as well as their effectiveness at doing so.
In at least four studies, Carnitine has been shown to improve insulin sensitivity modestly. Excitingly, positive benefits have been seen in healthy lean females. Typically, most of the improvements in insulin sensitivity are only observed in unhealthy populations with overweight or obesity. It is thought that carnitine may facilitate glucose deposition into tissues.
Resveratrol is known for its presence in wine, and well renowned for its protective effects on heart and blood flow, but also for improving insulin sensitivity! There appears to be an increase in insulin sensitivity following consumption of resveratrol at low doses (even achieved via wine consumption) among both healthy and overweight people.
Green tea extract
Green tea extract is a mixed bag. Some studies have shown insulin sensitising benefits, some have not. From the studies that do show a benefit, it is mostly in unhealthy persons with severe insulin resistance. So, the more resistant you are to insulin, the more green tea extract might help you. For most healthy athletes, it’s probably not going to do too much.
Another mixed bag, with research showing a very inconsistent effect on insulin sensitivity. Some studies do suggest chromium may increase insulin sensitivity in diabetic persons to a mild degree, but for people without clinical insulin resistance, it doesn’t appear to do much.
Alpha-lipoic acid does have a number of noted health benefits in the research, namely improved blood blow, inflammation and oxidation status. However apart from a minor reduction in HbA1c (indicator of blood sugar levels), it has not been shown in the research to improve insulin sensitivity yet.
Apple cider vinegar
ACV is a heavily promoted insulin sensitiser. Unfortunately, again, the research is a little murky. Some studies have shown a minor decrease in blood sugar levels (indicative of potential insulin sensitising improvements) and a reduction in insulin after meals (meaning less insulin required for storage of nutrients) but improvements in actual insulin sensitivity are inconsistent, with some studies showing modest improvements, and some showing nil.
It’s in your best interest to maintain a high level of insulin sensitivity. The best ways to achieve this are by maintaining a lean body composition, while performing regular aerobic and weights training. Some supplements might help, but they tend to help the most for people with developed insulin resistance. With that said, if you have the disposable income, educated supplement use (in addition to exercise and diet) could add a minor but heavily sought after advantage for a serious athlete.
Afolayan, A. and Wintola, O., 2014. Dietary Supplements in the Management of Hypertension and Diabetes - A Review. African Journal of Traditional, Complementary and Alternative Medicines, [online] 11(3), p.248. Available at: Dietary Supplements in the Management of Hypertension and Diabetes - A Review.
Hannon, B., Fairfield, W., Adams, B., Kyle, T., Crow, M. and Thomas, D., 2020. Use and abuse of dietary supplements in persons with diabetes. Nutrition & Diabetes, [online] 10(1). Available at: Use and abuse of dietary supplements in persons with diabetes.
Kerksick, C., Wilborn, C., Roberts, M., Smith-Ryan, A., Kleiner, S., Jäger, R., Collins, R., Cooke, M., Davis, J., Galvan, E., Greenwood, M., Lowery, L., Wildman, R., Antonio, J. and Kreider, R., 2018. ISSN exercise & sports nutrition review update: research & recommendations. Journal of the International Society of Sports Nutrition, [online] 15(1). Available at: ISSN exercise & sports nutrition review update: research & recommendations.
Wilcox, G., 2005. Insulin and Insulin Resistance. The Clinical biochemist. Reviews, [online] 26(2), pp.19-39. Available at: Insulin and Insulin Resistance.
About the author
Jackson is a PhD candidate, accredited Sports Nutritionist, and competitive bodybuilder and boxer. He currently works at the School of Human Sciences, where he has completed a BSc in Sports Science and in Exercise & Health, and an Honours in Exercise Physiology. Jackson is also completing his PhD in the field of Nutrition where he is directing the first randomised controlled trial investigating the effects of intermittent vs continuous dieting on fat loss, muscle retention and muscle performance in resistance trained athletes.