Blood Glucose, Insulin, and Performance Sport
The first thing that comes to mind when you mention blood glucose is undoubtedly diabetes. “Monitor blood glucose? I don’t have diabetes,” you’ll say. If you’re truly serious about maximizing your performance, though, it should absolutely be monitored. A blood glucose meter is cheap, and they’re most definitely not just for diabetics. Used wisely, a glucometer can be a useful tool for:
Determining nutrient timing.
Determining TRAINING timing.
Spotting insulin resistance and correcting early, before you end up:
Self-diagnosing a pre-diabetic or diabetic state.s
What is Blood Glucose, how do I monitor it, and why should I care as a physique or performance athlete?
The blood glucose reading number spit out by your blood glucose meter is an indicator of how much glucose (the fully digested, prepared, and ready-for-use-by-the-body carbohydrate) is circulating in your bloodstream. In the US, the measurement is done in mg/dL, or milligrams per deciliter.
If the number is too high (above 100 while fasted), pre-diabetes or diabetes type II is the culprit, and a number of maligned things are happening within your body due to insulin resistance.
The side effects of high blood glucose may begin to set in: pronounced thirst, blurred vision, weight loss (and not in a good way, muscle mass will be the first to go), fatigue, etc.
Your body is not fully utilizing the nutrients that you’re putting into it, causing a buildup of glucose in the blood due to insulin resistance that’s accumulated from a diet too high in carbohydrates.
Now, high blood glucose symptoms aren’t anything to scoff at – but the main thing we’re interested in here from a performance and physique standpoint is the former. Without adequate insulin sensitivity, your body will simply not be able to use the food you eat on-demand to fuel and grow your tissues. This will result in decreased strength, decreased endurance, and decreased muscle mass.
What if it’s high?
If it’s “prediabetic high”, i.e. within the rough range of 101-125, diet and training changes are the recommended course of action.
Reducing carbohydrate intake during periods of inactivity is key. If your levels are high, modify your dietary regimen to keep your carbohydrate intake centered on the periods of time during which your insulin sensitivity would be highest – your periworkout (before, during, and after workout) period. Maintaining a carb-fasted state for the rest of the day will have little impact on performance, and would do wonders for increasing insulin sensitivity.
Resistance training and HIIT, High Intensity Interval Training, are also valuable tools for combating prediabetic insulin resistance as well; and not only will they assist in increasing insulin sensitivity, but they’ll do it in a targeted fashion. Insulin itself is a non-discriminatory hormone, and will shuttle nutrients into any cell (fat or muscle) that is most convenient. Resistance training and HIIT will increase insulin sensitivity specifically in the affected muscle tissues, thus creating an environment where it’s most efficient for insulin to shuttle the consumed nutrients into muscle cells instead of fat. This is ideal for preventing fat storage while maximizing growth.
There is a third, non-pharmaceutical option: glucose disposal agents. These range from compounds as familiar to you as cinnamon to those as foreign as NA-R-ALA, and all of them have different levels of efficacy for different individuals. If an athlete decides to go this route, it’s best to go through this list and test how effective each compound is for you at reducing blood sugar:
NA-R-ALA (Sodium Alpha Lipoic Acid)
*Note, this compound favors glucose storage in muscle tissue over fat tissue.
R-ALA (Alpha Lipoic Acid)
*Note, this also favors glucose storage in muscle tissue
Banaba Leaf Extract
How Does Blood Glucose Throughout the Day Affect Meal/Training Timing?
Meals, resistance training, and cardiovascular training all rely upon the same hormone to dictate optimal timing – Insulin. In a healthy individual, If blood glucose is high, you can be assured that blood insulin levels are also high and the body is primed for protein synthesis. If blood glucose is low, blood insulin levels are likely suppressed as well and the body is primed for lipolysis (burning fat).
According to research done by CG Proud in 2006, insulin is absolutely necessary to activate the pathways necessary to build muscle tissue from amino acids present in the bloodstream. In Guyton and Hall’s Textbook of Medical Physiology, it’s stated simply: “In some unexplained way, insulin ‘turns on’ the ribosomal machinery. In the absence of insulin, the ribosomes simply stop working, almost as if insulin operates an ‘on-off’ mechanism.”
Insulin does have a few other positive effects for athletes:
Insulin prevents muscle tissue breakdown. This creates a much larger net-positive effect on body composition when building muscle, as the body is not fighting against itself to outpace the catabolism typically present during times of extreme muscular exertion.
Insulin shuttles amino acids into damaged muscle cells. As the primary transporter for bloodstream amino acids, insulin is directly responsible for providing the building blocks for muscle repair and growth.
Insulin increases glycogen synthase activity, as well as other key performance enzymes. In doing so, it assists with the storage of glucose in muscle tissues – improving performance, recovery, and overall muscle size.
To be frank, this means that without insulin present in the bloodstream muscle protein synthesis simply cannot occur at all. The key to maximizing growth and progress through resistance training is to ensure that your body has a steady source of glucose (or enough of an excess of protein to convert to glucose through other pathways) before, during, and after exertion. Perform resistance training when blood glucose is elevated.
While resistance training is best done during periods of high blood glucose, the opposite can be said for fat-loss-centric cardiovascular sessions. While performance may suffer due to a lack of ATP created from glucose, the lack of active insulin in the bloodstream will allow for hormone-sensitive lipase to do its job. Normally inhibited in the presence of insulin, HSL is responsible for breaking triglycerides (stored fat) into free fatty acids (“bloodstream” fat) to prime them for burning. Without this mechanism, athletes will not be able to burn fat for fuel during cardio. The takeaway here: when fat loss is a priority, performing cardio in a carbohydrate-fasted state where blood glucose is low is the most efficient way to release and oxidize fat stores.
Moving Forward Without Blinders
Glucose, and indirectly insulin, monitoring is a valuable tool in your arsenal. Through proper measurement and manipulation, you can develop a plan that allows you to optimize body recomposition; the holy grail of physique-centered training. Head out to your local grocery store, stop by the pharmacy, and pick up a glucose monitor ASAP – until you do, your nutrition and training is nothing more than an educated shot in the dark.
Jared Boynton holds a degree in Biochemistry from the University of Tennessee, and is an internet-based performance and conditioning coach and the owner of Genomax Performance Coaching. His experience has been accrued through years of real-world implementation with both his own physique and the physiques of numerous clients. You can contact Jared via email at firstname.lastname@example.org or via his website, www.GenomaxCoaching.com.
Proud CG “Regulation of protein synthesis by insulin.”, Biochem Soc Trans. 2006 Apr;34(Pt 2):213-6.
Liangyou Rui “Energy Metabolism in the Liver”, Compr Physiol. 2014 Jan; 4(1): 177–197.
Hall, John E.; GUYTON, Arthur C. Guyton E Hall Textbook of Medical Physiology. London: Elsevier Editora Ltda.; 2011.