Sugar highs, exercise and insulin

Sugar highs, exercise and insulin

 

The first episode of the series Trust Me I’m a Doctor dealt with a topic which interests me greatly, the impact of exercise and activity upon our ability to tolerate carbs. The experiment shown focussed upon the effect increasing our baseline level of activity has upon insulin sensitivity. In this post, however, I want to talk about the remarkable ability of resistance training to allow the body to clear sugar from the blood stream even without insulin. This effect has been investigated by scientists because of the potential it offers for diabetic patients to control their condition [1], yet it should be of interest to anyone who, like me, can’t face going super-low carb but wants to maintain high levels of health and performance.

To explain how this works I am going to have to indulge in a bit of heavy science, but if you just want to get straight to my practical recommendations feel free to skip this paragraph. The remarkable power of resistance training to clear glucose from our blood is possible because whilst insulin signals the transportation of glucose into cells it is not insulin which actually transports glucose through the cell membrane. Instead it is structures called GLUTs (which stands for glucose transporters) which, as the name suggests, actually transport glucose from the bloodstream into cells. Of particular relevance to this discussion are GLUT4 and GLUT12, which are the structures which transport glucose into both fat and muscle cells. These structures normally sit below the surface of the cell membrane and are signaled to move to the surface of the cell (translocate) by insulin, but the extreme muscle contractions caused by resistance also cause GLUT translocation [2]. This occurs at the same time as muscle glycogen stores are depleted by the intense exercise. As such resistance training puts the body in the perfect state to absorb glycogen out of the blood even in individuals who are insulin resistant. Furthermore resistance training also increases the concentration of GLUTs in muscle cells, allowing muscles to clear glycogen from the blood at a faster rate, and increases the insulin sensitivity of muscles over time, meaning they absorb glucose preferentially over fat cells. In combination this means that resistance training allows the body to normalise blood sugar levels without the use of insulin, whilst also, over time, increasing the ability of muscles to transport glucose from the blood and decreasing the likelihood that excess carbs will be stored as fat [3]. In short resistance training is incredibly effective at aiding your body to deal with carbs.

 

How then can we use this knowledge? The take home message is that resistance training can have a large impact upon your health. If we combine our new understanding of non insulin mediated GLUT translocation with the conclusions drawn from Trust Me I’m a Doctor we can see that a two pronged approach to the issue of carb tolerance can be highly effective: combining longer periods of light activity with short intense resistance training sessions. Extended periods of light activity, such as walking to work or standing whilst at work, increase insulin sensitivity. Parallel to this resistance training allows your body to deal with carbs whilst your insulin sensitivity returns to healthy levels, and at the same time ensures that carbs are used to fuel muscle cells and not fat cells, keeping you looking and feeling great. If you want to take this a step further I would recommend the strategic timing of your carbs during the day by eating them “inside out” from your resistance training, i.e. concentrating your carb intake to a window centered around your workout, and primarily eating vegetables, fat and protein at those meals furthest from your workout. This means that carbs are readily available when your body needs them but are scarce when your body does not. By understanding the power of carbs and altering your workouts and eating habits accordingly you can cause shocking transformations in both your health and your body composition.

 

For those looking to investigate these ideas further I would recommend exploring the work of John Meadows, and in particular John Kiefer, whose book Carb Back Loading first introduced me to the power of carbs and concepts such as non insulin mediated GLUT translocation.

 

[1] Christ-Roberts CY, Pratipanawatr T, Pratipanawatr W, Berria R, Belfort R, Kashyap S, Mandarino LJ. ‘Exercise training increases glycogen synthase activity and GLUT4 expression but not insulin signaling in overweight nondiabetic and type 2 diabetic subjects.’ Metabolism,’ 2004 Sep 53(9),1233-42.

 

[2] Ivy JL. Role of exercise training in the prevention and treatment of insulin resistance and non-insulin-dependent diabetes mellitus.’ Sports Med, 1997 Nov 24(5), 321-36.

 

[3] Hawley JA, Lessard SJ. ‘Exercise training-induced improvements in insulin action’. Acta Physiol (Oxf). 2008 Jan 192(1),127-35.

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