When your blood sugar starts to rise, your pancreas responds by secreting insulin into the blood. Insulin then signals certain cells through an insulin receptor to start moving special proteins into the cell membrane. These proteins are referred to as glucose transporters or GLUT proteins. Some cells in your body do not regulate their glucose uptake and just allow it in freely. These cells are like liver, kidney, brain, and red blood cells. No coincidence that diabetes patients have issues with all those organs. The rest of the cells require the GLUT transporters to get glucose into the cell. In a healthy person, insulin will stimulate GLUT in muscle and fat, but about 70-80% of the glucose will be take up by the muscle tissue because it has more insulin receptors. In a person who has abused carbohydrates, their body will start to create more insulin receptors on the fat cells, making more of the carbohydrate you eat, get stored as fat. For an in depth look, here is a medical break down from Cornell University.
The increase in insulin sensitivity of fat and decrease of it in muscle tissue is why being fat and insulin resistant is a double edged sword. The more fat you have and the more insulin receptors the fat cells have, the harder it gets to lose fat and the easier it gets to store fat. Often times when people lose control of their weight and suddenly gain massive amounts of fat in a short period of time, they have reached a tipping point where they are now storing significantly more glucose as fat without making any major changes in their diet.
Exercise can also stimulate GLUT-4 production in muscle cells that are being worked via a different mechanism independent of insulin. This is why post workout carbohydrates are ok for some people. If however you are a person who has abused carbohydrates and has many insulin receptors on your fat cells, post workout carbs can still be taken up into fat tissue. Charles Poliquin liked to preach that you have to deserve your carbs. This is exactly what he meant. These people may need to minimize carbs consumption until they start to rebalance their insulin sensitivity.
For an overweight person who is insulin resistant, exercise is their best friend. The more physical activity, especially resistance training, the more they can influence glucose being stored as lean muscle mass rather than fat. For diabetics this also takes a significant load off the pancreas, and combined with a low carb diet can start to rehabilitate their pancreas. Increasing muscle mass through resistance training gives your body a better chance at rebalancing insulin sensitivity. Proper weight training can also increase the amount of insulin receptors and the GLUT response in the existing muscle cells pushing the balance even further in your favor.
If you don’t work on correcting insulin sensitivity with exercise and supplementation, diet alone will not always work well enough. Not being able to have any carbohydrates in your diet is not very healthy (discussed in future articles). Switching to just a low carb diet will help, but your body also makes carbohydrates from non carbohydrates sources. Every morning your body releases cortisol to signal your body to start making energy. Part of this process is to start making carbohydrates from protein and releasing stored carbohydrates from your liver and muscle tissue. This is how even without eating carbs you can be feeding fat cells with glucose right out of your own body. So you can see it’s just as important to restore your body’s ability to handle carbohydrates and insulin properly as it is to monitor them in your diet.