The food you eat gets broken down into glucose, which then either gets promptly used for energy or gets stored for use later. Insulin is the hormone that directs and manages the glucose in your body. It can direct glucose to 1 of 4 places. Some of these places quickly use the glucose and others store it. The brain is the winner's circle for a glucose molecule but only a small fraction of the body's total glucose makes it directly to the brain.
When glucose is passed over by the brain, it's next preferred destination is the liver. The liver readily uses the glucose for complex molecular bodily function. The liver has limited storage capacity. And over time the liver can begin to ignore the directions of the insulin, also known as insulin resistant (IR), taking in less and less glucose, leaving it in the bloodstream to move on to one of the last two places it can go, the skeletal muscles or to fat cells.
Muscle both burns and stores the glucose. The more a muscle is used, the more glucose it burns and the larger the muscle becomes; allowing it to store more glucose. Therefore, exercise is important to managing diabetes, prediabetes, impaired glucose tolerance, and insulin resistance. Exercise helps to reduce the amount of insulin both the liver and the muscles need to manage the blood's glucose level. The less insulin your body requires, the better.
The last place that insulin can put the glucose in your blood, is into fat cells. And guess what? Your body can make as many fat cells as it needs, and it can expand each fat cell as many as 4 times! Need I say this is the worst option? But statistics show that this is, by far, the most common. Recent data shows that over 70% of Americans over the age of 20 are overweight; with over 37% of those being medically obese. This reflects piss poor management of insulin in epidemic proportions.
It is important to note that if there is glucose present in the bloodstream, the body will not draw on existing fat cells for energy. And when glucose is low the body will prompt you to consume something else to eat for a quick fix. So, while exercise boosts the optimal use and storage of glucose, better managing what you eat is paramount to controlling how well your body uses insulin.