Insulin is a growth factor that tells your cells to take extra glucose out of the bloodstream and store it.
TL;DR: Time when you eat simple carbohydrates around when you’re going to move your muscles. More glucose will be used to fuel your movement and less will be stored. For the extra glucose that isn’t used to fuel your movement, more of it will be stored as glycogen and less as fat.
Metabolism tips to help you store less glucose as fat:
Time when you eat simple carbs around when you’ll be moving.
Eat the amount of simple carbs you need to fuel a workout and to store glycogen after a workout.
Choose foods higher in protein, fat, and fiber that won’t raise insulin levels too much to store less glucose as fat.
Understanding how insulin works allows you to make more informed choices about how to eat to reach your health and fitness goals faster. There is a common misconception that insulin “controls” your blood glucose levels. This isn’t entirely true. Insulin brings down your blood glucose levels (BGLs) when they get too high. Obviously controlling the upper end of your BGLs is really important; elevated BGLs over a series of days sets off a chain reaction of metabolic responses that can end with a coma. This is what happens if a patient with diabetes isn’t able to get proper insulin treatment. So insulin is important in making sure your BGLs don’t stay high for long.
However, your body also exerts control at the other end of the spectrum to make sure your BGLs don’t fall too low. There are two main players that raise your BGLs and release glucose back into the blood: (a) the breakdown of glycogen* (glycogenolysis) and (b) the creation of new glucose molecules from other molecules (gluconeogenesis). Both of these things happen mainly in the liver; in fact, monitoring your BGLs and turning on/off glucose production are two of the main functions of your liver (your muscles also break down glycogen, but they use the glucose for energy in that muscle; they don’t put the glucose into the bloodstream for other tissues to use). (*A reminder that glycogen is extra glucose stored as a chain. It’s starch but for animal cells.)
Insulin is a growth factor. Since you will literally die if your BGLs are too high for too long, your body has a real vested interest in making sure this doesn’t happen. And since everyone goes through periods where we aren’t eating during the day (the longest period being when we’re asleep) and other periods where we are moving and using a lot more energy, your body also has to solve a “cash flow” problem on a daily basis. We have to be able to eat food, use some of it for energy semi-immediately, and store the rest of it for use later. Insulin is a growth hormone that tells our cells to “store this glucose for later”. Which is good news for anyone who likes to sleep without running out of fuel and dying after 40 min.
Your cells can store extra glucose as glycogen or as fat. You need a minimum amount of both glycogen and fat. We rarely see diet fads telling us how to lose that stubborn muscle glycogen, so we’re going to just talk about fat right now. Depending on the person and their athletic condition, healthy body fat percentages are roughly 10-15% for men (21%+ body fat is considered overweight for men) and 10-25% for women (31%+ is considered overweight for women). Fat is the main energy source for cardiac muscle, the circulation of fat is just as well-regulated (though not as straightforward) as the circulation of glucose in the blood, and fat is necessary for healing because all new cells have lipid (aka fat) membranes.
Side rant: Fat is not the problem, inflammation is. Without fat that you either eat or make yourself, you don’t get new cells. Your body would fall apart within weeks because you wouldn’t be able to make new blood cells. Or any other type of cell. But imagine if you just ran out of blood in 3 weeks because you couldn’t make new blood cells. Fat is necessary to stay alive.
The type of fat your body stores may be unhealthy if it causes inflammation or is packed around your organs as visceral fat. But fat itself is not the problem. Inflammation is.
To reduce the amount of new fat your body stores, or increase the amount of glycogen, you need to time when you eat simple carbohydrates with when your insulin levels are low. Wait, if you eat simple carbohydrates but have low insulin, doesn’t this mean your BGLs will go up and there won’t be insulin to tell your cells to take the excess glucose out of your bloodstream?! Isn’t this bad?? It would be bad if you didn’t have another way to get extra insulin out of your bloodstream. Here’s where your muscles come in. Cue the Rocky theme song.
Your muscles will take excess glucose out of the bloodstream without insulin when you move them around. There is always a lag between when you eat simple carbohydrates (which are almost immediately broken down into glucose or fructose) and when your pancreas starts putting out insulin to lower your BGLs. There are also times when your body is less responsive to insulin, so it may be in the blood but most of your body cells won’t be able to use it to get glucose out of the bloodstream. However, your muscles don’t need insulin to take glucose out of the blood. So that lag between rising BGLs and the release of insulin gives your muscles “dibs” on grabbing glucose and using it for energy (instead of storage).
Muscle movement also encourages your body to make glycogen instead of fat. Eating simple carbohydrates about 30-60 min before you move around will help keep your body from storing excess glucose because your muscles will pull that glucose for energy. Your muscles will store more simple carbs as glycogen if you eat simple carbs and protein 30-90 min after you work out. This means moving your muscles not only uses glucose for energy so there is less excess glucose to store, but it also promotes storing glucose after a workout as glycogen instead of fat.
Eating simple carbohydrates when you’re not moving encourages your body to make fat, instead of glycogen. First, the obvious: when you don’t move, your body burns less fuel to make energy. So eating simple carbohydrates when you’re not moving really increases the amount of glucose that is going to get stored. Again, storing fat is fine and normal as long as it isn’t excessive and doesn’t cause inflammation. If we do have some excess fat and we would like to not add more, we can think about when we eat simple carbohydrates and time them around our movement.
Metabolism tips to help you store less glucose as fat:
Time when you eat simple carbs around when you’ll be moving.
Eat the amount of simple carbs you need to fuel a workout and to store glycogen after a workout.
Choose foods higher in protein, fat, and fiber that won’t raise insulin levels too much to store less glucose as fat.
