Having more muscle helps us store less fat, even if we don’t eat less.
TL;DR: Your muscles can help you store less fat by (a) burning more energy and (b) storing energy as glycogen inside the muscle, instead of storing energy as fat molecules inside liver and fat cells. (about 8 min read)
Metabolic tips for using muscles to decrease fat storage:
Move around for 5-15 min after eating so that your muscles will pull glucose out of your bloodstream and stabilize your BGLs.
Skip simple carbs when you’re not moving to keep insulin levels low so that you can actually burn fat when you do start moving.
Add some resistance training to increase your muscles’ ability to burn energy.
Your muscles burn more calories per pound than your other organs. If two people weigh the same, but have different amounts of muscle, the person with more muscle will burn more calories at rest WITHOUT EXTRA EXCERCISE than the person with less muscle. Obviously, you have to put in work to build muscles, but once you have them, muscles offer more buffer against gaining fat because they burn more calories per pound. This is because your muscles can burn energy, store food as glycogen, and can help maintain blood glucose levels (BGLs) without raising insulin levels.
You have probably heard that your muscle tissue is “denser” than your fat tissue. That means a chunk of muscle tissue will weigh more than the same size chuck of fat tissue, because the muscle tissue has more proteins and less stored fat molecules (aka lipids). You know this is true because if you personally went into the kitchen and put a fist-sized serving of cottage cheese on a scale and a fist-sized serving of chicken breast or pork shoulder on a scale, the cottage cheese would weigh less and the meat would weigh more.
Since the meat is denser, it weighs more even though it takes up the same amount of space. (I don’t usually measure cottage cheese by the fistful but not everyone has a scale in the kitchen and can see what 3 oz looks like, whereas everyone has fists that they pick up cottage cheese wi… everyone can visualize how much cottage cheese would fit in their fist…)
Your muscles are built for using energy. Your fat cells are built for storing energy. The structure inside all of your cells that turn stored energy (potential energy) into movement (kinetic energy) is called the mitochondria - if you’ve heard anything about mitochondria, it’s probably that they are “the powerhouse of the cell”. Your muscles’ job is to move, so they have more mitochondria, so you can have more kinetic energy. Your fat tissues’ job is to store energy for later, so fat cells have less mitochondria. More mitochondria = burning more energy.
Your body will store food you eat in two forms: (1) glycogen (aka starch for animal cells) and (2) fat molecules (aka lipids). We actually don’t use the food we eat to power our movement around the time we’re eating; we use the food we ate earlier and stored to power our movement. We use the food we just ate to replace those energy storage supplies. (The exception is when we’re moving fast for a long time; read more about that here). Your body will store food as glycogen first. You can store glycogen in your muscles and liver up to a certain point, and then you store “extra” food you ate as fat.
Having more muscle will help you store energy in your muscles instead of in your fat cells. Here’s where things get fun: when you eat, your muscles are the first line of defense against having high BGLs. Moving around for 5-15 min after a meal will help bring BGLs back down to non-stressful levels and allow you to release less insulin (a growth factor) into the bloodstream. Now, are your muscles using that energy to move during your 5 min stretch break? No. They are breaking down glycogen into glucose to move, and then they are using the glucose they took from the blood to replace the glycogen they just broke down.
More glycogen in your muscles leaves more room for glycogen in your liver. IF, AND ONLY IF, you move around for 5-15 min after you eat, you will first store energy as glycogen in your muscles. If you don’t move, then the glucose in your blood after a meal will get stored as glycogen in the liver, up until a certain point. So to maximize the amount of glucose stored as “not fat”, you want both your muscles and your liver to turn extra blood glucose into glycogen.
More food stored as glycogen means less food stored as fat. Once the liver’s glycogen bin is full, the extra glucose gets stored as fat in the liver. Once the liver’s fat bin is full, the extra glucose gets stored as fat in fat tissue. If your BGLs rose really fast, and your body released a lot of insulin (ie, you ate simple sugars and didn’t move around), then your fat cells will take glucose out of the bloodstream directly and make fat, regardless of what your liver is doing.
To reduce the amount of food we store as fat, we want to increase the amount we store as glycogen - which we can do by moving around for a few min after we eat and by eating foods that don’t cause a fast, dramatic increase in BGLs so that our insulin levels stay low.
You cannot access your energy stores when your insulin levels are high. If you eat and don’t move around, you are relying on just your insulin to bring your BGLs back down to a non-stressful state. If you eat simple carbs that cause a “sugar spike”, you will need to release a lot of insulin to bring your BGLs down, whereas if you eat essential fats and/or fiber and/or protein, you will not cause a “sugar spike” and you will need to release less insulin to bring your BGLs back down to normal.
Since insulin is a growth factor, it tells your body to store more energy and not burn the energy you have stored. Having high insulin levels makes it really easy to make fat and really hard to burn fat; you cannot access your fat reserves to burn for energy until your insulin levels go down.
Keep your glycogen high and your insulin levels low by working your muscles. That’s it. Just move your muscles. You can make the most of your muscles by adding some resistance training (bands, or weights, or moving through water, or wearing a heavy pack and walking uphill, or putting on snowshoes and breaking trail, or turning your bike up to a higher gear, or convincing your partner that you were actually right about that thing from 3 months ago*). Resistance training causes your muscles to make more mitochondria. More mitochondria = burning more energy. So not only can you store more glycogen in muscles when you use them, but you can also burn more energy at rest when you have more mitochondria. Ta da! Now go take a 5 min stretch break.
Metabolic tips for using muscles to decrease fat storage:
Move around for 5-15 min after eating so that your muscles will pull glucose out of your bloodstream and stabilize your BGLs.
Skip simple carbs when you’re not moving to keep insulin levels low so that you can actually burn fat when you do start moving.
Add some resistance training to increase your muscles’ ability to burn energy.
*Sorry, that’s the wrong type of resistance…
Ivy, J.L. et al. (1998). Muscle glycogen storage after different amounts of carbohydrate ingestion. Journal of Applied Physiology.
Christ-Roberts, C.Y. et al. (2004). Exercise training increases glycogen synthase activity and GLUT4 expression but not insulin signaling in overweight nondiabetic and type 2 diabetic subjects. Metabolism.
