Tommy's Take by Tommy Pomatico 7/20
Does Insulin Make You Fat?
Insulin stops fat burning. That part is true.
It does not follow that insulin makes you fat. Those are two different claims, and treating them as the same one is one of the most common mistakes in nutrition.
What insulin actually is
Insulin is a storage hormone. It rises when you eat, and it rises most in response to carbohydrate.
Its job is nutrient partitioning: moving glucose into muscle and liver, moving amino acids into muscle, and directing some nutrients to fat tissue when appropriate. Without it, blood sugar keeps climbing and nothing gets where it needs to go.
That is not a malfunction. That is the system working.
Where the confusion starts
When insulin rises, fat oxidation decreases. When carbohydrate is available, the body burns carbohydrate first.
People take that fact and conclude something it does not support.
Not burning fat is a temporary shift in which fuel you are using right now.
Gaining fat is a net increase in stored energy, measured over days and weeks.
These are not the same thing. You can spend hours not burning fat and still be losing fat across the week.
You are always switching fuels
You have two fuel sources available at any moment.
Carbohydrate gets used first when it is present. Glucose cannot stay elevated in the bloodstream — it gets used or it gets stored. So after a meal, carbohydrate oxidation goes up and fat oxidation goes down.
Stored body fat is the reserve. It gets used more heavily once carbohydrate is depleted and insulin falls.
Several hours after eating, carbohydrate runs down, insulin drops, and fat oxidation rises again. This happens every day, multiple times a day, whether you are gaining, losing, or maintaining.
Fat burning is not fat loss
One meal tells you almost nothing.
The number that matters is not what fat oxidation looked like at 1pm. It is what the whole 24 hours added up to, and then what the week added up to.
Fat oxidation being low after breakfast is not a problem if it is high overnight. Storage and release run in both directions all day long. The question is only which direction wins over time.
What actually determines fat loss
Energy balance.
If you take in less energy than you expend over a sustained period, stored body fat goes down. If you take in more, it goes up. Insulin is part of the machinery that moves nutrients around inside that equation. It does not override it.
"But doesn't insulin store fat?"
Yes. And your body also releases fat, continuously, when insulin is low.
Storage happening is not the same as storage accumulating. You store after meals and release between them. Net change over the week is what shows up on your body.
Two people, opposite assumptions
Person A eats no carbohydrate. Insulin stays low most of the day. They also eat 3,500 calories against a 2,800 calorie expenditure.
They gain fat.
Person B eats 300g of carbohydrate a day. Insulin spikes several times daily. They eat 2,300 calories against a 2,800 calorie expenditure.
They lose fat.
Avoiding carbohydrate while eating in a surplus still leaves you in a surplus.
Ask a better question
"Does insulin make me fat?" is the wrong question. It leads to eliminating an entire macronutrient for no return, and usually to worse training performance and worse adherence.
The better questions are:
What is my total intake across the week?
Is that intake above or below what I am expending?
Am I training hard enough to give those calories somewhere useful to go?
Insulin is not the enemy. It is one of the most important hormones keeping you alive, and one of the primary drivers of getting nutrients into muscle tissue after you train.
Control the energy balance. The hormone follows.Does Insulin Make You Fat?
Insulin stops fat burning. That part is true.
It does not follow that insulin makes you fat. Those are two different claims, and treating them as the same one is one of the most common mistakes in nutrition.
What insulin actually is
Insulin is a storage hormone. It rises when you eat, and it rises most in response to carbohydrate.
Its job is nutrient partitioning: moving glucose into muscle and liver, moving amino acids into muscle, and directing some nutrients to fat tissue when appropriate. Without it, blood sugar keeps climbing and nothing gets where it needs to go.
That is not a malfunction. That is the system working.
Where the confusion starts
When insulin rises, fat oxidation decreases. When carbohydrate is available, the body burns carbohydrate first.
People take that fact and conclude something it does not support.
Not burning fat is a temporary shift in which fuel you are using right now.
Gaining fat is a net increase in stored energy, measured over days and weeks.
These are not the same thing. You can spend hours not burning fat and still be losing fat across the week.
You are always switching fuels
You have two fuel sources available at any moment.
Carbohydrate gets used first when it is present. Glucose cannot stay elevated in the bloodstream — it gets used or it gets stored. So after a meal, carbohydrate oxidation goes up and fat oxidation goes down.
Stored body fat is the reserve. It gets used more heavily once carbohydrate is depleted and insulin falls.
Several hours after eating, carbohydrate runs down, insulin drops, and fat oxidation rises again. This happens every day, multiple times a day, whether you are gaining, losing, or maintaining.
Fat burning is not fat loss
One meal tells you almost nothing.
The number that matters is not what fat oxidation looked like at 1pm. It is what the whole 24 hours added up to, and then what the week added up to.
Fat oxidation being low after breakfast is not a problem if it is high overnight. Storage and release run in both directions all day long. The question is only which direction wins over time.
What actually determines fat loss
Energy balance.
If you take in less energy than you expend over a sustained period, stored body fat goes down. If you take in more, it goes up. Insulin is part of the machinery that moves nutrients around inside that equation. It does not override it.
"But doesn't insulin store fat?"
Yes. And your body also releases fat, continuously, when insulin is low.
Storage happening is not the same as storage accumulating. You store after meals and release between them. Net change over the week is what shows up on your body.
Two people, opposite assumptions
Person A eats no carbohydrate. Insulin stays low most of the day. They also eat 3,500 calories against a 2,800 calorie expenditure.
They gain fat.
Person B eats 300g of carbohydrate a day. Insulin spikes several times daily. They eat 2,300 calories against a 2,800 calorie expenditure.
They lose fat.
Avoiding carbohydrate while eating in a surplus still leaves you in a surplus.
Ask a better question
"Does insulin make me fat?" is the wrong question. It leads to eliminating an entire macronutrient for no return, and usually to worse training performance and worse adherence.
The better questions are:
What is my total intake across the week?
Is that intake above or below what I am expending?
Am I training hard enough to give those calories somewhere useful to go?
Insulin is not the enemy. It is one of the most important hormones keeping you alive, and one of the primary drivers of getting nutrients into muscle tissue after you train.
Control the energy balance. The hormone follows.
