Insulin is a hormone that is most known for controlling blood sugar levels.
When we eat food, particularly carbohydrates, our blood sugar levels increase.
As our blood sugar increases, insulin is released to push glucose into cells to be used as energy or stored as fat for later.
Insulin also shuttles proteins and fats into cells too.
In the presence of insulin, lipolysis (the breakdown of fat) is switched off.
Which makes sense, as why would we need to breakdown fat for energy when we have glucose readily available?
As well as the breakdown of fat being switched off, the storage of fat is increased.
This is because insulin shuttles nutrients into cells, including fat.
This leads many to believe that insulin is a part of the problem to as why people can’t lose weight.
The reasoning is that if your insulin is high then you store more fat and simultaneously can’t breakdown fat.
High carb intake = high insulin = fat breakdown switched off = fat storage increased = weight gain = obesity.
Because of insulins relationship with Carbohydrate, this results in many gurus and health “experts” vilifying carbohydrates as the cause of weight gain, and lack of weight loss.
Here’s why carbs and insulin aren’t to blame.
Acute Response
What people forget is that insulin’s effects are an acute response.
Insulin levels are high postprandially (after food intake), and then they come back to a base level.
In the healthy…
This isn’t the case for diabetics, but that’s beyond the scope of this post.
One of its job is to regulate blood sugar levels and it works with its opposing hormone Glucagon to do this.
Glucagon is released to breakdown glycogen and bring blood sugar levels back up when they are low.
This paring is part of your body’s response to being in constant state of flux, working to maintain homeostasis.
Insulin is simply doing its job, and if it didn’t go up after a meal then you’d be in trouble.
Furthermore, when insulin isn’t present, lipolysis (the breakdown of fat) is switched on.
This means that in periods of not eating (i.e., a massive part of your day), fat is being broken down to be used for energy.
As shown in this chart.
The green shows when insulin is high, and therefore the opportunity for fat storage is also high.
The blue shows the opposite when insulin is low and fat breakdown occurs.
As you can see, over the course of day your body is constantly storing and breaking down fat.
Storing Carbs as Fat is Difficult
I’ll tell you a secret.
Storing carbs as fat is difficult.
It’s an expensive process called De Novo Lipogenesis (DNL).
DNL is a pathway which turns excess Carbohydrates to fatty acids, so they can be stored in the body.
Because it’s an energy expensive process, it doesn’t seem to happen all that much and is a minor contributor to fat stores.
A study using 7 days of Carbohydrate overfeeding showed that DNL didn’t occur to any great extent.
What happens instead is that Carbohydrate oxidation increased, and dietary fat was preferentially stored.
You see, your body is very smart.
It knows that fat is easier to store as fat, because it doesn’t need to be broken down and repackaged.
It’s already fat.
Think of it like this.
Let’s say you have a big jug filled with sand, water, and oil.
The sand is protein and sinks to the bottom.
The water is carbs and sits in the middle (for the purpose of this analogy, the water isn’t absorbed by the sand).
The oil is fat and sits at the top.
As we eat more carbs, the water layer gets bigger and pushes the oil over the top.
Overflowing out of the jug.
Whatever overflows out of the jug, is excess energy and must be stored for later use.
Make sense?
The carbs you eat, push the dietary fat you eat to be stored as fat.
That’s not to say we can’t store carbs as fat at all, because De Novo Lipogenesis does work.
It just takes a lot to make it happen, and a calorie surplus is what will really drive that need.
Protein Raises Insulin Too
If carbs are so bad because they raise insulin, then what about protein?
That raises insulin too.
If we’re going to vilify a macronutrient for raising insulin, shouldn’t we do it for protein as well?
Protein is broken down into amino acids which stimulate the pancreas to secrete insulin.
One particular amino acid (Leucine), is a key driver of this and this study shows a direct dose-response relationship
Insulin isn’t just a hormone to balance blood sugar.
It’s also considered an anabolic hormone that acts to build muscle too.
Fat Can Be Stored When Insulin Isn't Present
Fat isn’t only stored when insulin is present.
Insulin isn’t needed for fat storage.
It can be stored by a variety of other means, that all work in conjunction to maintain homeostasis.
One of these is called Acylation stimulation protein (ASP).
When insulin is low, fat can be synthesized and stored by ASP.
Plus, similar to the effects of insulin, dietary fat also suppresses the hormone HSL (Hormone sensitive lipase).
HSL breaks down fat.
So, when HSL is suppressed as we consume dietary fat, less fat breakdown occurs.
So basically, when we don’t eat carbs and insulin is low, fat can still be stored as fat.
And do you know when this occurs?
When we eat in a calorie surplus.
Even if you ate no carbs at all, but 4000 calories of fat like you’re on keto (assuming this is a surplus for you), you would store the excess as fat.
Conclusion
Insulin is a great hormone.
Without insulin you would die.
There are people out there who do anything to be able to have some insulin in their body.
Diabetics are case and point.
I’d bet that all the diabetics you come across would be willing to trade a nice sum of cash for their insulin problems to disappear.
Health gurus, nutritionists, and medical “professionals” like to pick on insulin and carbs as the bad guys.
But it’s incredibly short sighted to think that insulin is the cause of your weight loss problems.
Acute fat storage doesn’t equate to total fat gain if you’re not in a calorie surplus.
If you’re not consuming excess calories, you won’t be storing fat over the long term.
Sure, you will store fat in the short term.
But this will be broken down within the same day/week, as long as you’re not continually in a calorie surplus.
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