Is Insulin Making You Fat?


In the discussion of things that make you fat, we often hear things like...


"Frequent insulin spikes!"

"Insulin causes fat storage! Without carbs & insulin your body WON'T store fat."

Are these claims true?

Do you really need to be scared of insulin?

You have questions. Today's blog has answers.

What Is Insulin?

Insulin is a hormone produced by your pancreas to help control your blood sugar levels.

When you consume carbs, they’re broken down into glucose.

This glucose then enters your bloodstream (it’s your "blood sugar"), which cues the release of insulin.

Insulin is basically a "shuttling agent" for your blood sugar/glucose - it's what allows the glucose to leave the blood stream, and enter different cells throughout your body for a variety of functions:

1. To be used as energy

2. Stored as liver and muscle glycogen

3. Entering long-term storage as body fat

So, the question is...

Why Are People Scared Of Insulin?

There are generally two primary reasons people believe insulin = fat gain:

1. Insulin is the “shuttling agent” that allows allows glucose to be stored as fat

2. Insulin prevents the breakdown of fat (lipolysis) and increases the formation of fat (lipogenesis)

This has led many to the same conclusion…

"Insulin (and the carbs responsible for spiking insulin) make you fat! A low carb diet that keeps insulin low is a must for fat loss!"

And it would seem they have a valid point, right?

But wait...

Your Body Can Store Fat Without Insulin

As mentioned above, insulin can act as the shuttling agent that allows glucose to enter fat cells, and increases body fat.

This is a common argument for the low-carb diet.

But the reality of gaining body fat is...

Consume carbs → insulin spike → fat gain

...isn't the only way your body accumulates fat.

Even when insulin levels and carbohydrate intake are low, your body can still gain fat.

When debating this same topic, an excellent article by James Krieger says: "There is an enzyme in your fat cells called hormone-sensitive lipase (HSL).  HSL helps break down fat.  Insulin suppresses the activity of HSL, and thus suppresses the breakdown of fat.  This has caused people to point fingers at carbohydrate for causing fat gain.

However, fat will also suppress HSL even when insulin levels are low.  This means you will be unable to lose fat even when carbohydrate intake is low, if you are overeating on calories."

To lose OR gain weight, we still must account for calories.

Personal experience:

My first successful fat loss diet was a low-carb diet.

I had just switched from a high-carb AND high-fat diet (yeah... I was just eating lots of everything).

At the time I thought I lost fat BECAUSE I was avoiding carbs.

(Really, it was because I was restricting my food choices to ground beef and avocados. I was really sick of these foods after a few months, and thus drastically reduced my daily calorie intake.)

That diet actually lead me from this…

…to losing 45 lbs, which culminated in my FIRST EVER shirtless Instagram post:

Lol also, that was a great season of The Bachelor. #teamchad

So after seeing fat loss results, I took my “only carbs make you fat” hypothesis and ran with it to create what I believed to be the perfect diet...


My diet stayed low-carb, but consisted of:

→ 1lb of ribeye, covered in olive oil daily (Seriously. It was great.)

→ Lots of eggs, grassfed butter, and nuts & nut butters, sausage, bacon, and fatty ground beef.

Basically, lots of very calorie-dense foods.

The results still breaks my heart, because I really love ribeye… but yeah I gained a lot of weight back (35lbs):

After a lot of diet trial & error, but I eventually got super lean for multiple photoshoots on a higher carb, lower fat approach:

So what’s the moral of this shirtless story, you ask?


→ I was able to gain fat on a low-carb diet.

→ I was able to lose fat on a low-carb/high-fat diet AND a high-carb/low-fat diet.

Now, I’m not saying that calories are the only thing that matter here - but people get way to caught up in debating carbs vs. fat, and forget to account for calories. Which really make much more difference.

Anyways, back to insulin.

Should We Avoid Insulin Spikes?

So remember when I said...

"Insulin prevents the breakdown of fat (lipolysis), and increases the formation of fat (lipogenesis)."

That in itself seems like a good reason to AVOID spiking your insulin, right?

But... for most of us, insulin levels are only elevated for a few hours post meal. This means your body is always in a flux of fat gain and fat loss. Post meal, you may be gaining fat. But several hours later, you'll be losing fat again as insulin levels come back down.

In a 24 hour period, regardless of carb intake and insulin spikes:

→ If you’re consuming fewer calories than you’re burning, you’ll lose weight

→ If you’re consuming the same amount of calories as you’re burning, weight will stay stable

→ If you’re eating more calories than you’re burning, you’ll gain weight

Once again, calories are the overruling principle that we need to control here.

Another shocking revelation to most people is the fact that...

Protein Also Spikes Insulin



Many high-protein foods stimulate insulin to similar or greater levels than high-carb foods.

Whey protein actually causes a greater insulin response than white bread.

And check out the Insulin Index Of Foods from The American Journal Of Clinical Nutrition:

Cheese, beef, and fish create more insulin release than brown or white pasta, and are on similar levels to brown rice.

This also really pokes holes in the theory that high-protein/high-fat/low-carb diets are more effective due to better controlling insulin.

But interestingly, you don't hear anyone pushing a low protein diet for fat loss.


Maybe Insulin Isn't The Culprit After All?


In fact, research has shown that meals that create a large insulin release are more filling.

This aligns with what is relatively common knowledge for many that have successfully lost a large amount of body fat (and a key component of what I teach my online clients to help regulate appetite) - focusing on including protein at each meal, and fibrous carb sources at most meals is one of the best ways to prevent hunger.

Plus, insulin is a key hormone in building and maintaining lean muscle.

Insulin has an inverse relationship with the hormone cortisol (check out THIS BLOG to learn more about Cortisol). Cortisol is a catabolic hormone - it breaks things down (including muscle) for energy.

An increase in insulin post-workout (ideally through a mixture of protein and carbs), decreases cortisol levels - meaning less muscle protein is being broken down, and your body is in a better position to recover and build more lean muscle.


From today's discussion, we can gather a few basic principles:

→ You need to control calories.

Regardless of the insulin response, carbohydrate, OR fat composition of a meal; you'll gain weight if you eat more calories than you burn in a day, and lose weight if you eat fewer calories than you burn in a day.

Of course it gets more complex than calories in - calories out, as many factors surrounding calories in impact calories out.

But, using my low-carb/high-ribeye diet as an example, we often miss the forest for the trees when it comes to fat loss.

→ It's smart to focus on foods that keep you full, and are hard to overeat.

A big part of why carbs (and insulin) often get a bad rap, is because in our modern environment they often come in the form of foods that make it extremely easy to overeat calories. (Think: hyper-palatable, highly-proccessed "refined carbs").

These food often also contain a large amount of fat, and are very calorie-dense. So while these foods themselves aren't bad, eating lots of calorie-dense foods will make it harder to control your calories as a whole.

That said, for a nutrition strategy to be sustainable long-term, I've found it crucial to teach my online clients how to work foods like this in, in moderation.

And like we know from Mark Haub's Twinkie Diet experiment, you absolutely can lose weight while eating mostly highly-processed foods, as long as calories are controlled. (Again, it'll just make most regulating appetite and getting vital nutrients harder for most of us.)

So for most of us, building our meals mostly around lean protein and fiber (fruits and veggies), and eating primarily whole foods is the surprisingly simple, but effective strategy for building a lean, strong body.


The reality is, we can't blame any one thing - carbs, insulin, fats, etc. for obesity.

A healthy body will use carbs for fuel. But for obese, sedentary individuals, large doses of carbs (or calories in general) are likely going to compound the issue and your body will have more trouble handling all of the insulin.

You are an individual. There is no one exactly like you - you have a physiology and genetics that are 100% unique to you.

This means that when determining what works best for you... it depends.

This is exactly why individualized coaching is such a powerful tool. I've seen client build their leanest, strongest and most confident selves on low-carb diets, high-carb diets, and everything in between.

If you're ready to determine the nutrition strategy that best fits you as an individual, CLICK HERE NOW to apply for Online Coaching.

About The Author

Jeremiah Bair is a certified nutrition coach, strength coach, and owner of the online coaching business Bairfit. Check out his Instagram and Podcast for more applicable strategies for building your leanest, strongest, and most confident self.

Keep Learning

The Fat Loss GuideProject type

Thyroid Health 101Project type

How To Get Toned ArmsProject type

Fix Your Back PainProject type

How to get AbsProject type