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Insulin & Fat Loss - A Benign or Toxic Relationship?

Jordan Smith
Published by Jordan Smith
Last updated: December 21, 2022

I remember a period in my career when there was a witch hunt on fat, and every kind of dietary fat was considered unhealthy.

Today we have a similar trend in fitness, saying carbs which are raising insulin levels, are the main culprit for body fat, weight gain, and diseases.

So, I teamed up with my nutritionist, and we spent hours going through research and literature on the subject to determine if insulin and weight gain are just another misinterpreted relationship like the one some years ago.

These are our findings.

Quick Summary

  • The hormone insulin is important for fat loss since it affects the rate of fat burning through lipolysis and lipogenesis.
  • Still, insulin alone doesn’t make you fat because numerous hormones and enzymes control weight gain and weight loss.
  • Weight gain and weight loss predominantly depend on calories in and calories out - too much consumed will most likely be stored in adipose cells (fat tissue).
A person injecting insulin for diabetes and fat loss

The link between fat loss and insulin is best displayed in the metabolic pathway, where elevated insulin prevents the body from depleting fat reserves.

In simple words - an insulin spike means new fuel is here, so there’s no need to use what’s stored in the fat cells.

See, insulin is a vital hormone that regulates blood sugar and makes muscle and fat cells open to store or use this sugar as energy.

So, when insulin is present in the blood, it tells the body to stop using previously-stored energy (fat) since the new fuel is coming from the outside.

“Insulin knocks on the door” to tell your body that blood glucose needs to be delivered to the cells, first to the liver, muscles, and other cells, to be used for fuel, but then to your fat cells, where it can be stored till later.”

- Dr. Cucuzzella, MD & Author of the book ‘Low Carb on Any Budget’

The most significant insulin spike happens when you eat carbs.

Eating simple carbs significantly stimulates insulin secretion because they are quickly digested, cleaved into glucose, and absorbed into the bloodstream.

Therefore, the logic goes: 

  1. A high-carb meal means blood glucose rises immediately
  2. High blood glucose levels cause increased insulin secretion
  3. High insulin secretion makes the body burn less fat and triggers weight gain

This logic is not full-proof since insulin is not the only agent involved in weight gain, and it doesn’t prevent you from burning the fat completely. However, it does influence the rate your body burns fat in a few ways.

Firstly, insulin inhibits lipolysis, a process that makes the body release stored fat, and that’s why people link insulin spikes with the body’s inability to burn fat [1].

The second reason is that insulin stimulates lipogenesis - a process of fatty acids being stored as fat when the body goes into ‘fat storage mode’.

There’s also a phenomenon called ‘de novo lipogenesis’ (DNL), a process when excess calories and carbs are stored as fat [2].

Does Insulin Make You Fat?

A person preparing a syringe of insulin

No, insulin alone doesn’t make you fat since the mechanism behind weight gain is a complex interplay of enzymes and hormones.

Let’s break it down in some more detail.

Fat Storage

While insulin inhibits lipolysis, other active hormones in the blood, like cortisol, growth hormone, epinephrine, norepinephrine, and glucagon, do the opposite and activate lipolysis [3].

Additionally, while insulin triggers lipogenesis, hormones like leptin, growth hormone, and cortisol slow down this process [4].

The main takeaway is that high insulin production suppresses burning fat for energy when compared to low insulin production, but it won’t completely stop fat loss since it doesn’t act alone. 

Insulin and Hunger

Insulin can provoke cravings, but like with fat metabolism, appetite regulation is a complicated process with many other hormones involved (leptin, ghrelin, amylin) [5].

Furthermore, one study from 2010 showed the opposite, saying the higher the insulin response after a meal, the better feeling of fullness is provided [6].


A person injecting insulin for diabetes and metabolism

As insulin directs fatty acids out of the blood and away from metabolically active muscles to adipose cells, the hypothesis is that it decreases the metabolic rate.

This would suggest that a high-carb diet is bad for metabolism compared to a low-carbohydrate diet which provides fuel for other metabolically active tissues.

But some human studies show the opposite effects.

A meta-analysis from 2017 indicates that daily energy expenditure was 26 calories higher in the high-carb versus low-carb diet [7].

Yet another study from 2018 showed that participants on the high-carb diet lost more fat (by a tiny amount) than those on the low-carb diet [8].

However, we shouldn’t disregard numerous studies that show low-carb diets lead to more significant weight loss.

Reasons may include greater protein intake (which reduces appetite and increases satiety), no highly-processed calories, and higher levels of ketones [9].

Excess carbs, primarily those from highly processed foods, may cause a poor cell insulin response, leading to chronically elevated insulin levels and provoking insulin sensitivity issues that could eventually lead to insulin resistance and even type 2 diabetes.

How to Maintain Normal Insulin Levels?

A person checking for insulin levels

To maintain normal insulin levels, you should follow a healthy lifestyle that includes a balanced diet and physical activity coupled with sound sleep patterns.

As long as you are metabolically healthy and your diet contains primarily whole foods, the carbs will cause no trouble.

Together with physical activity and at least 7 hours of sleep, your insulin should remain balanced and enable you to maintain weight or even lose fat in the long run.

All things considered, you can’t manage your weight without proper calorie intake - excess calories will turn into extra fat, while reasonable calorie restriction will make you lose weight [10].

You should also consider natural fat burning supplements as part of the healthy weight-loss equation, as they contain herbs and nutrients which have been studied for their role in increasing metabolic rate and reducing food cravings.


What Is an Insulin Belly?

An insulin belly is deep abdominal fat, also called visceral fat, that raises the risk of developing insulin resistance and type 2 diabetes. Chronically high insulin causes your body to accumulate fat around your internal organs, and when it becomes inflamed, it can become dangerous.

What Is The Optimal Blood Sugar Level for Fat Burning?

The optimal blood sugar level for fat burning should be relatively stable in the range between 70 and 100 mg/dl. Within this range, your blood sugar is optimal, meaning the insulin won’t be high enough to prevent fat-burning or cause fat-storing, thus giving you enough fuel for exercise.

Make Insulin Work in Your Favor

Insulin currently seems to be the only suspect for fat burning inhibition and weight gain.

But you should question whether the reasons behind not losing excess body fat are perhaps smoking habits, junk food, a sedentary lifestyle, and poor exercise habits.

Becoming more active makes you more sensitive to insulin and speeds up fat loss.

You may further s losing fat with some of the most potent fat burners we tested:

During our testing, the top ones helped our clients burn more calories and eventually resulted in a decent waistline decrease.


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