The evil insulin fairy. The favourite goto mythical being of so many gurus, experts and general douchebags in the health and fitness industry.

To me these people appear to lack the integrity and morals that the industry is so desperately crying out for. With such huge social media following most of them have a platform that can be used to actually educate people. To teach them about the things they really need to worry about. The things that matter. But they don’t. They teach nonsense. Nonsense that has been debunked on numerous occasions. Step forward the Insulin Fairy and her hypothesis.

The Insulin Hypothesis is basically what low-carb zealots base their argument round. It is how they reason that low-carb diets are superior to every other diet. But before I break down what the hypothesis is, it’s probably wise to explain what insulin is, and what it actually does.

Insulin 101
Insulin is a hormone that is released by the pancreas when we eat. It basically regulates the levels of sugar in our blood. When we eat a meal the carbohydrate in our food is broken down into glucose. The glucose then enters our blood. Upon this happening our pancreas senses the increase in glucose and releases insulin. Insulin then acts to allow the glucose to enter our liver, muscle and fat cells. Once the glucose levels in our blood start to come back down, the insulin levels start to come back down. This whole process occurs every single time we eat a meal.
You eat a meal, glucose goes up, insulin goes up, glucose comes down, insulin comes down. Perfectly demonstrated by this chart courtesy of James Krieger.

Something else to make a note of with regards to insulin is that it also stimulates muscle protein synthesis (the building of muscle), inhibits the breakdown of fat and stimulates the creation of fat. But anyway back to the hypothesis.

So what is the Insulin Hypothsis?
The low carb zealots argue that insulin stimulates the creation of fat. They argue that if you consume a high carbohydrate diet that in turn will cause you to gain fat, and all because of insulin.
Their simple reasoning for it is as follows:

They use this same logic to propose that low carbohydrate diets are best for weight loss because the insulin levels are kept lower.

This is the basic reasoning behind the Insulin Hypothesis. But it’s flawed. It’s flawed for a number of reasons. Three fairly straight forward ones, which I will now discuss.

Reason 1
Your body will store fat even when insulin is low [1]. Insulin acts as a suppressor of an enzyme called HSL (hormone-sensitive lipase). HSL works by breaking down fat. But if insulin suppresses HSL this means that the breakdown of fat is also suppressed. So in essence even if you consume a low carbohydrate diet, as the zealots suggest, you will still not lose any weight/body fat if you over consume calories.

Take Home Point: If you over consume calories, even on a low-carb diet, you won’t lose any weight. To lose weight you need to eat fewer calories than you expend. It’s nothing to do with insulin and more to do with calories.

Reason 2
To gain weight you need to be eating in a surplus, in other words you consume more calories than you are burning. Therefore using the insulin hypothesis it would suggest that a high carbohydrate diet would increase hunger, or as the zealots would tell you, insulin increases hunger.
However it’s been shown numerous times that there is no relationship between insulin and feelings of hunger [2]. In fact, high carbohydrate meals have been shown to alleviate feelings of hunger [3]. So even though high-carb meals may have a greater insulin response they are often associated with short-term appetite regulation and increased feelings of fullness in healthy individuals [4].

Take Home Point: Whether you are on a high-carb diet or low-carb diet if you over consume calories you will gain weight. It’s nothing to do with insulin and more to do with calories.

Reason 3
Carbohydrates aren’t the only macronutrient to stimulate an insulin response. Protein is shown to be just as potent as carbohydrates for increasing insulin levels [5]. This fairly recent paper compared two meals with matching calories and the effect they both had on insulin. One meal contained 21g of protein and 125g of carbohydrate (high-carb) and the other meal contained 75g of protein and 75g of carbohydrate (high protein). The blood sugar response was higher in the high carb meal, which follows along with the insulin hypothesis. If you remember…

Eat a meal, glucose goes up, insulin goes up, glucose comes down, insulin comes down

However, the insulin response was slightly lower in the high carb meal when compared to the high protein meal. Showing that protein is just as powerful as carbohydrates at stimulating an insulin response.

Take Home Point: Regardless of whether you consume a high-carb/low protein diet or a low-carb/high protein diet you will stimulate an increase in insulin. So instead of worrying about how high your insulin levels are, worry about whether your calorie intake is matching your goal.

So why are low-carb diets so popular?
Low carbohydrate diets are popular because they can often lead to greater weight loss, but this weight loss has absolutely nothing to do with insulin, unlike what the low-carb zealots will tell you.
Among other reasons like water weight loss, low-carb diets often lead to an increase in protein intake, which is associated with greater feelings of fullness in a lot people. This means people on low-carb diets may find it easier to eat fewer calories, and if you can adhere to a diet on fewer calories guess what happens?

You somehow miraculously lose weight. Science.

Insulin isn’t the bad guy then?
No. Insulin is not this fat producing, appetite hell raising devil hormone that should be kept as low as possible. It is an important hormone for regulation. It’s one of the main reasons that protein is associated with helping to reduce hunger.
The last thing you really should be worrying about is your insulin level. As I’ve already mentioned you should be worrying more about finding a diet that works best for you and your goals, whether it’s weight loss, weight gain, or maintaining a healthy weight. Find a diet that you can adhere to and keep an eye on those pesky calories as they actually do matter.