Do carbs make us fat?
“So carbs…what’s the truth? No bulls**t.”
~ James Molden
We have all probably heard things like “I’ve cut carbs”, “no carbs until marbs”, and “I stopped eating bread and got thin” but where does this idea that carbs make you gain weight and create excess body fat come from?
Well the answer is the carb-insulin model of obesity.
What is that? I hear you ask. Well in short:
You eat carbohydrates
Your body releases insulin
Then, according to the model, insulin 1) keeps your body from burning fat for energy, and 2) drives fat and sugar from your bloodstream into your fat cells
All this makes your body think it’s starving, causing it to slow your metabolism and increase your hunger.
Followers of the carb-insulin model use it as an explanation for why there is a world wide obesity crisis. These same followers apply an over-simplified solution to the crisis...eat a low carb diet! At the same time as reducing obesity you will create hormonal balance and have a metabolic advantage therefore being able to eat as much as you want when you want, without worrying about calories or portions, sound familiar? We all have that one friend.
It takes two to tango - welcome to the floor, Carbs & Insulin.
When you eat certain carbohydrates, such as starch and sugar, they’re quickly broken down into glucose and absorbed into your bloodstream. This raises your blood glucose levels. (Also called blood sugar levels.)
Therefore the more carbs you eat in a meal, the higher your blood sugar levels rise immediately after a meal.
This is where insulin arrives at the party.
In response to this your body wants to regulate and bring your blood sugars into a normal range, which if you didn’t know is 70 -100 mg/dl. Your body wants to maintain this level of blood glucose, to keep you healthy and all systems functioning optimally. That's the job tasked to our friend insulin.
Insulin’s primary task is to move glucose from the bloodstream to the muscles and fat cells to be used as energy or stored for later use. Without this process, blood sugars would stay elevated and cause a number of inflammatory side effects such as damage to your blood vessels, kidneys, eyes, and nerves. This is why diabetes can lead to many health complications.
The short and curlies of it is - when blood sugars goes up, insulin goes up.
Remember the more carbs you eat in a meal the more your insulin will need to go up to then normalise the levels.
However there is always the need for context and the simplification of more carbs means more insulin is also dependant on other factors such as:
Fitness level
Body fat and muscle mass
Genetics
The intensity and length of exercise, and how recent it was
Time of day
What else you’ve been eating - for example, fat and fibre (another type of carbohydrate) can slow the absorption of glucose, blunting the insulin response, while certain proteins can increase the insulin response.
Again to summarise those points - the leaner and more active you are the more your body is able to deal with the moving of glucose from the bloodstream, this is known as insulin sensitivity. The body is more sensitive to the fluctuations in blood sugar, which is why you may have heard that fitter people are able to ‘cope with carbs’ better than sedentary people.
Why can this process lead to problems?
You may have heard the term insulin resistance and this is where the body produces more insulin than is needed to reduce blood glucose to normal levels. This is generally thought to happen when your cells become resistant to insulin, and this insulin resistance is a precursor for type 2 diabetes.
The longer this continues in the body the worse the condition becomes, even leaving insulin levels high when you haven’t eaten anything, this is known as hyperinsulinemia.
We don’t know exactly why insulin resistance happens. It’s mainly thought to be caused by chronically-elevated levels of fatty acids in your bloodstream. There are a number of other factors related to insulin resistance too, such as: genetics, ethnicity, sleep patterns, exercise habits, and smoking.
What we can say is that people who are obese and have high levels of visceral fat surrounding their internal organs are more likely to be insulin resistant.
So do carbs make you fat?
We need to look at two more processes to see why it might be thought that carbs make you fat. As we have established carbs are the primary macronutrient in elevated insulin levels.
One of the processes we are looking at now is called lipolysis (the body’s way of removing fatty acids out of storage and into the bloodstream for energy). It is thought that insulin actually inhibits this process, because levels are high which means fewer fatty acids are available to fuel your muscles and other metabolically active tissues. Because of this, many people equate insulin spikes with ‘turning off’ your body’s ability to burn fat.
Another process is lipogenesis which is thought to be stimulated by insulin. Meaning that fatty acids are moved from the bloodstream into fat cells for storage. Alongside this is the term De novo lipogenesis (DNL) which is where carbs are converted and stored as fat.
What needs to be noted here is that this only occurs when you are consistently eating more than you expend over long periods of time.
All this makes it sound like it is carbs and insulin ‘tango-ing’ together that makes us fat, but it is worth noting that this is one of the body’s many clever hormonal responses to bring about homeostasis. At any given time there is a huge interplay of hormones and enzymes that can counteract, change, limit, or enhance the effects of a chemical, including insulin.
Therefore I would say it is too simple to assume insulin makes you fat and in turn carbs make you fat.
For instance insulin inhibits the moving of fatty acids from cells (lipolysis) to the bloodstream because you have just eaten macronutrients that provide you with energy, mostly carbs and/or protein. It is like going out with £50 in your pocket and then going to the cash point again to pay for £20 of fuel. It is more efficient for the body to use the energy you have just consumed.
Again this ties into prioritising a consistent exercise regime and only eating enough food to sustain this exercise and not body fat.
For instance, while insulin inhibits lipolysis (fat burning), there are other hormones that are active at the same time that stimulate lipolysis:
Glucagon
Epinephrine
Norepinephrine
Growth hormone
Cortisol.
Furthermore, while insulin stimulates lipogenesis (fat storage), other active hormones such as leptin, growth hormone, and acute increases in cortisol, actually inhibit lipogenesis.
It is far too simple to say carbs make you fat!!
SO!! When your insulin levels are high, you’ll burn less fat for energy than when your insulin levels are low. But you won’t stop burning fat altogether. You’ll preferentially burn carbohydrates for energy instead.
The real question is then, does insulin stop you losing fat?
Well that’s simple, only if you are eating more than you require. There is zero scientific evidence to suggest you’ll gain weight if your energy intake is less than your energy expenditure. Insulin itself doesn’t cause weight gain. You also need to eat more calories than you expend.
In healthy people, the increase in insulin after a meal only lasts a few hours as it will then return to baseline, allowing fat burning to start up again. If energy intake is lower than energy expenditure, insulin will stay low for long periods throughout the day and night. This permits fat burning to occur at full effect despite short periods of fat-burning inhibition.
So, if you initiate a diet to lose fat, you can accomplish that with or without carbs. Despite what the simplified carb-insulin model of obesity may say.
What I will add is there is always the case for some individuals to reduce carb intake to alleviate insulin resistance. If you are on a fat loss journey and you are sedentary you may benefit from reducing carb amounts according to your activity levels. Prioritising the quality of carbs will also assist in achieving a healthy life.
Basically, what I am trying to say with all those paragraphs above is...move because you can, eat to nourish the body and mind, and sleep today to thrive tomorrow.