Carbohydrates get a bad rap, but in moderation they are OK and will not automatically make you gain weight just by eating a healthy amount of carbs.
The definition of insanity is doing the same thing over and over again and expecting a different result.
First the Atkins diet claimed to be the solution to weight loss and health. It
Can we stop demonizing carbohydrates already?
In a now infamous scene from her documentary “Homecoming,” a dejected Beyoncé reports, “In order for me to meet my goals, I’m limiting myself to no bread, no carbs, no sugar…”
…while eating an apple. Which contains carbs. If you’re going to remove something from your diet, you should probably know what it is first.
Carbohydrates are one of the three main building blocks, also known as macronutrients, that make up all food. Protein and fat are the other two. These macronutrients are essential for the body to function.
Carbs can be further split into three groups:
- Sugars are simple short-chain compounds (monosaccharides and disaccharides) found in fruit like apples and the ubiquitously demonized white sugar. They taste sweet and tend to be highly palatable.
- Starch is a longer chain of sugar compounds (polysaccharides). This type includes things such as bread, pasta, grains, and potatoes.
- Dietary fiber is the odd one out. It’s also a polysaccharide, but the gut can’t digest it.
Remember, almost all foods that people call “carbohydrates” actually contain a combination of all three types of carbs along with protein and fat.
Apart from table sugar, it’s rare to find something that’s purely a carb. That’s just not how food tends to work.
I’m not going to talk about this for very long, because there are hundreds of articles on the internet giving you lists of carbohydrates that you “should” and “shouldn’t” eat, pitting them off against each other like some sort of gladiatorial fight to the death.
I’m not going to do that.
Of course certain foods have more nutrients than others, and yes, the fibrous carbs are going to have the best overall impact on our health.
Can you do me a favor, though? Seeing as food doesn’t have a moral value, can we stop using the words “good” and “bad” when it comes to what we eat?
It’s not helpful, and I’d argue it’s actually harmful to our relationship with food.
It’s possible to recognize the hierarchy of benefit that certain foods have without demonizing others to the extent of exclusion and restriction.
Now let’s get on to the main reason why I felt the need to write this article: Why do people believe that carbs make us fat?
Hypotheses in science are made to be tested. The problem with this particular one is that it’s been falsified (proven incorrect) on multiple occasions — yet those who hold carbohydrates responsible for obesity have all built massive careers off it, and would have much to lose by recognizing that fact.
Money has a habit of ruining objective science.
When we eat carbohydrates, enzymes in our gut have to break down those polysaccharides and disaccharides before our small intestine can absorb the resulting monosaccharides.
After absorption, the subsequent rise in blood sugar stimulates the release of insulin, which enables the cells to take up glucose and use it as an energy source.
Insulin also has the job of signaling the liver to store excess glucose as glycogen. The liver can only store a certain amount of glycogen at one time, so anything extra then gets converted to fat for longer-term storage, also under the control of insulin.
People usually freak out about that last bit, but relax: Fat storage is both normal and essential for proper functioning of the human body. Fat storage, fat breakdown… the whole thing is in a constant state of flux.
Glucose is the most important fuel source for the body. Due to the fact that we don’t eat every minute of the day, there are times when our blood sugar levels need boosting. That’s when the previously stored glycogen gets broken down back into glucose.
Depending on the body’s need for energy, fats and proteins can also be broken down to be utilized for fuel.
As glucose is the brain’s preferential source of energy, there are many mechanisms in place to keep our blood glucose levels stable. It’s a no-brainer (pun intended).
When these mechanisms aren’t functioning properly (in conditions such as diabetes), our health tends to suffer.
Since insulin upregulates fat storage and downregulates fat metabolism, it seemed reasonable to test the hypothesis that if we kept insulin stimulation at a minimum by restricting carbs, it might be easier to mobilize and use fat for energy.
But before it could be tested fully, people started preemptively claiming that low carb diets (originally Atkins, more recently keto) were best for weight loss, and insulin stimulation was the reason for weight gain and obesity.
There are lots of nuances to this hypothesis, with many different elements having subsequently been proven incorrect. But there isn’t time to go into them all in this article.
So, let’s focus on the main one.
In science, a hypothesis becomes proven incorrect when an integral part of it is shown to be wrong.
The theory that insulin stimulation directly causes weight gain can be tested by comparing rates of weight loss between people on a high carb diet and people on a low carb diet (when calories and protein are kept the same).
If the theory is correct, those on the low carb diet should lose more weight due to a lower stimulation of insulin.
The best way to test this out is through utilizing controlled feeding studies. These create a highly controlled environment with participants living and sleeping at the lab for the duration of the study. All movement and food intake is measured and recorded. (I can’t image it’s particularly pleasant for those involved!)
Fortunately for us, this hypothesis has been appropriately tested time and time again over the last 3 decades.
This 2017 research review article by Hall and Guo looked at 32 different controlled feeding studies. The results were outstandingly clear:
When calories and protein are controlled, there’s no energy expenditure or weight loss benefit from eating a low carb diet over a high carb diet.
In the end, weight manipulation comes down to calorie control, not insulin control.
We have a problem in the scientific community, and that problem is identity.
“Low carb” has become part of one’s identity, with the rise of “low carb doctors” and “low carb dietitians.”
Despite all the available evidence falsifying the carbohydrate-insulin hypothesis of obesity, many are unwilling to let go of their dogma and genuinely explore the evidence and their identity.
So, in the end, I think it’s down to the rest of us who haven’t registered our identity yet to a certain way of eating to keep holding up the truth in the face of dogma.
It will take some time, but if we don’t champion critical thinking and good science, what are we left with?
I wanted this article to be a stand-alone, specifically looking at the carbohydrate-insulin hypothesis of obesity.
I know a number of you will have other reasons as to why you’ve been told to eat a low carb diet, and I’ll look at sugar, diabetes, “low carb for health,” and all the nuance that brings another time. Hold tight.
Dr. Joshua Wolrich, BSc (Hons), MBBS, MRCS, is a full-time NHS surgeon in the United Kingdom with a passion for helping people improve their relationship with food. One of the few men in the industry addressing weight stigma and diet culture, you can find him on Instagram regularly combating spurious nutrition information and fad diets while reminding us that there’s so much more to health than our weight. Keep an eye out for his upcoming podcast, “Cut Through Nutrition,” for an in-depth look at the appropriate use of nutrition in medicine.