Why Carbs Are Not The Evil People Think They Are

What is “carb tolerance”?

Ever heard someone say, “oh if I eat that one cookie I will gain 5 lbs, because I’m carb intolerant.”? Or notice that certain people can eat carbohydrates for days and days and not seem to gain any weight?

Well this is “carb tolerance” and “carb intolerance”.

Now, is this actually a thing or not?

What does it actually mean?

Maybe “carb intolerant” people eat too many carbs. Or the wrong kind. You know – the processed kinds.

Maybe the problem isn’t the carbs at all. Maybe that “baked potato” you had, may have had too much sour cream or butter than potato.

Then again…maybe some of those people do not process carbs the way others do. In other words, their genes may be to blame.

Genes: Can your genes be the reason you are intolerant to carbohydrates?

This isn’t completely untrue. There is a correlation between obesity and a person’s ability to make amylase, an enzyme that helps to break starch down in your mouth.

But why would this enzyme vary person to person?

This is called genetic polymorphism.

These are natural variations in gene, DNA sequence, or chromosome that show up in behavior or physiology (phenotype).

These are what exactly makes you different from the person sitting besides you. Basically they are what makes you you.

One of these variations are called “Copy Number Variations”. These are polymorphisms resulted from changes to the numbers of the genes. CNVs can create significant differences among people.

For years it was believed there was two copies of genes, now its shown that there can be multiple copies of genes. There can also be fewer than two copies. Up to 12% of our DNA has CNVs. Even identical twins can have different CNVs.

CNVs are also associates with many complex diseases, ranging from Lupus to Crohn’s. CNVs have also been linked to resisting HIV infection.

CNVs may also give us one clue to carb tolerance.

The enzyme amylase

Salivary amylase is an enzyme in. Your saliva that starts the digestion of starch. It’s a well known enzyme that has been known about for years.

The gene that makes up amylase, AMY1, varies in copy number from person to person. And AMY1 genes have a huge CNV range, from two to sixteen copies.

More AMY1 genes mean more salivary amylase.

More salivary amylase means you break down carbs more effectively, immediately.

As soon as you bite into that carb, amylase goes to work.

Again, if you have more AMY1 genes, your carb-digestion works bigger and faster.

Research Question

So what happens if you have fewer AMY1 genes for amylase production and live in a society where it is high-starch diets are the norm?

Basically low CNVs of the salivary amylase gene predisposes you to obesity.

People who have more copies of AMY1 (the gene that makes amylase) have more salivary amylase and lower BMI.

If you have more than 9 copies of AMY1 then you are eight times less likely to be obese compared to someone who has fewer than four copies of AMY1.

In other words, more amylase equals less body weight. And vice versa.


…before you start blaming all of your tendency to gain weight on your genetic inheritance, it’s import to note the total BMI range was only from 25-27.

So while “carb intolerance” may influence your tendency to gain weight, it’s not the only factor involved.


The findings suggest that there really is such a thing as “carb tolerance”.

People with more AMY1 are lucky

Here’s why:

They “naturally” eat less.

More amylase means more digestion of carbohydrates in the mouth; more digestion in the mouth means foods may taste sweeter and feel richer. As a result, people with more amylase might feel satisfied eating less.

Perhaps this also helps explain why eating slowly helps promote more weight loss.

They tolerate glucose well.

Higher levels of salivary amylase correlate to a higher pre-absorptive insulin response, and this is key to glucose tolerance.

Everything’s lower GI to them.

Different amylase concentrations essentially result in different rates of carbohydrate absorption of the same food, or a different glycemic index for each person eating a given food. In other words, the glycemic indexes you see may not be correct for everyone.

What can you do?

While this may sound complicated, there are some simple solutions.

If, based on your genetic inheritance, you think that you may have few copies of AMY1 and may, as a result, have a low carb tolerance, there are a few things that you can do to help:

1) Eat slowly and chew your food thoroughly.

2) Use probiotics

3) Keep eating healthy carbs

Even people on the low end of amylase production still make more amylase than chimps and nearly all other animals.

Chimps don’t eat bread but they do eat carbohydrate rich foods like bananas and you don’t usually see an overweight chimp.

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