Why Is Added Sugar Bad For You?
Keto Beginners Series

Why Is Added Sugar Bad For You?

#1 Low Carb & Keto Diet App Since 2010

Track macros, calories, and access top Keto recipes.

Download on the App Store
Get in on Google Play

Why Is Added Sugar Bad For You?

Posted 3 years ago

Brian Stanton

Brian Stanton


Ari Magill, M.D.

Ari Magill, M.D.

Scientific Reviewer

Expert Approved

Most people know that too much sugar is bad for you. Fewer people know the details of why and how sugar makes us sick.

The first problem is that people are consuming sugar at astronomical rates. According to the Dietary Guidelines Advisory Committee of the US Government, the average American consumes about 15 teaspoons of added sugar per day, mostly from sugar-sweetened beverages.[*]  

This sugar frenzy is fueling the obesity and diabetes crisis. Obesity and type 2 diabetes, in turn, increase the risk for many other chronic diseases. 

Can we reverse these problems? With increasing awareness of sugar’s harms, it’s possible to make a difference. This article is part of that effort. 

Read on to learn why sugar is not your friend, plus a few practical tips on how to swap out the added sugar in your diet for more health-supportive options.

Sugar 101

Sugar is a term like sports. It can mean many different things. 

Sugar may refer to:

  • Glucose
  • Fructose
  • Galactose
  • Sucrose
  • High fructose corn syrup
  • And many other molecules

Let’s narrow the scope to “added sugar”, also known as “refined sugar”. When someone talks about added sugar, they’re usually talking about sucrose or high fructose corn syrup.

Both sucrose and high fructose corn syrup are blends of the simple sugars glucose and fructose. Glucose is the main component of starchy carbs, and fructose is responsible for the sweetness of fruit.

Humans have trouble resisting the sweet taste of fructose. Why? Thank evolution. 

Millions of years ago, putting on fat was a good thing. Body fat insured us against the periods of deprivation that were sure to come. 

Fructose, which is rapidly converted to fat in the liver, helped us build this insurance. In other words, enjoying fructose-rich fruits (like figs) conferred a survival advantage.[*] Is it surprising we like how they taste?

On top of that, the creatures with an enhanced ability to store fructose as fat were more likely to pass along their genes. We evolved from these creatures.[*]

But what was once an advantage is now a disadvantage. A fig tree is now in every refrigerator, and that’s bad news for our collective metabolic health.  

Sugar and Insulin Resistance

If you want to understand why sugar is making us sick, you need to understand a phenomenon called insulin resistance. This problem—which may affect up to 88% of Americans—is at the heart of type 2 diabetes, obesity, and many other conditions.[*

Insulin resistance describes the inability of the hormone insulin to effectively manage blood sugar. This means that insulin is unable to store excess blood sugar in muscle and liver cells, and blood sugar stays elevated longer than it should.[*

And when blood sugar stays elevated, more insulin gets released to handle it. Lots more. Because of this, the first sign of insulin resistance is often hyperinsulinemia, or high insulin levels. 

Eventually, however, even large amounts of insulin can’t handle the elevated blood sugar. And then you have both elevated insulin and elevated blood sugar. When this situation gets bad enough, it’s called type 2 diabetes. 

Many things contribute to insulin resistance—including poor sleep—but perhaps the most obvious driver is excess sugar consumption.[*

“An overabundance of sugar in the bloodstream, throughout the day and after many months, erodes the body’s ability to respond to insulin, a state known as insulin resistance,” write the authors of a 2021 editorial published in the Clinical Journal of Sports Medicine.[*]  

Put another way: Consuming tons of added sugar overworks your blood sugar boss— (that’s insulin!)—and then the boss can’t perform. 

Health Conditions Linked To Excess Sugar Consumption

Excess sugar consumption is linked to many nasty conditions. If you’re looking for reasons to cut back on sugar, review this list occasionally.

#1: Obesity and type 2 diabetes

Obesity and type 2 diabetes are closely related. Both problems are rooted in insulin resistance, and both spiral into chronically high blood sugar, high blood pressure, high insulin, and fat gain.

The link between sugar and obesity is fairly straightforward. The more sugar someone eats, the more weight they gain.[*] Not only is sugar easy to overeat, but it also drives hyperinsulinemia, which in turn promotes fat storage. 

Insulin resistance is also central to type 2 diabetes, a metabolic disorder that affects 1 in 10 Americans.[*] One study on over 50,000 women found that consuming one sugary beverage per week (vs one per month) correlated with an 83% higher risk of developing type 2 diabetes over eight years.[*]

#2: Heart disease

Heart disease is the number one cause of death globally. It’s also the number one cause of death in type 2 diabetics.[*

Being type 2 diabetic (or prediabetic) means having high blood sugar, high blood pressure, high triglycerides, high LDL cholesterol, low HDL cholesterol, and a large waistline. All of these are heart disease risk factors. 

Sugar isn’t helping. For each sugary beverage consumed per day, a person’s risk of heart disease may rise 10 to 20%, according to a 2018 analysis published in the journal Nutrients.[*]  

#3: Cognitive impairment

Two quick indications that sugar is bad for cognition: 

  1. Observational data suggest that higher sugar intakes are linked to higher rates of cognitive decline.[*
  2. In the lab, administering a sucrose or glucose solution was shown to impair mental performance on three well-validated tasks.[*

#4: Cavities

It’s been shown that when children consume more sugar, they develop more cavities.[*] Why? Probably because consuming sugar promotes the growth of Streptococcus mutans and Streptococcus sobrinus, bacteria linked to tooth decay.[*]

#5: Cancer

The link between sugar and cancer in humans is far from clear, but one review did find elevated cancer risk (23 to 200%) in 8 of 15 studies looking at sugary beverage consumption.[*] The Warburg Effect (the tendency of cancer cells to prefer sugar as fuel) likely has something to do with this. 

Here’s a partial list of other conditions linked to consuming too much sugar:

  • Acute kidney dysfunction and disease[*]; chronic kidney disease is associated with diabetes and high blood pressure brought on by excess sugar consumption[*]
  • Non-alcoholic fatty liver disease[*]
  • Gut microbiome dysbiosis (more pro-inflammatory bacteria)[*]
  • Alzheimer’s disease[*]
  • Chronic inflammation[*]
  • Impaired immune health
  • Depression and anxiety

Okay, you get the idea that too much sugar is bad. The next step is to do something about it. 

Cutting Down On Sugar

Reducing sugar intake isn’t always easy. The packaged foods and beverages that line the shelves in the supermarket are often full of sucrose or high fructose corn syrup. They’re sugar bombs. 

But if we can eliminate these pseudo-foods, we can drastically reduce our sugar intake. Packaged foods out, whole foods in. It’s as simple as that. 

To take things a step further, we should consider a low-carb or Ketogenic diet. Carb restriction has been shown in multiple studies to reverse type 2 diabetes and promote weight loss in obese and overweight people.[*][*

Simply put: A Keto diet appears to be an effective way to lower blood sugar and escape the insulin resistance spiral. 

A note on hidden sugars even on Keto: due to the prevalence of added sugars in almost all processed foods, even on a low carb or Keto diet you’ll want to keep an eye out for products where sugar has been added to “improve” taste, like store-bought sauces and condiments, deli meats, Keto breads, crackers, seasoned pork rinds, and other “Keto” snacks or treats.

As a general rule, if it comes in a package, read the label. If it contains sugar, sucrose, glucose, high-fructose corn syrup and the like, do your best to avoid it.

Making your own food from whole ingredients is always your best bet when avoiding sugar. Make your own Low Carb Tomato Ketchup, Keto Crackers, and hundreds of other condiments, sauces, snack foods and more available with a quick search of the Carb Manager recipe database.

Easy Sugar Swaps

Eating whole, unprocessed foods with no added sugar is, of course, the most straightforward and healthiest solution to combating this “sugar crisis” in your own life.

But it’s also nice to have a treat sometimes, and fortunately there are now many more natural, low-glycemic sugar substitutes to choose from like stevia, monk fruit, and erythritol. Get the lowdown on the best Keto-friendly, low-glycemic sugar swaps here (plus the 3 to avoid.)

Just because you’re going sugar-free, doesn’t mean you can’t enjoy a sweet treat like these Keto Cheesecake Swirl Brownies or Keto Pecan Pie from time to time.

Fighting the Sugar Crisis

To fight the sugar-fueled health crisis, awareness and education are key. 

Knowing that added sugar is bad isn’t enough. We need to start thinking of sugar like cigarettes—as an obvious risk factor for morbidity and mortality. 

Thanks for reading, and please help spread the word by sharing this article with friends and family who could kick the sugar habit too.