High-fructose corn syrup, artificial colors like red #3, and artificial sweeteners like aspartame…

There's a whole laundry list of ingredients that most health-conscious consumers know to avoid. But there's one that often flies under the radar, and it could be lurking in your so-called healthy protein bar: IMOs.

What Is Isomalto-oligosaccharide (IMO)?

IMO is a high-maltose syrup made up of a mixture of short-chain carbohydrates. It is found naturally in some whole foods, but can also be manufactured to be added to packaged products.

In recent years, IMO has become the holy grail ingredient for creating healthy processed foods like protein bars.

It’s often marketed as a sweet-tasting, zero-calorie prebiotic fiber that has essentially zero effect on blood sugar.

Sound too good to be true? Let’s find out...

Why Is IMO Used in Packaged Food?

To say the average American has a sweet tooth would be an understatement. But it’s not our fault: Humans have evolved to seek out sweet, sugary, calorically-dense foods as a quick source of energy. Sugar was rare in ancient times, usually only found in seasonal foods like ripe fruits and honey.

However, in today’s modern processed-food-laden world, sugar-sweetened foods and beverages are literally available on every street corner. Hello, obesity and metabolic disease.

The amount of sugar in most processed food is no surprise to anyone though, right? Luckily, consumers are becoming more well-informed and reading labels, looking for “healthy” options to snack on that are low in added sugar.

Protein bar manufacturers picked up on this need and started creating low-carb, high-protein energy bars. The hidden sweetening agent? You guessed it: IMO.

There are two main reasons why IMO was a seemingly genius addition to protein bars:

  1. It has a sweet taste, but contains fewer calories per gram than natural sugar.
  2. It’s believed to be a source of prebiotic fiber that doesn’t add to the overall net carbohydrate value of a food, making it marketable as “low-carb.”

A solution to the problem of producing a bar that's portable, high in fiber and natural energy – and doesn't taste like sawdust – had seemingly been found.

And as health-conscious consumers, we gobbled these babies up. Finally, a “healthy” bar with a low level of net carbs, relatively low calories, and high amounts of fiber and protein.

However, a deeper dive into the research shows that IMOs might not live up to their sterling reputation as a calorie-free, guilt-free source of dietary fiber.

The Problems with IMO

Most IMO Sources are Not “Natural”

There is no debating that IMO occurs naturally in some foods. However, it is not economically feasible to extract IMO from whole foods on a large scale, so most commercially-available IMO syrups are manufactured from starch using an enzymatic process.

Because of their lower price points, these industrial, starch-based IMO sources are what you will find in the vast majority of the “healthy, low-carb” bars on the market.

Wait… Did we just use “starch” and “low-carb” in the same sentence? Something fishy here…

Industrial IMO Can Spike Blood Sugar

A 2017 study in the Journal of Insulin Resistance aimed to investigate the impact of IMO consumption on blood glucose, insulin and breath hydrogen responses in healthy men and women. The results of the study showed that IMO consumption led to a rise of nearly 50 mg/dL in blood glucose, with a five-fold rise in insulin at 30 minutes.

But that’s not all. Another 2017 study by the Journal of Food Science on IMO clearly stated:

“Analysis of the results with respect to digestibility suggests that the potential glycemic impact of the ingredients and products containing "industrial" IMO may be inconsistent with the product labeling and/or certificates of analysis with respect to overall fiber content, prebiotic fiber content, and glycemic response and are thus inappropriate for diabetic patients and those on low-carbohydrate (for example, ketogenic) diets.”

In other words, IMO does not function purely as prebiotic fiber and has been shown to significantly spike blood glucose in some individuals!

IMO Is Not Zero Calorie

IMO syrup contains about 2.7 to 3.3 calories per gram, and most protein bar manufacturers are using up to 15 grams in one serving to bump up the dietary fiber content. We don’t claim to be math wizards, but we’re pretty sure 15 times ~3 does not equal zero.

IMO Can Cause Digestive Distress

Oligosaccharides like IMO are large molecules that are not fully broken down in the digestive process. This is because the human body doesn’t actually produce the enzyme needed to digest them (alpha-galactosidase), so they can cause digestive distress in many people.

This is especially true for individuals with small intestinal bacterial overgrowth (SIBO) as the undigested oligosaccharide molecules can cause excess fermentation by bacteria residing in the small intestine, resulting in excessive amounts of gas and bloating.

This is also why a low FODMAP diet is often recommended to those with SIBO; FODMAP stands for “fermentable oligo-, di-, mono-saccharides and polyols”. You can thank us during your next Trivia Night.

In other words, if your favorite protein or energy bar is giving you gas, you might want to investigate the label for IMOs (more on that below).

The Difference Between IMO and Inulin

Inulin is another common sweetener or additive in low-carb, low-sugar bars, and how it differs from IMO is a common question.

Inulin, while also an oligosaccharide, is not the same thing as IMO. However, it does have many of the same properties - and downsides - as IMO.

There is some evidence that inulin may not have as deleterious of a blood sugar effect, but because of its ability to also cause severe digestive distress in some individuals, it is definitely not an ideal additive to a “healthy” protein bar.

How to Spot Fraudulent Fiber on a Label

IMO and inulin are sometimes tricky to spot. Here are some terms to look out for when trying to find inulin or IMO on a food label:

  • Fiber (IMO)
  • IMO Fiber (Powder or Syrup)
  • Isomalto-Oligosaccharides
  • Prebiotic Fiber
  • VitaFiber
  • Inulin
  • Chicory root


Here’s a recap: IMO, while marketed as a healthy low-carb, zero-calorie, high-fiber sweetener, is not all its cracked up to be.

In reality, it’s often from unnatural sources, causes blood sugar spikes, gas, and bloating, and is definitely not zero-calorie.

Whether you're an athlete seeking a clean protein bar to fuel a race, an outdoor enthusiast wanting a healthy protein bar, or a parent looking for a wholesome snack for your kids, you're better off steering clear of bars containing IMO.

Instead, opt for products that are made only with whole-food sources and ingredients you’d recognize in nature.

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