The Glycemic Index: What It Measures — and What It Doesn't

The Glycemic Index, or GI, is one of the most misunderstood concepts in nutrition. Many people assume that foods with a low GI are automatically healthy or ketogenic, while foods with a high GI should always be avoided.

Unfortunately, nutrition is rarely that simple.

What Is the Glycemic Index?

The Glycemic Index measures how quickly a carbohydrate-containing food raises blood sugar levels after it is eaten.

Foods are typically classified as:

• Low GI: 55 or less

• Medium GI: 56–69

• High GI: 70 or higher

The important thing to understand is this:

The Glycemic Index measures speed, not quantity.

In other words, GI tells us how quickly glucose enters the bloodstream, but it does not tell us how much glucose eventually enters the bloodstream.

That distinction is extremely important.

The Leak Analogy

Imagine a pipe springs a leak in your house.

In one scenario, 500 gallons of water escape over several days.

In another scenario, the same 500 gallons escape in just a few hours.

The fast leak is obviously harder to manage in the moment. Water spreads quickly, damage occurs rapidly, and your ability to react is limited (High-GI foods).

The slow leak gives you more time to respond. You can move furniture, place buckets, and shut off the water before the damage becomes catastrophic (Low-GI foods).

But now imagine a third scenario:

You are away on vacation for a week.

In both cases, you return home to find that the leak continued uninterrupted until all 500 gallons had escaped (Total Carb content).

At that point, the speed of the leak mattered much less than the total amount of water that flooded the house.

The first question becomes:

How fast was the leak?

The second question becomes:

How much water escaped in total?

Both questions matter.

One determines how quickly the body must respond.

The other determines how much glucose the body ultimately needs to deal with.

The Glycemic Index works in a similar way.

• GI tells us how quickly glucose enters the bloodstream.

• Carbohydrate content tells us how much glucose eventually enters the bloodstream.

A Real-World Example

Consider these two scenarios:

• A baked potato has a Glycemic Index of around 90.

• Oatmeal, lentils, and chickpeas all have considerably lower GI values.

Many people immediately conclude that oatmeal, lentils, and chickpeas must therefore be better choices.

From a blood sugar management perspective, that may be true. From a carbohydrate perspective, however, the answer becomes more complicated. Those lower-GI foods may still contain substantial amounts of digestible carbohydrates that eventually enter the bloodstream.

This highlights one of the most important limitations of the Glycemic Index.

So Is GI Useful?

Absolutely.

The Glycemic Index can be a useful tool for:

• people managing diabetes, where slowing the rise in blood sugar can make glucose levels easier to monitor and manage,

• endurance athletes, who may intentionally use rapidly absorbed carbohydrates to provide quickly available energy during short periods of peak athletic performance,

• individuals who experience symptoms such as energy crashes, shakiness, intense hunger, or fatigue following high-carbohydrate meals,

• and healthcare professionals designing meal plans.

However, GI was never intended to be the sole measure of a food's healthfulness.

A food can have a low Glycemic Index and still contain a large amount of carbohydrates.

Likewise, a food can have a high GI but contain very little carbohydrate overall.

Why GI Confuses Keto Beginners

Many low-GI foods still contain too many carbohydrates to fit comfortably within a ketogenic lifestyle.

Food	GI	Keto Friendly?
Chickpeas	Low	No
Oatmeal	Low	No
Brown Rice	Moderate	No
Potato	High	No
White Bread	High	No
Avocado	Very Low	Yes
Cauliflower	Very Low	Yes

The Potato vs Sugar Surprise

A baked potato often has a higher Glycemic Index than table sugar.

• Potato starch rapidly breaks down into glucose.

• Table sugar contains both glucose and fructose.

• Fructose follows a different metabolic pathway before contributing to blood glucose.

This does not mean sugar is healthier than potatoes.

Enter Glycemic Load

Glycemic Load was developed to account for both the speed of carbohydrate absorption and the amount of carbohydrate consumed.

Using our flood analogy, GI measures how quickly the water enters the house. Glycemic Load begins asking how much water is entering the house in total.

What Comfort Keto Watches Instead

Glycemic Load moves us closer to answering the right question, but for ketogenic diets there is an even simpler metric:

How many digestible carbohydrates are entering the body in the first place?

At Comfort Keto, we pay attention primarily to:

• Total carbohydrates

• Fiber

• Net carbohydrates

Food	GI	Net Carbs
Chickpeas	28	32 g
Oatmeal	55	27 g
Cauliflower	15	3 g

The Comfort Keto Rule

The Glycemic Index tells us how quickly glucose arrives.

A low-GI food does not avoid becoming glucose. It simply becomes glucose more slowly.

Carbohydrate content tells us how much glucose arrives.

Both measurements have value. Yet, for ketogenic diets, the total amount of carbohydrate entering the body matters more than how quickly it arrives.

That is why at Comfort Keto, we pay attention to the Glycemic Index — but we pay even closer attention to the total amount of carbohydrates entering the system in the first place.

For most people, understanding how much carbohydrate is being consumed is at least as important as understanding how quickly it arrives.

At Comfort Keto, we do not first ask:

"How quickly will this carbohydrate raise blood sugar?"

We first ask:

"How much carbohydrate is there in the first place?"

Because the easiest blood sugar spike to manage is often the one that never happens.

Thank you for reading, and here's to making informed, confident food choices — one meal at a time.

Wishing you health, great food, and continued success on your low-carb journey,

Chef Janine.