Low-Carb and Glycemic Index Basics

Low-carb eating means eating less carb overall. Carbs, short for carbohydrates, turn into blood sugar faster than protein or fat. So the total carbs in a meal shape how high blood sugar rises after eating.

A low-carb plan often cuts back on bread, pasta and sugary drinks. These foods hold a lot of carbs for their size.

A slice of bread, a bowl of rice and an apple sit on a tray beside a tally board for the meal. Bread is marked first and adds two carb tokens to the tally. Rice adds three more, then the apple adds two more, until the tally shows how the carbs add up across the whole meal.

The glycemic index ranks foods by how fast they tend to raise blood sugar. It compares each food with pure glucose, a simple sugar.

A score of 55 or below is low. A score of 56 to 69 is medium. A score of 70 or above is high.

White bread breaks down fast. Lentils and barley release sugar more slowly, thanks to their fiber.

Two lanes race to a blood vessel. White bread on the refined lane sprints to the finish in one dash and drops three sugar pieces into the blood at once. A bowl of lentils on the whole lane only jogs halfway at first and arrives later with one piece.

Low-carb and glycemic index eating are not the same. They overlap, but they measure different things. One looks at how much carb a person eats. The other ranks foods by how fast they raise blood sugar.

Both have been studied. Results differ for each person, so neither is a one-size-fits-all rule. A doctor or registered dietitian can help decide which approach fits.

Key takeaways

• Low-carb eating focuses on how much carb is eaten.
• The glycemic index ranks foods by how fast they tend to raise blood sugar.
• Low-carb eating and the glycemic index overlap, but they are not the same.

Try it

Read the Total Carbohydrate line on one snack or drink you buy, then note it for the next visit.