What are sugars starches and fiber called?

December 6, 2025 •

3 min read

According to the Cleveland Clinic, all three—sugars, starches, and fiber—are known as carbohydrates, a primary macronutrient essential for bodily functions. While all are fundamentally carbs, they differ significantly in their chemical structure, how the body processes them, and their overall impact on health.

Quick Summary

Sugars, starches, and fiber are collectively called carbohydrates, vital macronutrients found in many foods. These different forms vary in complexity and how the body breaks them down, affecting energy levels and digestive health.

Key Points

Collective Name: Sugars, starches, and fiber are all different types of carbohydrates.
Simple vs. Complex: Sugars are simple carbohydrates, while starches and fiber are complex carbohydrates.
Energy Source: Sugars provide quick energy, while starches offer a more sustained release of energy.
Indigestible Fiber: Fiber is a complex carbohydrate that the body cannot digest, making it essential for digestive health.
Healthy Choices: Prioritizing complex carbs like whole grains and vegetables over simple, added sugars is crucial for a healthy diet.
Sources Vary: Sugars are found in fruits, milk, and sweets; starches in grains and vegetables; and fiber in plant-based foods.

Sugars, Starches, and Fiber: All Parts of a Carbohydrate

At a fundamental level, sugars, starches, and fiber are all different forms of carbohydrates. Carbohydrates, along with fats and proteins, are one of the three main macronutrients that provide energy to the body. Their primary role is to supply the body with glucose, which is used for energy, particularly for the brain and muscles. However, not all carbohydrates are created equal, and understanding their differences is key to a healthy diet.

Sugars: The Simple Carbohydrates

Sugars are the most basic form of carbohydrates, also known as simple carbohydrates. They consist of either single sugar units (monosaccharides) or pairs of sugar units (disaccharides).

Monosaccharides: These are the simplest sugars and include glucose, fructose (fruit sugar), and galactose (milk sugar). They are absorbed quickly by the body.
Disaccharides: These are formed when two monosaccharides are joined. Examples include sucrose (table sugar), lactose (found in dairy), and maltose.

Because of their simple structure, sugars are rapidly digested and absorbed, leading to a quick rise in blood sugar levels. They provide a fast source of energy but are often found in processed foods and drinks, which can contribute to weight gain and other health issues if consumed in excess.

Starches: The Complex Carbohydrates

Starches are made of long chains of glucose units linked together, making them complex carbohydrates. Unlike simple sugars, starches take longer for the body to break down.

Structure: Starches are polysaccharides, meaning they are composed of many sugar molecules.
Digestion: The digestive system must first break down the long chains of glucose into single glucose units before they can be absorbed into the bloodstream. This slower process provides a more sustained release of energy and a more stable blood sugar level compared to simple sugars.
Sources: Common sources of starches include vegetables like potatoes and corn, grains such as rice and wheat, and legumes.

Fiber: The Indigestible Carbohydrate

Fiber is a unique type of complex carbohydrate because the human body cannot break it down and absorb it for energy. It passes through the digestive system largely intact, but plays a crucial role in health.

Soluble Fiber: This type of fiber dissolves in water to form a gel-like substance. It can help lower blood cholesterol and control blood glucose levels. Common sources include oats, beans, apples, and citrus fruits.
Insoluble Fiber: This fiber does not dissolve in water. It adds bulk to stool, promoting regular bowel movements and preventing constipation. Sources include whole-wheat flour, wheat bran, nuts, and many vegetables.

Carbohydrates: Simple vs. Complex Comparison Table

To better understand the differences, here is a comparison table outlining the key characteristics of simple (sugars) and complex (starches and fiber) carbohydrates.


Feature	Simple Carbohydrates (Sugars)	Complex Carbohydrates (Starches & Fiber)
Chemical Structure	One or two sugar units (monosaccharides or disaccharides).	Long chains of sugar units (polysaccharides).
Digestion Rate	Very fast; rapid absorption into the bloodstream.	Slower; require more processing to break down. Fiber is not digested.
Energy Release	Quick burst of energy; can lead to energy crash.	Sustained, steady release of energy.
Effect on Blood Sugar	Rapid and significant spike in blood sugar.	Gradual, more stable increase in blood sugar.
Key Functions	Primary source of immediate energy.	Sustained energy, digestive health (fiber).
Nutrient Density	Often low in essential nutrients; can be considered "empty calories".	Generally high in fiber, vitamins, and minerals.
Sources	Fruits, milk, sweets, processed drinks.	Whole grains, vegetables, legumes, beans.

Making Healthy Carbohydrate Choices

The most important takeaway is to prioritize complex carbohydrates over simple sugars. A diet rich in whole grains, fruits, vegetables, and legumes provides sustained energy, fiber for digestive health, and a host of other essential nutrients. By contrast, excessive intake of added sugars can contribute to weight gain, inflammation, and an increased risk of chronic diseases. Reading nutrition labels and making informed choices about the types of carbohydrates you consume is a powerful step towards better health.

Conclusion

In summary, sugars, starches, and fiber are all known as carbohydrates, but their differences are significant for your health. Sugars are simple carbs that provide quick energy, while starches are complex carbs that offer sustained energy. Fiber is a complex carb that is indigestible but vital for digestion and overall well-being. Making smart food choices by opting for nutrient-dense, complex carbs is the most effective way to ensure a healthy and balanced diet.

MedlinePlus, a service of the National Library of Medicine, provides an in-depth medical overview of carbohydrates and their functions.

Frequently Asked Questions

The primary function of carbohydrates is to provide the body with energy. The body breaks down most carbohydrates into glucose, which is then used as fuel by the body's cells, tissues, and organs.

Complex carbohydrates, like starches and fiber, are considered healthier because they are digested more slowly than simple sugars. This provides a steadier release of energy and helps maintain stable blood sugar levels.

No, the body does not use fiber for energy because it cannot be digested. While some gut bacteria can ferment fiber, it passes through the system largely intact and is important for digestive health.

Yes, many plant-based foods contain a combination of sugars, starches, and fiber. For example, a whole apple contains natural sugars, some starch, and a good amount of fiber.

Simple sugars are rapidly absorbed into the bloodstream, which can cause a rapid and significant spike in blood glucose levels. This can lead to a quick burst of energy followed by a crash.

Good sources of complex carbohydrates include whole grains (oats, brown rice, whole-wheat bread), vegetables (potatoes, corn), legumes (beans, lentils), and peas.

Most starches are considered complex carbohydrates, but some are called "resistant starch" because they are not easily broken down by digestive enzymes. Resistant starch acts more like fiber, promoting gut health.