Do you get energy from nutrients? The science behind your body's fuel

November 2, 2025 •

3 min read

According to the Cleveland Clinic, carbohydrates serve as your body's main and fastest source of fuel. This process, however, is a complex cascade involving several of the essential nutrients you consume, raising the key question: do you get energy from nutrients?

Quick Summary

This article explores how the body extracts energy from specific macronutrients like carbohydrates, fats, and proteins through cellular respiration to create ATP, the body's energy currency.

Key Points

Macronutrients Provide Fuel: Only carbohydrates, fats, and proteins (macronutrients) are used for energy, while vitamins and minerals (micronutrients) are essential helpers but do not provide calories directly.
ATP is the Energy Currency: The energy from digested nutrients is converted into a molecule called adenosine triphosphate (ATP) through a process called cellular respiration.
Carbohydrates are the Body's First Choice: As your primary fuel, carbohydrates are easily broken down into glucose for quick energy.
Fats are for Sustained Power: With more than twice the calories per gram, fats are used for long-term energy, especially during prolonged, low-intensity activities.
Proteins are a Last Resort: The body prefers to use protein for repairing and building tissues, only turning to it for energy when other fuel sources are depleted.
Vitamins are Essential Catalysts: Micronutrients like B vitamins and minerals like iron are critical cofactors that enable the metabolic reactions required to produce energy.

The Three Energy-Yielding Macronutrients

Not all nutrients provide the body with energy. The energy-providing nutrients are the macronutrients: carbohydrates, fats, and proteins. These are broken down during digestion into smaller, absorbable molecules that cells can use to produce energy. While they all provide calories, they differ in energy density and how the body prefers to use them.

The Importance of Carbohydrates

Carbohydrates are the body's preferred source of energy, especially for quick, high-intensity activity. Your body breaks down carbohydrates into glucose, which is then used to fuel your cells. Excess glucose can be stored in the liver and muscles as glycogen for later use. This readily available fuel source makes carbs essential for both physical performance and cognitive function. Complex carbohydrates, found in whole grains, fruits, and vegetables, provide a more sustained release of energy than simple sugars.

The Power of Fats

Fats, or lipids, are the most energy-dense macronutrient, providing 9 calories per gram—more than twice that of carbohydrates or proteins. The body breaks down dietary fats into fatty acids and glycerol, which can be stored in adipose tissue and later used for energy, particularly during prolonged, low-to-moderate intensity exercise. This makes fat an excellent source of stored, long-term energy.

The Role of Proteins

Proteins, made up of amino acids, are primarily used for building and repairing tissues, but they can be used for energy when carbohydrate and fat stores are insufficient. The body's use of protein for energy is considered a last resort because of its vital structural and functional roles. When converted for fuel, amino acids must first undergo deamination, a process that removes the nitrogen group and can place stress on the kidneys.

Cellular Respiration: The Energy Production Factory

The process of extracting energy from nutrients is called cellular respiration, which occurs primarily within the mitochondria of your cells. This is where the energy from glucose, fatty acids, and amino acids is converted into adenosine triphosphate (ATP), the chemical energy currency that powers virtually all cellular activities.

Key stages of cellular respiration

Glycolysis: The initial, anaerobic stage in the cell's cytoplasm where glucose is broken down into pyruvate, producing a small amount of ATP.
Krebs Cycle: Inside the mitochondria, pyruvate is further processed to generate more energy carriers like NADH and FADH2.
Electron Transport Chain: The final stage, which requires oxygen, where the majority of ATP is generated.

The Importance of Micronutrients

While vitamins and minerals do not provide energy directly, they are crucial cofactors that assist the enzymes involved in the energy production process. For example, B vitamins play a vital role in carbohydrate and lipid metabolism, and iron is essential for oxygen transport, which is necessary for aerobic respiration. Without these micronutrients, the energy metabolism pathways would not function efficiently, leaving the body with impaired energy levels.

Comparison of Energy-Yielding Macronutrients


Feature	Carbohydrates	Fats (Lipids)	Proteins
Energy per Gram	~4 Calories	~9 Calories	~4 Calories
Primary Role	Quick and immediate energy source	Long-term energy storage and sustained activity	Building and repairing tissues
Usage Priority	First choice for fuel	Used after carbohydrate stores are low	Last resort for energy
Storage Form	Glycogen (liver and muscles)	Triglycerides (adipose tissue)	Not stored for energy; converted and stored as fat if in excess

The Verdict on Energy from Nutrients

In conclusion, the answer to "Do you get energy from nutrients?" is a resounding yes, but the process is more nuanced than simply consuming food and feeling energized. Your body employs a sophisticated metabolic system to extract and convert chemical energy from specific macronutrients—carbohydrates, fats, and, as a backup, proteins—into the usable cellular fuel known as ATP. This entire process relies on the presence of sufficient micronutrients to function effectively. Understanding this intricate system highlights the importance of a balanced diet for sustained energy and overall health. To delve deeper into the complex relationship between nutrients and metabolic function, authoritative resources such as the NCBI Bookshelf offer comprehensive insights.

Frequently Asked Questions

The primary source of energy for the human body is carbohydrates, which are broken down into glucose for fuel. However, depending on factors like diet and activity level, the body can also rely heavily on fats for sustained energy.

Your body converts food into usable energy (ATP) through a metabolic process called cellular respiration. Digestion breaks down macronutrients into smaller molecules (glucose, fatty acids, amino acids), which are then processed in your cells, primarily in the mitochondria.

Vitamins and minerals, or micronutrients, do not contain chemical energy (calories). Instead, they function as cofactors or coenzymes that help facilitate the complex metabolic processes that extract energy from macronutrients.

Neither is inherently 'better,' as they serve different purposes. Carbohydrates provide quicker energy and are the body's preferred fuel for high-intensity activity, while fats are more energy-dense and are primarily used for sustained energy during low-intensity, prolonged exercise.

ATP, or adenosine triphosphate, is often called the 'energy currency' of the cell. It stores and transfers chemical energy to power nearly all cellular functions, from muscle contraction to nerve impulses.

If carbohydrate intake is insufficient, your body will turn to fats and then protein for energy. This can lead to decreased athletic performance, mental sluggishness, and, if prolonged, muscle wasting, as protein is redirected from its primary building and repair functions.

Yes, protein can be used for energy, but it's the body's last choice. Proteins are first broken down into amino acids, which are then converted into energy only when carbohydrate and fat stores are low.