Why might our mitochondria function less efficiently?

A decrease in energy is often associated with aging.

However, you can be young and feel like you don't have access to your energy.

Our mitochondria are the small structures inside our cells that help convert nutrients into ATP, a form of energy directly usable by the body.³

To do this work, they need several things: essential nutrients, oxygen, energy substrates, functional enzymes, and signals that allow them to adapt to our needs.

Thus, our ability to efficiently produce cellular energy does not solely depend on our age.² ³

So, what can influence the functioning of our mitochondria - even when we are young?

1. Lack of physical activity

This is probably one of the most important factors - and fortunately, one that we can act upon.

Our mitochondria are extremely adaptable.¹ ²

When we exercise, especially regularly, our muscles receive the signal that they will need to produce more energy.

This notably stimulates mitochondrial biogenesis: cells develop and renew their mitochondrial capacity.¹ ²

Conversely, physical inactivity is associated with a decrease in several parameters of muscular oxidative capacity.¹ ²

Our mitochondria adapt to what we demand of our body.¹ ²

2. Not having enough of certain nutrients

Producing ATP requires a true chain of biochemical reactions.

And each one needs its tools.

B vitamins, magnesium, iron, copper, and several other micronutrients act as cofactors or essential constituents of energy metabolism.

A genuine deficiency can therefore disrupt some of these reactions.

This is an important notion: having enough calories does not necessarily mean having enough of all the micronutrients necessary for cellular function.

This is also why persistent fatigue sometimes deserves to be investigated rather than simply compensated by more stimulants.

3. Lack of sleep

While we sleep, our body does not shut down. Sleep contributes to recovery, metabolic regulation, and the maintenance of our circadian rhythm.⁴

Mitochondria themselves are linked to this biological clock.⁴

Experimental studies show that sleep deprivation can alter mitochondrial metabolism and how the body uses energy.⁴

A night's sleep is therefore not just for resting our brain: it also prepares our metabolism for the next day.⁴

4. Metabolic stress

When metabolism is disrupted for a long time - for example, in the presence of insulin resistance or chronic hyperglycemia - mitochondrial function can also be affected.³

The relationship is complex and works in several directions: mitochondria participate in metabolism, while our metabolic state, in turn, influences their functioning.³

This is why mitochondrial health cannot be separated from overall metabolic health.³

5. Excessive oxidative stress

Producing energy naturally generates reactive oxygen species.³

This is not abnormal.

In controlled quantities, some of these molecules even serve as signals allowing our cells to adapt.

Our body also has remarkably sophisticated antioxidant systems to maintain balance.

The problem arises when a persistent imbalance occurs between the production of these molecules and the body's ability to neutralize them and repair damage.³

This is what is called oxidative stress.³

6. Certain diseases and medications

Some genetic diseases directly affect mitochondria, but other acquired conditions can also alter their function.³

Certain medications can also have mitochondrial effects.

This is an additional reason never to conclude that unexplained fatigue simply means "our mitochondria are not working properly."

Fatigue is a symptom, not a diagnosis.

When it persists or becomes unusual, it is important to investigate the cause.

7. What about age?

Yes, aging is associated with changes in mitochondrial function.³ But age doesn't explain everything.

Some of the changes observed over the years can also be influenced by decreased physical activity, muscle mass loss, metabolic state, and other factors that sometimes accompany aging.² ³

And most importantly, mitochondria retain an adaptive capacity. Exercise can stimulate mitochondrial adaptations even at an advanced age.²

So, can you be young and lack energy?

Absolutely. But that doesn't automatically mean our mitochondria are failing.

A feeling of fatigue can have many causes: insufficient sleep, inadequate energy intake, stress, iron or vitamin B12 deficiency, thyroid problems, infection, medication, sleep disorders, or many other conditions.

That's precisely why we must resist the idea of a single diagnosis. Energy is the result of an entire system.

Mitochondria are a fundamental part of it, but they never work alone.³

What can we do?

The most powerful actions are also the most fundamental: Move. Develop and preserve our muscles.¹ ² Sleep enough.⁴ Eat in a way that provides our body with the energy, protein, vitamins, and minerals it needs.

And when fatigue persists despite everything, seek out why. Because sometimes, our body isn't lacking willingness. It may simply be lacking something it needs to produce its energy.

And this last sentence bridges perfectly with our future article on nutritional deficiencies and symptoms.

References

1. The Impact of Exercise on Mitochondrial Biogenesis in Skeletal Muscle: A Systematic Review and Meta-Analysis — 2025.
2. Effects of Exercise Training on Mitochondrial and Capillary Growth in Human Skeletal Muscle: A Systematic Review and Meta-Regression.
3. Mitochondrial Dysfunction in Age-Related Metabolic Disorders.
4. Sleep Deprivation and Mitochondrial Function: A Review of the Literature.