Metabolic reset: mitochondria, energy and healthy ageing

Mitochondria are structures within cells that produce much of their ATP. This molecule serves as an immediate energy carrier for many cellular processes. Mitochondria are therefore often described as tiny power stations. They do not create energy from nothing: they convert energy from nutrients into a form that cells can use. [1]

Tissues with high energy demands, such as muscle, need many mitochondria. However, this does not mean that every feeling of tiredness indicates mitochondrial dysfunction or a shortage of ATP. How energetic you feel is not a measurement of mitochondrial function.

Carbohydrates are not limited to sweets. Fruit, vegetables, pulses and wholegrain foods also contain them. WHO recommends prioritising these sources. For most people, paying attention to food quality is more useful than setting aside a compulsory day without any carbohydrates. [2]

• Replace sugary drinks with water or unsweetened drinks more often.
• Include a variety of vegetables, pulses and other fibre-containing foods.
• Include a protein source in main meals, such as fish, eggs, yoghurt, tofu or pulses.
• Complement your diet with appropriate amounts of nuts, seeds and plant oils.

Berries, tea and olive oil can all form part of a varied diet. There is no need to attribute the ability to “repair mitochondria” to a single food. Your overall eating pattern matters. [2, 3]

The body changes the proportion of energy sources it uses according to nutrient availability and its needs. During a longer period without food, its use of stored energy changes; with longer fasting, ketone production also increases. These metabolic changes alone do not demonstrate rejuvenation or a longer lifespan. [4]

Intermittent fasting covers several eating patterns. Some restrict eating to certain hours of the day; others limit energy intake on selected days. For some people, fasting can be a way to reduce overall energy intake and body weight. However, it is not automatically more effective than another sustainable eating pattern. [5]

We do not recommend a full-day fast every Sunday as a general rule. Being able to tolerate hunger does not establish whether fasting is suitable for an individual. A carbohydrate-free day is not equivalent to fasting either.

Autophagy is the breakdown and reuse of cellular components. Mitophagy is a selective form of this process that targets mitochondria. It is part of cellular quality control, rather than a simple switch that turns on after the same number of hours without food in everyone. [7]

Researchers are studying how different eating patterns affect autophagy in humans. Findings from small studies cannot be translated into a promise that a particular fasting duration will rejuvenate the whole body. For example, a recent pilot study measured changes in certain blood cells; its authors highlight the need for larger studies. [8]

Our separate Slovak-language article explains these processes in more detail, including the complex role of autophagy in cancer.

Regular physical activity has well-documented health benefits. WHO recommends that adults aim for 150–300 minutes of moderate-intensity aerobic activity per week, or an equivalent amount of more vigorous activity. This should also include muscle-strengthening activities involving the major muscle groups on at least two days a week. [9]

If you have not been very active, start with shorter sessions and gradually adapt the workload to your fitness. A walk, getting up more often during sedentary work, and simple exercises with appropriate resistance can be practical starting points.

The aim is not exhaustion. Choose activities you can repeat regularly and that respect any health limitations.

Adults are generally advised to get 7–9 hours of sleep per night. Sleep needs can vary between individuals and circumstances. Sleep should therefore not be limited to whatever time remains after every other task is done. [10]

Try to allow enough time for sleep, keep a reasonably consistent wake-up time and make the end of the day calmer. A short break, a walk or some time away from work-related demands can be a simple part of your routine.

If you remain noticeably tired over a long period despite allowing enough time for sleep, do not automatically attribute it to age or mitochondria. It is worth discussing the cause with a healthcare professional.

Photobiomodulation research investigates the biological effects of light, often in the red and near-infrared ranges. Effects on mitochondrial activity and ATP are among the mechanisms being studied. However, outcomes depend on the conditions: wavelength, intensity, dose and target tissue. [11]

Ten minutes is not a universal dose. The same exposure time with different devices may deliver different amounts of energy. A higher dose does not necessarily produce a greater effect.

A change in ATP in a laboratory experiment does not establish that a person will feel more energetic or age more slowly. We therefore present light as a research topic, rather than a proven method of achieving a metabolic reset. Any specific device must be used according to its intended purpose and instructions.

No. Fasting is not a requirement. It is one of the eating patterns under investigation and may not suit everyone. This article focuses on sustainable habits, rather than compulsory fasting. [4, 5]

No. Ketosis describes a metabolic state. It is not, by itself, evidence of rejuvenation or a direct measurement of autophagy. [4, 7]

Your subjective sense of energy is not a direct measurement of ATP. How you feel cannot determine ATP levels in individual tissues or diagnose the condition of your mitochondria.

No. This article does not describe a clinically validated combined programme for slowing ageing. It explains general recommendations and separately identified research topics.