New Scientist | connecting-the-dots

[I] A fresh understanding of how the brain assesses bodily energy levels is revealing ways to regain your inner vitality - Caroline Williams

Feeling tired all the time is one of the most common reasons to seek medical attention.
Professionals commonly abbreviate it to TATT (Tired All The Time)

How we perceive this state largely hinges on the brain's ongoing assessment of how much energy is available to our cells.
The energy we can feel - our subjective vitality. It isn't a simple readout on a tank of fuel.

It is an ongoing body - brain estimate of how much energy is available in the body and how much is already accounted for and an educated guess of whether we have any spare for what we need to do next.
This feeling is an example of interoception, the ability to sense signals from within body that tell us how well we are adapting to the world.
The study of interoception is revealing that our feelings, emotions, and motivations are built from an ongoing, constantly changing conversation between body and brain.
It is about figuring out where in the body - brain conversation the signal to conserve energy is coming from, and taking action to fix the issue.
It might be a problem with energy release in the cells, or that the brain is expecting a physical or mental challenge and wants to keep something in reserve just in case. Or it could be something, such as stress or a fight against infection, you feel lousy.

The western approach to medicine has done wonders for human life expectancy, increasing it by three decades in less than a century. But it has been less successful at extending the number of years we live in good health. out so called health-span.
[!] From 2021, globally we are living in an average of 9 years beyond this, in poorer health.

It is time to change the focus of medical research away from treating disease and towards a better understanding of health.
Required a better understanding of how energy flows through the body.

When mitochondria aren't working efficiently, people feel lethargic and fatigued.
Explore what energy release in mitochondria has to do with how energetic we feel and vice versa. Biggest drain on energy production in mitochondria is surprisingly a surfeit of fuel.
Energy is released in the mitochondria is gradual, that can't be rushed and have to happen in a certain order.
If too much fuel arrives at once, the mitochondria have to take a break from releasing energy so that the cells can concentrate on storing the excess for later. This leaves us with less energy, not more - at least in the short term.
High sugar diets , lead to inefficient mitochondria and people feel moody and sluggish rather than energised.

Stress, increases the rate at which cells burn through energy by 60%. This is partly, because mitochondria also produce cortisol, a stress hormone that sends out signal that energy is needed to meet a coming challenge.

Lisa Feldman Barrett, a neuroscientist at Northwestern University in Massachusetts, coined the term , "Body budgeting" - it describes the brain's role in managing the energy supplies in the interests of our survival.
She describes body budgeting in terms of predictive processing. That is, the brain works by generating a best guess about what is happening in the wider world, adjusting as necessary based on incoming sensory information.
When the prediction and evidence does not match, the resulting error signal is experienced as a feeling, whether good or bad or full of energy or in need of a nap.

Brain's assessment of our metabolic state could explain why it is perfectly possible to sleep well and still feel exhausted at the thought of a long day of meetings ahead.
Unexpected piece of good news can translate into a instant energy boost.
Brain's prediction of what there is to work with has transformed the situation.

When people asked to exercise to exhaustion, those who did so in the company of a supportive friend, were able to keep going for a longer and to burn more calories before giving up.
We can dig deeper into our energy reserves when we are confident that help is at hand. Social support signals availability of the resources we need to recover from the exercise so we can be less cautious with our bodily resources.
People, you surround yourself with affect your energy levels in a very real sense.
That our body and brain are wired so that, in the right company there is usually enough energy to go around.

There are several candidate bio markers, that reflect physiological processes and the subjective feeling of vitality or fatigue.
One is growth differentiation factor 15 (GDF 15), a metabolic signalling molecule that cells release when under stress. This occurs in response to infections, injury and psychosocial stress. This is to inform the brain that it needs to conserve energy.
This also explains why getting older only ever seems to make us more tired. It is a reliable marker of ageing with levels in the blood rising by upto 25% as each decade passes. The symptoms of ageing, including fatigue are due to cells accumulating damage and struggling to keep up with the energy costs of repairs. As the debris piles up, the cells send distress signals to the brain, which responds by conserving energy wherever possible.

In 2021, the WHO convened a group to thrash out a new definition of health based not on the absence of disease, but on what they call vitality capacity, the body's ability to extract enough energy from food to stay in good working order.

Stressful periods, in these people's lives could be linked with periods of greying. Then, once stress passed, the colour returns.
The body - brain system temporarily diverts the energy it would normally spend on hair pigment to something more important.
It does suggest that the rate of ageing maybe more malleable than we think.

To understand the chronic fatigue syndrome (CFS) also known as myalgic encephalomyelitis (ME) in which the symptoms are notoriously difficult to explain.
Linked to CFS to reduced blood flow that robs the mitochondria of fuel, with chronic inflammation that saps the body's reserves and with a processing bottleneck in the brain stem, an interoceptive processing hub that has a hand in energy budgeting.

"DEEP REST"

Contemplative practices such as meditation, and prayer, have been shown to enhance well being that they calm the body and mind, reducing the perceived need to hunker down and save energy.

Diet and exercise also play an important role in our energy budgeting. Sugary snacks have been shown to crash mood and energy levels.
Short periods of activity or exercise forces the body to increase the energy production by clearing out inefficient mitochondria and replacing them with fresh ones, that work better.