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Some of us may simply
have been born with a At a cellular level, scientists are increasingly
looking at the role of mitochondria – the power
physical and psychological packs in every human cell – in determining
how tired we feel. Mitochondria are miniature
susceptibility to tiredness organs (organelles) that convert oxygen, sugar,
fats and protein into a form of chemical energy,
called ATP, which the body uses to fuel the
5 Until now, little has been known about the brain and muscles. Diseases affecting the
biological processes that result in what we call mitochondria cause fatigue, so recent reviews of
tiredness or fatigue. Only in recent decades, research suggest that fatigue is closely associated
with growing concern about the prevalence with mitochondria not working properly
of conditions such as CFS/ME, has research because the body is not producing particular
money been invested into the causes of long- enzymes, for example.
term fatigue. As a result it’s becoming clear Studies into CFS/ME by fatigue expert
that, although there is a wide spectrum of Dr Robert Naviaux have shown that the condition
types of tiredness, they are all linked and their is characterised by changes in mitochondria
causes interact. function. Dr Naviaux believes that these changes
Prof Julia Newton, director of the Newcastle may be triggered by stressors such as infection,
Centre for Fatigue Research at Newcastle or physical and psychological trauma.
University, explains the causes of tiredness Dr Naviaux cites new literature indicating that
via a classic bell-shaped curve graph. “At the stress can prompt metabolic changes, which
thin end of the curve, there are people who just make organisms go into hibernation-like states
need to get some sleep and get their lifestyle such as torpor and aestivation. “Both of these
in order. At the other thin end of the curve is an energy conservation state that permits
there are clearly people who have diagnosed or survival under conditions of environmental
undiagnosed illnesses that are causing fatigue. stress at the expense of a decrease in the ability
And then, there’s everyone else in the wide, to allocate energy for daily work or activity,” he
middle part of curve.” says. “Mitochondria are central control points
The wide middle is the complex bit, covering for each of these processes.”
tiredness caused by combinations of many This initial research about the metabolic
A mitochondrion, a cell’s environmental, lifestyle and health factors. origins of fatigue may link with other studies
‘power pack’, has a highly And recent research is beginning to reveal suggesting that sometimes tiredness has
folded inner membrane
that’s packed with how genetics, cell function, inflammation and underlying but undiscovered physical origins.
substances involved in the the brain’s response to light may all have an For example, recent studies have indicated that
creation of ATP, which the
body uses for energy underlying role in this tiredness ‘mainstream’. severe fatigue is associated with raised levels of
leptin, a hormone produced in fat tissue, which
signals to the brain that the body has adequate
energy stores. This raises the prospect that too
much leptin – possibly from too much body
fat – means we naturally feel less energetic:
if we don’t need food we don’t need to go out
and do something about it. This links with
anecdotal evidence that intermittent fasting
and reducing body fat can improve people’s
energy levels.
It also links with research indicating that
people with CFS/ME can have high levels of
leptin and similar inflammation-producing
substances called cytokines. Cytokines, which
are also produced in fat, are released during
76 BBC SCIENCE FOCUS MAGAZINE COLLECTION
