WHEN
YOU EAT IS (ALMOST) AS IMPORTANT AS WHAT YOU EAT
Prof.
David Cameron-Smith
Before
you surrender to that late night craving for leftovers or a post-party burger,
spare a thought for your body’s natural rhythms and what messing with them does
to your health and wellbeing.
The first rays of morning sun
begin an ancient cycle that connects every living thing. All animals have a
24-hour biological clock, known as a circadian rhythm, that has a powerful
influence on physical activity, alertness, mood, hunger and metabolism.
And when this biological clock
meets a modern 24/7 lifestyle, the human animal can suffer.
The phases of the sun trigger our
sleep and wake cycle. Upon waking, a small
cluster of nerves located deep in the brain, called the Suprachiasmatic Nucleus (SCN),
come into play. These several thousands of nerves are located within the hypothalamus,
the region of the brain that regulates many brain pathways, including those
that determine when you want to eat, as well as how much and what type of food.
The SCN functions by sending out
signals, firstly through the hypothalamus, then on to every other part of your
body. Within each and every one of the billions of cells that make up the human
body, the SCN controls the activity of a cluster of so-called CLOCK genes
(technically, “Circadian
Locomotor Output Cycles Kaput” – try saying that with a mouthful of cheesecake).
Named for their daily switching
on and off, the CLOCK genes are master regulators of whether cells are more or
less active. During the night, CLOCK genes turn down the metabolic processes of
many cells. During the day, the reverse
is true and cells are revved up and maximally active.
Messing
with the natural sleep cycle
Just one late night or a period
of disrupted sleep can unravel the synchronization of the SCN and CLOCK genes.
Apart from the tiredness, there are the more subtle signs of metabolism gone haywire
– blood pressure is increased, circulated levels of stress hormones rise,
levels of bad fat (LDL cholesterol) are raised, and bowel habits begin to
change. Inconvenient, yes, but not particularly detrimental to health.
However, multiply this to being
chronically sleep deprived, jet-setting through multiple time-zones or
switching work shifts, and the disturbances become more hazardous. For the
estimated 20 percent of the working population who work irregular hours –
either on rotating shifts, irregular schedules or night work – the health
effects need to be considered.
Sleep
loss and weight gain
Disconnected circadian rhythms
and eating times alter the biological responses to food. During the day, the
digestive tract, pancreas and metabolic tissues are primed and ready for
nutrients. After eating, food is readily digested, insulin is produced and
nutrients are rapidly stored and metabolised.
The exact same meal eaten out of
synch results in a delayed insulin response, slowed storage, and disturbed
metabolism. Because the body is not expecting to metabolise the food, it is stored.
The exact same meal eaten at the wrong time is more likely to result in weight
gain.
Sleep
it off!
Then there are appetite hormones.
Eating out of synch can be a disaster for what – and how much – you choose to
eat. Late night snacks and meals tend to be higher in calories and are more
likely to be convenience snacks or purchased foods. You are far less likely to
be eating a piece of fruit at 2am than raiding the fridge or eating a greasy
kebab. Part of the reason for this can be traced back to the hormones that are
controlled by your SCN.
So the timing of when you can be
the secret to helping you shed those few unwanted extra pounds. There is good
scientific evidence that a late lunch and dinner make it harder to lose weight.
In a published scientific study, night owls lost less weight in a carefully
controlled weight loss intervention than those on normal circadian cycles.
The take out from this – aside
from going easy on the take out? Try as much as possible to keep to a regular
pattern of eating and sleeping.
