Yeah, been to KK, was thinking of going to Borneo soon, but the
air prices made me do a double-take.
****
For the resident big-eaters:
Waistband feeling a bit tighter, or buttons straining after
Christmas?
While it’s easy to blame your appalling willpower or
TV-inspired lethargy, according to a respected U.S. obesity expert,
weight gain might not be your fault at all.
In a fascinating new book, Robert Lustig, a professor of
clinical paediatrics at the University of California, expounds a
whole new scientific theory.
He argues that the urge to overeat and lounge around doing
nothing is not a sign of weakness.
It is, he says, a hormonal issue, triggered by eating too
much sugar.
He points the finger of blame at the hormone leptin, which
acts like an appetite thermostat.
As one of two ‘hunger hormones’ in the body, leptin works to
decrease the appetite (its partner, ghrelin, increases
appetite).
When you have had enough to eat, your fat cells release
leptin, which effectively dulls the appetite by instructing the
brain that it’s time to stop eating.
But Professor Lustig warns that our sweet tooth is sending
this process haywire.
For many years scientists thought obesity could be caused by
a shortage of leptin — thinking that without adequate levels,
overweight people simply never received the message that they were
full.
But more recent studies have shown that obese people have
plenty of leptin (in fact, the fatter you are, the more of it you
appear to have), but are more likely to be
‘leptin-resistant’.
This means the cells in the brain that should register leptin
no longer ‘read’ the signals saying the body is full, but instead
assume it is starving — no matter how much food you continue to
eat.
In panic, the brain pumps out instructions to increase energy
storage — instigating powerful cravings for high-fat, high-sugar
foods because these are the easiest and most immediate forms of
energy — and conserve energy usage, by dampening any urge to get up
off the sofa and go for a run.
The food cravings are made even more intense — and impossible
to resist — because leptin is supposed to dampen the feeling of
pleasure and enjoyment you get from food by suppressing the release
of the brain chemical dopamine, helping to decrease
appetite.
But if you are leptin-resistant, food never stops tasting
delicious, no matter how much of it you eat.
This, says Professor Lustig, is why many overweight people
find it so hard to stop eating, and why diets so often
fail.
Scientists have been struggling to work out what causes
leptin resistance.
But now Professor Lustig and his team have been able to show
— in repeated studies on humans — that too much sugar in the diet
is to blame.
High sugar diets lead to spikes in the
hormone.
This is needed to clear sugar out of the blood and into
storage as fat.
But repeated insulin spikes, due to a high sugar diet, can
lead to a condition called ‘insulin resistance’ (when the cells
have been so bombarded by insulin they no longer respond to
it).
Professor Lustig believes insulin resistance triggers leptin
resistance, and, crucially, he has discovered that by reducing
insulin levels it is possible to improve ‘leptin signalling’ (the
brain’s ability to read leptin), stop cravings, put the brakes on
food consumption — and trigger weight loss.
In his new book Fat Chance, Professor Lustig explains that
leptin resistance — and sugar — is at the root of the obesity
epidemic.
A high sugar diet can trigger leptin resistance even if
you are just slightly overweight. This is because sugar triggers a
spike in insulin
He believes 1.5 billion overweight or obese people in the
world suffer from this condition — and is convinced that the
problem can be tackled by targeting insulin.
In his studies, many participants took insulin-lowering
drugs, but the professor says similar results can be achieved by a
few small lifestyle changes — notably reducing sugar in your
diet.
The professor has a heavyweight background in endocrinology
(the study of hormones), as both a medical doctor and
academic.
He used organised trials to study the role the brain
plays in governing appetite and activity levels and found that
patients who had damage to the hypothalamus (the area of the brain
that controls energy levels) could not lose weight, but somehow
gained weight even when restricted to a near-starving 500 calories
a day.
Lustig realised that a similar process could be happening
with obese adults and set out to investigate a potential
solution.
His studies revealed that the roles of leptin and insulin are
intertwined, and bind to cells in the same area of the brain — the
hypothalamus.
A high sugar diet can trigger leptin resistance even if you
are just slightly overweight. This is because sugar triggers a
spike in insulin.
While leptin activates biochemical reactions that send
‘satiety signals’ to the brain, insulin can very effectively block
these signals, resulting in no satiety, no sense of fullness, and
uncontrolled eating of high fat, high sugar
foods.
This is leptin resistance, and leaves the brain ‘blind’ to
leptin signals, so it still thinks we’re
hungry.
Even worse, in healthy people, one of the things leptin
should do is to tell the brain to reduce insulin production. It
does this by dulling appetite and thus reducing food intake (so
cutting the body’s need to produce yet more insulin to deal with
the food).
But if you have too much insulin and you are leptin-resistant
this doesn’t happen, and insulin levels rise ever higher, creating
a vicious cycle.
Lustig believes that our high sugar diets cause continually
stimulated insulin production.
He says the insidious creep of insulin resistance means that
our bodies now produce double the insulin for every teaspoon of
sugar consumed compared to 30 years ago.
He says insulin resistance is now so widespread, it affects
the majority of overweight people and even as many as 40 per cent
of those who are normal weight (if they eat too much sugar and
refined carbohydrates like white flour, bread, pasta and
rice).
And leptin resistance becomes more of a problem with
increasing body size: ‘Plump people might have a little leptin
resistance, but the morbidly obese will have a lot,’ he
says.
Professor Lustig believes that our high sugar diets cause
continually stimulated insulin production
The sweet, processed food that makes up so much of the modern
diet (much of it disguised as ‘low fat’ and therefore healthy) has
addictive qualities — particularly for those caught up with leptin
resistance.
When we eat food, the brain chemical dopamine is released,
creating a feeling of pleasure and reward, explains Professor
Lustig.
Then leptin kicks in to suppress the release of dopamine, so
that we get less reward, and therefore we stop
eating.
But, he adds, if you’re leptin-resistant, the dopamine won’t
be suppressed properly, and it remains at high levels in the brain,
and ‘floods’ the brain cells.
After many meals (over a period of about three weeks) brain
cells may start to become ‘tolerant’ to these persistently high
levels of dopamine.
They build up resistance, meaning that higher and higher
amounts of dopamine are needed to trigger a reward
signal.
As a result, you may feel compelled to eat greater quantities
to achieve the same sense of satisfaction. This can swiftly turn
into sugar addiction.
Insulin also works to clear dopamine from the brain,
gradually blunting the reward felt for further
food.
But if you’re insulin-resistant too, the brakes won’t work,
and the reward impetus continues unabated.
This, Professor Lustig believes, explains why many people can
want, and apparently enjoy, never-ending quantities of food even
when energy stores were long ago full — for example over the
Christmas period.
He fears insulin resistance (and therefore leptin resistance)
may also start in the womb, and that exposure to high sugar diets —
via the mother — may trigger genetic changes that increase a baby’s
risk of insulin and leptin resistance in later
life.
But he adds: ‘At the end of the day, it is what you eat (and
of course, how much of it) that puts the final nail in the
coffin.’
Conventional wisdom and government policy still blame dietary
fat for our ever-rising obesity levels (and horrific heart disease
statistics).
However, Professor Lustig is part of the band of obesity
specialists who question the validity of the hugely influential
research conducted in the Fifties, which identified dietary fat as
the trigger for weight gain and heart disease.
The seminal ‘Seven Countries’ study by U.S. epidemiologist
Ancel Keys in the Eighties demonised fat, triggering a massive
change in food manufacture.
In an effort to make low fat food more palatable, many
manufacturers raised the carbohydrate level, adding quantities of
sugar to almost everything (both sweet and
savoury).
For instance, a small pot of low fat yoghurt can contain as
much as four teaspoons of sugar, and even wholemeal bread hides two
teaspoons per loaf.
Gradually tastes and eating habits have changed, Lustig says,
resulting in growing populations worldwide inadvertently hooked on
easy-to-eat high sugar foods.
As he puts it: ‘The obesity epidemic was born in the
aftermath of this seemingly logical and well-meaning, yet
tragically flawed understanding of our
biochemistry.’
Mercifully, it is not all doom and gloom.
‘Obesity is a hormonal problem and hormones are alterable,’
says Professor Lustig.
He recommends simple steps, detailed below, that can lower
your leptin levels.
These include reducing sugar in every recipe by a third,
increasing your fibre intake, and taking just 15 minutes of
activity every day.
Adapted from Fat Chance: The Bitter Truth About Sugar,
by Robert Lustig, published by HarperCollins on January 3 at
£13.99.
© Robert Lustig 2013. To order a copy for £9.99 (postage and
packing free), call 0844 472 4157.
Professor
Lustig believes the key to losing weight is to reverse leptin
resistance. Here is his action plan:
When
cooking, reduce sugar in every recipe by a third, and eat dessert
as a treat, once a week.
Fibre is now
routinely stripped from foods to give a finer texture and extend
shelf life (manufacturers have found food with fibre doesn’t freeze
well, and can’t be cooked quickly), but according to Professor
Lustig: ‘Fibre, or roughage, is the most misunderstood weapon in
our nutritional arsenal.’
This is
because the digestive system has to work to strip away the outside
bran of a wholegrain, so slowing the whole digestive process, and
stopping glucose levels from peaking suddenly.
This means
less insulin is released, therefore less energy is stored as fat.
Slower digestion also gives your brain a chance to register that
you are full.
Exercise
alone cannot cause significant weight loss (unless you change your
diet at the same time) but Professor Lustig says 15 minutes a day
is enough to improve your insulin sensitivity (because activity
helps cells become more receptive to insulin), and build muscle at
the expense of fat.
Although you
may not see a drop on the scales, by improving insulin sensitivity
and lowering insulin levels, exercise, will improve leptin
signalling.
Beware
packaged food. Professor Lustig’s mantra is: ‘Don’t eat anything
your grandmother wouldn’t recognise. If the food has a company logo
you’ve heard of, it’s processed.’
Eating
standing up means you will be eating fast, with no time for satiety
signals to kick in, says Professor Lustig.
Always
include some sort of protein (chicken, pulses) in every meal (to
slow the digestive process and reduce the risk of insulin spikes)
and avoid any ‘food’ that is just fat, carbohydrate and sugar (such
as doughnuts, milk-shakes, pastries).
