Article copied from ABC website
Our obsession with fats and carbs means we're looking at
nutrition all wrong.
"Eating pasta helps you lose weight." "Eating
more animal protein increases risk of death." "The foods helping you
shred stomach fat." "How to eat carbs without gaining weight."
These are all real headlines, published in separate media
articles recently.
Is it any wonder that people are confused about what they
should and shouldn't eat?
Daily we hear of another nutritional dietary
"breakthrough". But as a cursory look at Australia's obesity
statistics attests (two in three Australians are obese or overweight), our
health and wellbeing are reaping no benefit.
What's worse, fats or carbs?
So what's gone wrong? Why are clear, useful and effective
messages about nutrition so difficult to find?
The answer is that we have taken a wrong turn in the way
that we think about nutrition. We are too obsessed with identifying an
individual culprit — a specific nutrient that causes a particular health
problem.
Take for example the argument whether fats or carbs causes
obesity. It began over half a century ago, and yet the debate remains
unresolved.
Some experts argue that fats are to blame, others that carbs
(especially sugar) are almost solely to blame, and to further complicate
things, yet others suggest too much protein or too little fibre as the cause.
None of these viewpoints is entirely incorrect, but in
reality, obesity is not caused by a single nutrient.
Rather, like a high-functioning sports team, particular
nutrients interact in networks of other nutrients to influence energy intake
and fat storage.
To solve the problem we need to reconsider the question we
ask. Rather than "which nutrient causes obesity?” we should ask
"which combinations of nutrients are associated with obesity?"
Nutrition is about mixtures, not single nutrients, and their
actions can be indirect and unexpected.
We had bad dietary advice in the '70s
Not only has the single-nutrient approach failed to manage
the obesity crisis, it might actually have contributed to it. In the 1960s and
1970s, when obesity first emerged as a serious health problem, dietary fat took
too much of the rap.
Official advice was, quite logically, to reduce the amounts
of fat in the diet. And we did — the public health messages worked, but it had
no effect. By the 1980s it was clear there was no sign of the obesity epidemic
slowing, let alone reversing.
People followed the dietary advice, but it was bad advice.
It failed not because fats aren't associated with obesity — they probably are —
but because the focus on a single nutrient had unintended consequences.
Rather than reduce the total amount of energy eaten, which
very likely would reduce obesity, people simply replaced fat in their diet with
carbs.
This was also helped, in no small measure, by the processed
foods industries. Sensing an opportunity, they quickly offered foods
conspicuously labelled "low-fat". What the labels didn't say is that
these foods were also "high-carb".
So if fat isn't responsible, and obesity has continued to
rise with increased carb intake, then surely carbs must be to blame.
Excessive carb intake almost certainly has played a role in
the obesity epidemic (probably together with fat), but there are again
suggestions that singling them out as "the cause" is leading to
problems.
It is causing many to turn to a low-carb diet — for example
the paleo, Atkins and Banting diets. But recalling the fat-carb debacle, if
carbs are reduced then it is likely that something else will replace them. That
something turns out to be protein.
Although low-carb/high-protein diets likely do lead to
reduced energy intake, the evidence is growing that they also have nasty
side-effects. They alter the balance of microbes in the gut, accelerate the
onset of age-related diseases such as cancers, and shorten lifespan.
Demonising fats, carbs, salt, or zangamide (we just made
that up), and implying that reducing their intake alone will solve the problem
of obesity, is simply wrong. That's because attempting to solve health problems
nutrient-by-nutrient is like herding cats. As soon as one nutrient is under
control, another slips out of line.
Enter nutritional geometry
A method is needed to understand nutrition for what it is —
the association between our biology and "teams" of nutrients that
interact to influence our health.
We propose a new approach to nutrition, called nutritional
geometry, which does just this.
Nutritional geometry offers a new tool to model diets as
mixtures of nutrients, foods, meals and menus, and in this way helps
researchers and health professionals to understand how the dietary balance
influences health. It can also help individuals to manage their diet, by
changing the goal from eating diets "high in this nutrient" or
"low in that", to eating a diet that is balanced in nutrients.
We can now look forward to clearer messages around the
relationships between nutrients, foods, diet and health.
In the meantime, one message is clear. Rather than focus on
which nutrient to leave out of the diet, we need to reduce our consumption of
high energy, nutrient-poor snack and junk foods and beverages. By any
definition, these spell trouble for healthy eating.
This article was co-authored by the University of Sydney's
Leonard P Ullmann Chair in Nutritional Ecology David Raubenheimer and Charles
Perkins Centre academic director Stephen Simpson.
