Translator: Mirjana Čutura Reviewer: Rhonda Jacobs
So, as a neuroscientist,
I'm fascinated by how our brains control our behaviors
in our dynamic and changing world.
But recently,
I've become really interested not only in the environment that we live in,
but what we're putting into our environments, our bodies,
in the form of the food that we eat.
Now,
we all eat junk food.
I'm not going to lie - I've eaten pizza twice this week.
But we know it's bad for us, yet we continue to eat it.
It's so tasty, and it's everywhere, and it's really hard to resist.
So, one of the things I've been really interested in
is how this not only is affecting our bodies -
now that a quarter of all young Australians are overweight or obese -
but also what it's doing to our brains.
These foods are so hard to resist
because they're rewarding, they taste so good.
And when we consume these foods,
our brain's reward center activates, and it releases the chemical dopamine.
Dopamine makes us feel good, and we really like it.
So actually, when we overconsume these foods,
our brains become overwhelmed
with the pleasurable experiences that we're having.
So, our brain's pretty clever,
and it adapts.
It creates more receptors for dopamine.
And what happens then is that we need more of these foods
to get the same kick out of them.
Our brain is basically hardwired to seek and want these foods,
but we're building up a tolerance to them,
so we eat more.
So we're basically becoming sugar junkies.
Dopamine is really cool as well.
It does things that make you learn about how good these things are.
Because we really like them, it directs our attention to them,
so we see them when we're there getting our coffee in the morning,
feeling a little bit shabby.
We see the doughnut, and we can't resist it.
We're like, "Yeah, that's a healthy breakfast."
(Laughter)
And we just can't resist these things.
But we need a part of the brain that controls our urges and temptations
because, otherwise, we'd just be, you know, eating doughnuts
for every meal of the day.
The brain has an area called the prefrontal cortex.
This area is responsible for your cognitive control.
It controls your behaviors in the world.
It's also the last part of your brain to mature,
and it doesn't actually fully mature until you're in your 20s.
And this means that when we think about all these people
who are developing obesity because of their environment,
they're finding it really hard to resist these temptations at a young age
because their brain isn't yet fully functioning.
So, I actually do my research with rats, not people.
And they really like junk food as much as people do.
(Laughter)
What's great about rats is that they have the same areas of the brain as humans,
and they have the same neurochemistry,
so we can use them to study how their diet impacts on their behavior
without, you know, having to deal with people.
So, in my lab,
we've been thinking about how adolescence is a particularly vulnerable period
for the development of cognitive deficits caused by the consumption of these foods.
So, I've been feeding teenage rats -
so, rats go through adolescence and puberty as well -
with this highly sugary solution,
which is about the same, really, as a can of Coca-Cola
in terms of the amount of sugar,
all through their adolescence.
And then I test them on tasks that require them to use their brains,
use cognitive control, make decisions, and follow rules.
What I've found is that rats that are fed these sugary solutions
aren't able to follow the rules as well as healthily diet-fed rats.
When we ask them to press a lever according to a certain signal -
be it an auditory or visual cue -
what actually happens
is they show impairments at this sort of rule-following.
And we think about our population now developing more and more obesity,
it's not surprising that, in the face of "don't eat the doughnut,"
that these people are overeating causing them to develop obesity.
But these diets don't just affect our behavioral control,
they affect the area of the brain that's responsible for memory.
This is the hippocampus.
Now, when you consume these foods, your body has a response to them.
And if your diet is really consistently full of them,
you develop a form of inflammation, but in your brain.
So this is called neuroinflammation -
so neuroscientists, we put "neuro" in front of things -
and it's kind of like getting hives
when you consume something that you're allergic to.
And this is happening in the memory center of your brain,
so it's actually impairing your ability to learn and remember facts
because the inflammation is causing the neurons,
the brain cells in your brain, to malfunction.
This means that people who consume lots and lots of junk foods
don't perform as well on memory tests as those who eat healthy diets.
And this research actually showed
that these people didn't actually have obesity -
they were the same weight
as the control people who eat healthy diets.
Research has also shown that people with damage to the hippocampus -
so, the memory center -
report feeling hungry all the time.
When I read about this research,
I thought maybe they just don't remember eating.
(Laughter)
But actually,
the hippocampus is a critical area of the brain
for receiving fullness signals from the gut.
So we're setting up another vicious cycle
where, if you're consuming a lot of these foods,
you're developing obesity - overconsuming -
because you're not getting the same fullness signals from the gut.
So you're eating more junk food, which is, in turn, damaging your brain.
This means that your brain can be reduced in terms of its neuroplasticity,
which is how these neurons are firing together and wiring together
to form your memories.
But also, these neurons are born in your brain throughout life,
particularly in the hippocampus.
This is called neurogenesis, and it occurs throughout your life.
These new neurons are particularly plastic.
They form memories readily, and they're really important.
We know that people who consume high-fat diets -
from research with rodents -
have got lower amounts of neurogenesis.
But people with mental health disorders,
such as depression,
also have lower levels of neurogenesis,
which again brings about another idea of a vicious cycle.
We know that these foods are really tasty.
They release dopamine; dopamine makes us feel good.
So if we comfort-eat these foods,
we're actually then diminishing our neurogenesis,
which is actually making us sadder in the long run.
So that's kind of a depressing point.
I'm really sorry.
But it's really important for us to be mindful
of what we're putting into our bodies
and how it's affecting both our body and our brains.
And for young people, it's especially important
because this is such a critical period in your life
for learning about the world and learning new things and concepts.
So when you're stressed out, you can think,
"Oh, I just want to comfort-eat and just consume pizza and doughnuts
and then revise for my exam tomorrow morning."
But this isn't going to be ideal
for your brain to remember all these facts.
But research provides us with these methods
that the brain is being affected by in terms of these diets.
And so it provides us with ways that we can counteract these effects.
I'm sorry, but you can eat healthy foods.
I mean, fruit and veg are really good for you.
They contain antioxidants.
And these fight inflammation and neuroinflammation.
If you eat avocados and oily fish,
these contain a lot of omega-3s, and these are able to boost neurogenesis.
And by being active in your lifestyle, getting out and running around,
it doesn't just help you lose weight by burning off excess calories,
but it also boosts neuroplasticity mechanisms in the brain.
So, I'm not going to tell you to never eat junk food ever again.
We all do it.
But we need to treat these foods
in the same way that our brain treats these foods -
as a reward,
as opposed to the major part of our diets.
(Applause)