"Foods Designed to Hijack Our Appetites"
The importance of satiety is underscored by a rare genetic condition
known as Prader-Willi syndrome. Children with the disorder are born
with impaired signaling between their digestive system and their brain,
so they don't know when they're full. With no sensation of satiety,
they can accidentally eat so much they fatally rupture their stomach.
Without satiety, food can be a death sentence.
Protein is often described as the most satiating macronutrient.
People tend to report feeling fuller after eating a protein-rich meal,
compared to a carbohydrate- or fat-rich one.
The question is: does that feeling of fullness last?
From a weight loss standpoint, satiety ratings only matter
if they end up cutting down on subsequent calorie intake,
and even a review funded by the meat, dairy, and egg industries acknowledged
that this does not seem to be the case for protein.
Hours later, the protein consumed earlier
doesn't tend to end up cutting calories later on.
Fiber-rich foods, on the other hand, can suppress appetite and
reduce subsequent meal intake more than 10 hours later, the next day,
because its site of action is 20 feet down in the lower intestine.
Remember the "ileal brake" from my Evidence-Based Weight Loss lecture?
Secretly infuse nutrients into the end of the small intestine and people
spontaneously eat as many as hundreds of fewer calories at a meal.
Our brain gets the signal that we're full from head to tail.
Remember, we were built for gluttony. It's a hedge against times of scarcity.
Stumbling across a rare bounty, those who could stuff themselves the most
to build up the greatest reserves would be more likely to pass along their genes.
So we are hard-wired not just to eat until our stomach is full,
but until our entire digestive tract is occupied.
Only when our brain senses food all the way down at the end
does our appetite fully dial down.
Fiber-depleted foods get rapidly absorbed early on, though,
so much of it never makes it down to the lower gut.
So, if we're eating low fiber, no wonder we're constantly hungry and
overeating; our brain keeps waiting for the food that never arrives.
That's why even people who have stomach stapling surgeries,
leaving them with a tiny two-tablespoon sized stomach pouch,
can still eat enough to regain most of the weight they initially lost.
Without sufficient fiber transporting nutrients all the way down
our digestive tract, we may never be fully satiated. As I described
in my last video, one of the most successful experimental
weight loss interventions ever reported
in the medical literature involved no fiber at all though.
What was going on with that? At first glance it might seem
like a no-brainer that removing the pleasurable aspects of eating
would cause people to eat less, but remember, that's not what happened.
The lean subjects continued to eat the same amount,
taking in thousands of calories a day of the bland goop.
Only those who were obese dropped from eating thousands
of calories a day down to hundreds. This happened inadvertently
without them apparently even feeling a difference.
Only after eating was disconnected from the reward
was the body able to start rapidly reining in the weight.
See, we appear to have two separate appetite control systems:
the homeostatic system and the hedonic system.
The homeostatic pathway maintains our calorie balance
by making us hungry when energy reserves are low
and abolishes our appetite when energy reserves are high.
In contrast, our hedonic or reward- based regulation can overwhelm
our homeostatic pathway in the face of highly palatable foods.
This makes total sense from an evolutionary standpoint.
In the rare situations in our ancestral history when we'd stumble across
some calorie-dense food, like a cache of unguarded honey,
it would make sense for our hedonic drive to jump into the driver's seat
to gobble up the scarce commodity. Even if we didn't need the extra calories
at the time, our bodies wouldn't want us to pass up that rare opportunity.
Such opportunities aren't so rare anymore, though.
With sugary, fatty foods around every corner, our hedonic drive may end up
in perpetual control, overwhelming the intuitive wisdom of our bodies.
So, what's the answer? Never eat really good-tasting food?
No, but it may help to recognize the effects hyperpalatable foods can have
on hijacking our appetites and undermining our body's better judgment.
Ironically, some researchers have suggested a counterbalancing
evolutionary strategy for combatting the lure of artificially
concentrated calories. Just as pleasure can overrule
our appetite regulation, so can pain. Conditioned food aversions
are when we avoid foods that made us sick in the past.
That may just seem like common sense, but it's actually a deep-seated
evolutionary drive that can defy rationality. Even if we know for a fact
a particular food was not the cause of an episode of nausea and vomiting,
our body can inextricably tie the two together.
This happens, for example, with cancer patients undergoing chemotherapy.
Consoling themselves with a favorite treat before treatment
can lead to an aversion to their favorite food
if their body tries to connect the dots. That's why oncologists may advise
the scapegoat strategy of only eating foods before treatment
you're okay with never wanting to eat again.
Researchers have experimented with inducing food aversions
by having people taste something before spinning them in a rotating
chair to cause motion sickness. Eureka! A group of psychologists
suggested this kind of strategy as a way of encouraging people to eat less
unhealthy food: make them sick of the food by making them sick from the food.
Or hey, what about using disgust to promote healthier eating?
Children as young as two-and-a-half years old will throw out
a piece of previously preferred candy, scooped out of a brand new,
sparkling clean toilet bowl. Thankfully, there's a way to exploit your instinctual
drives without resorting to revulsion, aversion, or bland food,
which we'll explore next.