Liquid Calories: Do Smoothies Lead to Weight Gain?


“Liquid Calories-
Do Smoothies Lead to Weight Gain?” A famous study in 2000 compared the
impact of soda versus jellybeans. They had people add 28 extra spoonfuls
of sugar to their daily diet in the form of
jellybeans or soda pop. Then they measured how many calories
they ate over the rest of the day to see if their bodies would
compensate for all that extra sugar. This is how many calories
the jellybeans group was eating before
the study started, but when eating
handfuls of jellybeans, their bodies registered all
those extra calories so they ended up eating less of
everything else throughout the day. So even adding the
jellybean calories, they were eating pretty much
the same number of calories before and after adding the
jellybeans to their diet. But in the soda group, this is
how much they started eating, and despite all the added calories
from the cans of soda they were drinking every day, they
kept eating about the same amount. So with the soda calories added in,
no wonder they gained weight after a month of
drinking soda. Their body didn’t seem to
recognize the extra calories when they were
in liquid form, so didn’t compensate for them
by reducing their appetite so they’d eat less
the rest of the day. This lack of regulation may
be used to our advantage, the researchers suggest,
if you want to get fat. But what if
you don’t? If we drink a smoothie for
breakfast instead of a solid meal, will your body think
you skipped breakfast and make you so
ravenous at lunch you’d eat more than we normally would
and end up gaining weight? OK, well first, is this solid versus
liquid calorie effect real? Soda and jelly beans don’t just
differ by the physical form— they have different
ingredients. That’s a problem with a lot
of these kinds of studies. They use dissimilar foods. Like this study comparing
liquid to solid breakfasts. They either got fruit juices
and skim milk for breakfast or oatmeal with blueberries
and apples in it. And lo and behold, study subjects
were less hungry after the oatmeal. Duh. That may not be a solid
versus liquid effect— those are completely
different foods. To test for a solid versus
liquid effect you’d have to use the exact same food
in just two different forms. Even this study
was flawed. It purported to show that
eating apples before a meal is so good at filling you up that
you eat fewer calories overall, but that pureed apples
weren’t as effective. But they didn’t just
blend the apples, they baked them for
45 minutes first, which may change how
the body handles it. I had seen all these studies,
but was just not convinced there was a solid
versus liquid effect. And then this study
was published. A solid fruit salad, with raw
apples, apricots and bananas with 3 cups of
water to drink or take 2 cups of that water,
add it to the fruit, make a fruit smoothie and then just
drink that third cup of water. So the identical meal;
one in solid form, one in smoothie form. What happened? People felt significantly less
full after the smoothie. Same amount of foods,
same amount of fiber, but in smoothie form it
just didn’t fill people up as much as eating
fruit au natural. Originally we thought it
was the lack of chewing. The act of chewing itself
may be a satiety signal, an I’ve-eaten-enough signal, and indeed comparing 35 chews per
mouthful to 10 chews per mouthful, if you ask people to eat pasta
until they’re comfortably full, those forced to chew 35 times
per bite ended up eating about a third of a
cup less pasta. So there we have it: we have
the proof of solid vs. liquid effect. We have the mechanism here, and
as so often happens in science just when we have everything
neatly wrapped up in a bow, a paradox arises. In this case the
great soup paradox. Soup, pureed, blended soup,
essentially a hot green smoothie of blended vegetables
is more satiating than the same veggies
in solid form. The same meal in liquid form was
more filling than in solid form. So it can’t be the chewing.
In fact there doesn’t appear to be a solid versus
liquid effect at all, since cold smoothies appear
to be less filling, but hot smoothies appear
to be more filling. So filling that when people have
soup as a first course, they eat so much less
of the main course, that even when you add in
the calories of the soup they eat fewer
calories overall. So how can we explain
this paradox? Maybe pureed fruit is
less filling than solid, but pureed vegetables
are more filling? I guess you could try making
apple soup or something, but who’s going to do that…
Purdue University. To prepare apple soup they mixed
about a cup of apple juice with two cups of
apple sauce, liquefied it in a blender and
heated it up. If you have people eat 3
actual apples instead, they start out
pretty hungry, but within 15 minutes
of apple eating they were hardly
hungry at all. Drinking 3 cups of apple juice
didn’t cut hunger much at all, but what about the soup,
which was pretty much just hot apple juice with
apple sauce mixed in? It cut hunger almost as
much of the whole apples, even more than an hour later,
and even beat out whole apples for decreasing overall
calorie intake for the day. What’s so special
about soup? What does eating soup have in
common with prolonged chewing that differentiates them
from smoothie drinking? Time. It took about twice as long
to chew that many times, and think how long it
takes to eat a bowl of soup compared to drinking
a smoothie? Eating slower reduces
calorie intake. Or maybe we just imagine
the soup to be filling and it’s like a
placebo effect. Feelings like hunger and
fullness are subjective. People tend to report hunger
more in accordance with how many calories they
think something has rather than the actual
caloric content. If you study people with
no short-term memory, like in that movie, Memento,
where they don’t remember what happened more
than a minute ago, they can overdose on food, because
they forgot they just ate, which shows what poor judges
we are of our own hunger. And it’s not just
subjective effects. In this famous study,
Mind Over Milkshakes, if you offer people
2 milkshakes, one described as indulgent—
decadence you deserve, the other sensible—
guilt-free satisfaction, people have different
hormonal responses to them even though they
were being fooled and given the exact
same milkshake. And finally, maybe it was just
that the soup was hot and warmer foods may
be more satiating. So how do we figure out if
the solution to the soup mystery was time, thought,
or temperature? If only this study had
a third group. They had a solid eating group,
and a liquid drinking group. If only they had a liquid
eating group too. And they did. They also offered the fruit
smoothie in a bowl cold to be eaten with a spoon—
very unsoup-like, so if it was thought
or temperature the fullness rating
would be down by the liquid drinking,
the smoothie, but if it was just the
slowed eating rate that made soup as
filling as solid food, then the number would be up closer
to the solid eating group. And it was
exactly as high, meaning the only real reason
smoothies aren’t as filling is because we
gulp them down, but if we sip them slowly
over time they can be just as filling as if we ate
the fruits and veggies solid. Wow, this study thought
of everything! You don’t know
the half of it. They also wanted to see if it
would work with high fat smoothies. So what, almond
butter or walnuts? No, the LF drink was a
liquefied fat smoothie of steamed pork belly. I guess sometimes smoothies
can suppress your appetite.

100 Comments

Add a Comment

Your email address will not be published. Required fields are marked *