In my bestseller How Not to Diet, my chapter on fat-blocking foods

starts out with a command to Eat Your Thylakoids, doctor’s orders.

What the heck is a thylakoid?

Just the source of nearly all known life—and, the oxygen we breathe.

Thylakoids are where photosynthesis takes place,

the process by which plants turn light into food.

Thylakoids are the great green engine of life, microscopic

sac-like structures composed of chlorophyll-rich membranes

concentrated in the leaves of plants.

When we eat thylakoids, when we bite into a leaf of spinach,

for instance, those green leaf membranes

don’t immediately get digested.

They can last for hours in our intestines,

and that’s when they work their magic.

Thylakoid membranes bind to lipase.

Lipase is the enzyme our body uses to digest fat,

so if you bind the enzyme you can slow fat absorption.

It’s like a natural version of the fat-blocking drug Orlistat,

but without the anal leakage.

This is because the effects of the thylakoids are temporary.

Unlike the drug, the thylakoids do finally break down,

eventually freeing the lipase enzyme to do its job

before fat comes spilling out your other end.

Ultimately, fat absorption is not so much blocked

by thylakoids as it is delayed.

If all the fat is eventually absorbed, what’s the benefit?

Location, location, location.

There’s a phenomenon, known as the ileal brake.

The ileum is the last part of the small intestine

before it empties into your colon.

When undigested calories are detected that far down our intestines,

our body thinks we must be full from stem to stern,

and puts the brakes on eating more, by dialing down our appetite.

This can be shown experimentally.

If you insert a 9-foot tube down people’s throats

and drip in any calories— fat, protein, or sugar,

you can activate, the ileal brake.

Then sit them down to an all-you-can-eat meal,

and compared to the placebo group who had just gotten a squirt of water

through the tube, they eat over 100 calories less.

You just don’t feel as hungry.

You feel just as full, eating significantly less.

That’s the ileal brake in action.

So with thylakoids delaying calorie absorption until

that tail end of the small intestine, strong satiety signals

are sent to the brain, which dials down your appetite.

If you feed someone a meal with added thylakoids

(by slipping in some powdered spinach)

and measure the level of hormone release into their bloodstream

over the next six hours you see a significant rise

in a satiety hormone called CCK

and a drop in the hunger hormone ghrelin.

Does this then translate into a drop in appetite?

Researchers were eager to find out.

Spinach extracts were disguised in jam or juice to sneak thylakoids

into meals, and those unwittingly eating the equivalent

of about a half cup of cooked spinach felt significantly less

hungry and more satiated over the next few hours.

Give someone the equivalent of a shot of wheatgrass juice

in the morning, or what they might get in a “green drink”

or green smoothie and not only do they feel less hungry,

more satiated, their cravings for presented salty, sweet,

and fatty snacks, for example, potato chips, gummy bears,

chocolate, and cinnamon buns drop by about a third.

Feed them candy anyway and those who unknowingly had been snuck

some spinach report liking the sweets significantly less.

The satiating power of greens has been attributed to their

high water and fiber content and low-calorie density,

but the thylakoids may be their secret weapon.

Most thylakoid trials have shown improved satiety,

but the real test is weight loss.

Researchers in Sweden randomized overweight women to blended

blueberry drinks every morning with or without “green-plant membranes”

(in other words, just covertly slip them some powdered spinach)

and they get a boost in appetite-suppressing hormones…

a decreased, urge, for sweets.

Yes indeed, spinach can cut your urge for chocolate.

Check this out: 7 hours after eating spinach you’re like, chocolate?

Eh.

Got any more spinach?

And… boom, accelerated weight loss, all thanks to eating green—

the actual green itself, the chlorophyll- packed membranes in the leaves.

Within 12 weeks the women who were slipped spinach lost 11 pounds,

significantly more than the control group.

and as a bonus

their LDL cholesterol dropped too,

even before the weight loss started kicking in.

If you instead fix their calorie intake to force the same weight loss,

those randomized to the spinach group may have an easier time

with eating less, experiencing less hunger

after a test meal after weeks eating green.

Extracts of spinach were used in these studies

so they could create convincing placebos,

but you can get just as many thylakoids eating about a half cup

of cooked greens, which is what I recommend people eat

at least two times a day in my Daily Dozen checklist

of all the healthiest of healthy things

I encourage people to try to fit into their daily routine.

Which greens have the most?

You can tell just by looking at them.

Because thylakoids are where the chlorophyll is,

the greener the leaves the more potent the effect.

So go for the darkest green greens you can find,

which in my area is the lacinato or dinosaur kale.

What happens when you cook greens?

Blanched for 15 seconds or so in steaming or boiling water

they actually get brighter green but then if you cook them too long

they eventually turn a drab olive brown.

When you overcook greens the thylakoids physically degrade,

along with their ability to inhibit lipase.

But within that first minute or so when the green gets even

more vibrant, there’s a slight boost in fat-blocking ability.

So you can gauge thylakoid activity in both the grocery store

and the kitchen with your own two eyes.

The best green vegetable, though, and the best way to cook it

is whichever, and however, you’ll end up eating the most.

We have been chewing on leaves for millions of years,

but today the greenest thing about some people’s diets

may be a St. Patty’s Day pint.

Americans have averaged less than two grams of spinach a day,

less than half a teaspoon.

Your body was designed to have thylakoids passing through your system

on a daily basis, so the delay in fat absorption

can be thought of as the default, normal state.

It’s only when we eat greens deficient diets does the accelerated

fat digestion undercut our natural satiety mechanisms.

In the journal of the Society of Chemical Industry,

a group of food technologists argued that given their

fat-blocking benefits “thylakoid membranes could be incorporated

in functional foods as a new promising appetite-reducing ingredient.”

Or you can just get them in the way Mother nature intended.