research can improve your health.

Ketogenic diets ignite furious debate.

Keto has been promoted as a magic bullet for weight loss by its supporters.

And slammed as dangerous by its opponents.

It's no surprise, that completely removing almost all carbohydrates is not what most

people consider a balanced diet.

With carbs off the table, and on keto, we still need to find our energy somewhere.

This means a dramatic increase in fat intake.

At the same time drastically reducing carbs means starving our gut microbes of the fiber

that feeds them.

Nonetheless, doctors prescribe keto diets to treat people with severe diabetes and see

dramatic improvements and many healthy people swear by keto for weight loss.

On top of this removing carbohydrates prevents blood sugar spikes and crashes, linked to

inflammation and disease.

On today's show, we want to ask what the latest science says.

Are keto diets a crazy fad or could keto be right for me?

To help answer this question, I am joined by a leading nutritional researcher, Christopher

Gardner, a professor at Stanford University and a member of ZOE's scientific advisory

board.

Christopher is excited to share the results of his landmark clinical trial of keto diets

published this week in the American Journal of clinical nutrition.

You'll find links to this paper in our show notes.

Christopher, it's always such a pleasure to spend time with you.

And I'd like to start with our regular quick-fire round of questionnaires that our listeners

are sort of used to now.

So let's kick off.

Can you improve your health on a ketogenic diet?

That's complicated because there are good and bad ketogenic diets and there are good

and bad normal diets.

I can imagine a ketogenic diet that's healthier than some people's regular diet if you followed

it a certain way.

So we'll have to come back to that.

All right, so it's complicated.

Can you lose weight on a keto diet?

Absolutely.

It's a very restrictive diet.

For the things that are still allowed, the palatability will run out quickly and you'll

say, I am hungry, but not for that.

So nope.

Not gonna eat.

Lowered my calories.

Lost weight.

Is keto a good diet for most people?

I'm personally opposed to it because of its absence of grains and fruits and beans, which

don't seem justified to me.

So I don't think in the long run that it is, it's great for getting rid of added sugar

and refined grains.

Is doing keto from time to time helpful?

I'm opposed to anything that isn't a diet pattern that you'll follow for life.

I'm opposed to things that are just transient, I'm gonna do this for a while and it's a diet

that I'm going on, and then I will go off the diet when I got where I wanted to be.

Well, if you go off it, then the other stuff comes back and it was useless.

What's the biggest misconception about the ketogenic diet?

That it's high meat.

People think it's low carb.

And what has low carbs?

Oh, well, meats have low carbs, but really the ketogenic diet is a high-fat diet.

If you end up eating a lot of protein, then you've met your needs for the day and you

convert your proteins into carbs and fats, and whoop.

You threw yourself outta ketosis by making carbs outta your protein.

That's amazing.

And I did not know that.

Thank you, Chris.

The final question will cutting out carbs.

Stop your body's ability to process them?

No.

That was simple.

All right.

Well, look, I'm really looking forward to digging into those answers more, the whole

topic of ketogenic diets ignites furious discussion.

And I think a lot of confusion, I personally have never tried it because of the idea of

giving up bread and croissant for good, I just know that's a step too far, but as someone

with bad blood sugar control, I know there's some impressive evidence that keto can help

people with diabetes come off insulin.

So there's some real clinical evidence that suggests there's something interesting there.

And so I think it really fascinating, Christopher, for you to take us through this, and maybe

we could just start with what is a ketogenic diet and how does it work?

Sure.

So the ketogenic diet actually goes back 50 years as a diet that was used to treat epileptic

seizures.

It's been around for a really, really long time, but it's really odd that people are

now taking this and doing it for weight loss and some athletes are trying it.

And it's certainly relevant in the world of overweight obesity, and diabetes, because

a lot of that has to do with excessive carbohydrate intake and the inability to process those

carbs.

So if you wipe carbs outta your diet, if you go to extremely low levels, other than some

above-ground vegetables, and maybe some berries, you can resolve some insulin resistance issues,

and you will lose some weight.

So there is some basis of interest in this, especially given how many simple and unhealthy

carbs people eat these days, but a central component of our discussion, Jonathan should

be good carbs versus bad carbs.

Brilliant.

And before we go on to that, because you mentioned the word ketosis before.

Can you explain a little bit more beyond just this idea that I'm not eating carbs and I'm

eating fat?

What is this ketosis, what is going on inside my body as a result of following this diet?

If you think about this, the normal person on an average day is gonna burn a combination

of carbohydrates and fats all day long.

I think everybody, at least in the US learns this phrase.

The mitochondria are the powerhouse of the cell.

That is the basis of biology in the US.

I think my son told me he learned that this month.

So there you go.

I think it's universal.

I think it's universal.

And it has to do with the thing called the Kreb cycle or the TCA cycle is another name

for it.

So you've lost me now.

So, so explain.

It's a cycle where carbs feed in at one end and fats feed in at the other end.

Carbohydrates are usually 5 or 6 carbon atoms bound together.

And fats are anywhere from 4 to 26.

And you feed in as fats break down little 2 car units and you feed in as glucose breaks

down little 3 and 4 car units, and you spit out carbon dioxide.

You breathe in oxygen and as you breathe in oxygen, you breathe out CO2.

What happened?

Ugh.

You added carbon to the oxygen.

You just breathe in.

And in doing that every time you break carbon bonds, you make energy.

So glucose and fat all day long is what people burn.

If you stop eating carbohydrates to a very low, low, low level, then this cycle stops

running.

And these little two carb units of fats that are breaking down to provide you the energy

that usually gets burned together with carbs, start to pool up, and they have an alternate

path.

They make ketones.

They make four carbon units and these four carbon units can be broken down into single

carbs and can generate energy.

But it's in a slightly different pathway that excludes the use of carbohydrates.

And a lot of people probably do this actually overnight.

If you haven't eaten for 6, 8, 10, or 12 hours, some of your carbohydrate stores are used

up.

And so overnight, most people probably make some ketones.

Over the course of teaching nutrition, we say, you know, really is healthiest to have

carbs and fats burning together.

There's a blood-brain barrier.

The blood-brain barrier in the central nervous system doesn't like to burn fats.

They really prefer, and almost exclusively can only use glucose because that's what will

get into the cells.

But in the absence of glucose, if you had to these four carbon units that are ketones

could feed the brain and they could feed the central nervous system.

So now there's this movement, oh my God, maybe it's even better.

The keto folks are saying, oh God, maybe ketones are even better than glucose feeding the brain

feeding the central nervous system.

And that was sort of a pivot point in trying to think, could you just burn fat instead

of burning carbohydrate and fat together, which is the usual recommendation.

Got it.

So it's an unusual situation to be in for our sort of normal historical diets to be

in this ketosis.

That is my strong opinion.

Got it.

So why have people become interested in this?

You mentioned that 50 years ago, they looked at this for epilepsy.

That's a long time.

Why the discussion today?

Sure.

I would just speculate that it's part of this ongoing whiplash about low-fat diets, not

being the best thing for us.

And so maybe it should be low carb.

Maybe it should be lower carb.

Oh my God, maybe it should be extremely low carb.

When you use the terms low, fat, and low carb, you need a qualifier to go with that.

Is low, lower than yesterday?

Is low half as much as you had before?

Is low 75% or 25% of what you had, but it's quite undefined.

What do low carb and low fat mean?

And so Jonathan, when we go to the literature and I'm trying to pool studies together and

say, oh, let me summarize all the low fat, low carb studies.

Oh my gosh.