Thread by @sambit_dash

Since this got some attention, and few asked for details, let me elaborate. People were like this is keto, you don't know gluconeogenesis?, we are without sugar since 5 years, etc. So first some basics. 1/ #biochemistry #diet #nutrition

https://twitter.com/sambit_dash/status/1453342379981692931

So, what happens when you have had dinner at 9 pm and slept off?
Okay, before that, the brain is a peculiar thing. Its preferred and predominant fuel is glucose.
The food takes roughly 4 hrs to be digested and assimilated. What supplies glucose after 1-2 am? #nutrition #diet

2 things:
1. We've stored glucose as glycogen in liver. So that gets broken down.
2. After few hours of that process, gluconeogenesis (process in which body makes glucose from 5 different things) starts.
They are overlapping processes, first major, second minor (to begin wth). 3/

Now,
i. Glycogen stores (about 70-75 gms) gets depleted gradually (8-12 hrs).
ii. Gluconeogenesis (let's call it GNG) keeps going on, rate slowly increasing.
Then,
You wake up and have breakfast. 😊
GNG reduces drastically, glycogen starts forming.
So far so good.. #biochemistry

Now, if you skipped breakfast (younger folks, happens all the time, right?), what will supply glucose?
Yes, GNG.
The rate will keep on increasing.
What will supply raw material for GNG?
Simply, fat and muscle breakdown (latter more as fasting continues). #biochemistry #nutrition

So, folks, those who were throwing gluconeogenesis as some exotic pathway that is made to serve as a panacea to all diet concerns, no. It's just another carbohydrate metabolism pathway, which occurs, like daily.

Now let's go to the diet, keto diet.
#nutrition #ketodiet

Okay before we go there, most dietary recommendations state the following (more or less) as the source of energy:
Carbs: 45-65%
Protein: 20-30%
Fats: 10-20%
Remember, the normal diet we take is usually a mixed diet, consisting the above. 7/
#nutrition #diet

Okay, keto now.
I'll skip the history, but it started in the 1920s.
Keto changes the above percentages.
Carbs - 5%
Protein - 20%
Fats - 75%
(Side note: hence the assertion made by the nutritionist on NDTV, and others, is wrong. 20% carb will change the story). 8/

What does such a change do?
It creates the situation of starvation.
Weight loss occurs on account of two things:
Fat loss, muscle loss.
Less carbs creates that situation. Increased fat breakdown produces something special: ketone bodies. (Sorry can't get into those details). 9/

As in prolonged starvation, ketone bodies take the primary role in providing brain the primary fuel, because glucose isn't available.

If one is following keto diet, there has to be certain level of ketone bodies (can be checked in urine. How many do?), else it's pointless. 10/

Some criticisms of #ketodiet:
1) In a meta analysis of 32 controlled diet studies (trust me, there are several problems with diet studies as such) keto diet was shown to reduce extra 1 kg weight compared to high carb low fat diet. 11/ #nutrition

Some folks came at me telling diabetes is cured (Erm, no comments) by such diets.
2) Another meta analysis (there's a reason am not cherry picking on standalone studies) showed there is no difference in glycemic control in keto vs low fat diets. 12/ #diet

3) The lipid profile in keto diet is something much is not known about (I like how people just casually throw the term 'tons of data'). Bad cholesterol, or LDL is shown to increase in various studies. 13/

4) For so much that is discussed about #gutmicrobiome (microorganisms in intestine), #ketodiet has negative effects on it, added to GI side effects (30-50% of people) and requirement of supplements like vitamin B family, fibers, etc. 14/ #nutrition

That said, it is not to discredit #ketodiet. For weight loss in a certain range of obesity, for difficult epilepsies, it works and is desirable.

The problem rather is with the casual throwing around of this diet to all and sundry. 15/ #nutrition

Now the question arises, is a very low carbohydrate diet (VLCD) or #keto diet easily adaptable? (VLCD and keto are different but am clubbing them just to make it easy)

I'll cite 2 examples, of two different set of people. 16/

First, in the harsh cold Alaska, the native Inuit people, eat very very little carb. But they are adapted, that is they show some genetic change, to prefer ketone bodies as fuel.
Others are not Inuit. 17/ #nutrition #keto

That said, the mutation prevent ketosis to occur in Inuits.

Second, people in Blue Zone communities (7 places in the world, people live much longer, quality of life is better, Japan, Greece) obtain more than 50% of their caloric needs from carbohydrates. 18/ #nutrition #keto

Circling back to the original tweet about PCOD; suggesting #ketodiet is dangerous. Yes, often obesity is linked and it's desirable to all lose weight.
But, there are multiple hormonal changes occurring when body shifts from glucose to using ketones. All these can play havoc. 19/

There's so much more to write but not for a Twitter thread. Closing remarks:
- Evolution has made glucose the preferred energy source for humans.
- Some carbs, refined and simple, are bad, no two thoughts about it.
- There is also a case to reduce carb content in diet. 20/

In nutrition (a pretty young science at around 100 yrs), the phrases keep-it-simple-stupid & less-is-more holds good.

Often, all new fad diet planners as well as followers don't understand the basic science. Back to basics should be mantra. 21/21
#nutrition #diet #biochemistry