Sadly, this is wrong for a myraid of reasons.

I agree that hormones are important and that there is a lot of issues with the way people are eating nowadays, but the moment you claim that Low Carbs, High Fats (LCHF diet), Intermittent Fasting (or any other diet for that matter) is the way to solve it... you're becoming part of the problem.

You said "that hormones is the language of our body and we're speaking calories". Well, that's a great way to frame it.

Ironically, we can't grab calories, right?

They are not something we can use, but rather a way of measurement... or said in another way, it's a way of measuing the thing we want, not the thing itself. We can't grab kilometers or Celsius either.

Plus, saying that insulin is the hormone that's responsible for fat loss is partially true, and innaccurate at the same time.

As I said, hormones are important. Ghrelin, leptin, insulin... all of them matter.

The issue is to attribute hormones (let alone, a specific hormone) to be the one that's causing us to either gain or lose weight.

"The only currency the body really cares about is insulin. If you want to lose weight, reduce insulin. If you want to gain weight, increase insulin."

It's funny you mention that the Glycemic Index of food is somehow relevant... but that goes totally against what the literature says.

When protein and calories are equated, it doesn't really matter ... and there has been a myraid of studies (over 30 studies!) that have shown over and over again the same conclusion.

Look, there's no point in telling people that they can lose weight with "The secret of fat loss" - as your book says - if they can't sustain it.

That's the most important thing in anyone who follows any diet.

Yes, people have lost weight with IF and a LCHF diet... that doesn't mean they are the miracle solution to fat loss.

It just means you're creating a caloric deficit for them to lose weight.

And BTW, if you want to prove your theory of "calories not being the currency of the body", I accept that.

However, the real currency isn't calories or insulin... it's glucose.

And if you want to prove your point of calories being useless for fat loss or weight gain, then you can try and add 15g of olive oil (I'd say a burger instead, but seems that's not what you're after) in every meal you consume... and if you don't gain some weight in about 2-3 weeks, then I might even change my religion :)

PS. I know I came late to the party... but I just received the invitation.