Fasting insulin and weight loss and calories-in vs calories-out

I had this exchange in the comments on a previous post:


Frank said...

Hi Peter.

I'd say that I pretty much agree with your post. Insulin and caloric deficit are not mutually exclusive, ie, low-insulin could enhance fat loss on a caloric deficit or, looked from another perspective, a caloric deficit could enhance fat loss if someone has low insulin level. 

I have only one question for you. For the sake of it lets make thing black and white. 

What do you believe is the most important thing to do, in order to achieve weight/fat loss 

a) be in a caloric deficit (your insulin level does not matter much) 

b) having a low-insulin level (it does not matter much if you're in a caloric deficit or not). 

Again, in real life, I don't believe they exclude each other, but if you could fix only one to have a weight loss, which one would you fix? Calories or insulin? 

The way I see it is that, as you stated, insulin inhibits lipolysis, but more lipolysis does not equal more oxidation. It still has to be matched to energy expenditure. In that case, calories would be the most important factor. That's my point of view and it could be wrong. 

I'm just wondering if you agree to some degree with it, because reading your post, I get the idea that you do. 

Thanks for your time.


Peter said...

Ah Frank, now there is a question.

Without caloric deficit (and I want uncoupling proteins, sleeping metabolic rate, spontaneous movements, etc, etc, etc, everything, accounted for) there will be no weight loss.

But, in real life, if I could only alter just one, it would be insulin.

I would expect no weight loss but I would expect improved health.

What else matters?




There is a flaw in the answer I gave to this question. It's working at the Noddy level of calories-in vs calories-out.

The Noddy approach is perfectly adequate to explain the findings of GnK's paper (PR's weight loss excepted, if she genuinely ate all she was asked to), but embarrassingly stupid in the real world.

Let's look at calories-in vs calories-out in the fixed caloric phase of the Abredeen study.


Calories-in is total calories in to metabolism. There are two sources. Those from the diet, let's assume (incorrectly) these are genuinely all of the 2000kcal/d on offer. Then there is the supply of free fatty acids metered out from adipocytes under the regulation of insulin. Maybe a little glycogen, but I'll ignore that for the discussion.

Under LCHF conditions more FFAs are accessible due to lower insulin levels. More get used and, from Table 1, only 1930kcal of food are needed to supplement those calories-in from adipocytes in order to meet total metabolic needs. Hunger is low. Calories supplied are clearly able to meet voluntary calories out. Demand is within the limits of supply. Some food is refused.

Under MCMF conditions the higher insulin level allows less calories to be supplied from fat in to metabolism (adipose derived calories-in fall), so calories-in accepted from food spontaneously increase to the full 2000kcal/d. Under the study conditions we cannot tell if 2000kcal plus reduced adipose FFA supply is enough for as much metabolic activity as was possible under low insulin conditions. What if it is not? Now the real question is: Does lipolysis automatically increase to supply all needs for calories out? Why should it? Lipolysis is controlled by insulin. Insulin is high, lipolysis restrained.

If there is any shortfall in the calories from fat plus 2000kcal, there are only limited calories available to burn. You can't burn what you don't have. Calories-out would drop because they simply cannot exceed the supply available. I would expect the participants to automatically reduce their calories-out. There is no free lunch. Calories-out = calories-in. All need to be accounted for.

Is it be possible to force lipolysis in the face of hyperinsulinaemia to increase FFAs from fat to a higher level without lowering insulin?

Of course it is. There are other hormones in addition to insulin. You can throw around adrenaline, growth hormone, glucagon and probably a truckload of others I've not thought about. You can add in direct sympathetic nervous system innervation of adipocytes to effect lipolysis if you like. But these mechanisms come with a price. The price is hunger.

I think it's called working up an appetite.




In the Aberdeen study the attempt to maintain caloric intake failed during the LCHF phase because low insulin increased caloric supply from fat. Higher insulin in the MCMF phase limited calories-in derived from adipose tissue and may well have set a cap on total calories available for use during this higher insulin phase.


In Frank's thought experiment it might be easy to fix dietary calories-in, but people might refuse some of them if insulin was low enough for adipose tissue derived FFAs to be available.... If they ate all of their calories but wriggled in their chair a bit more because they had more calories available then the concept of calories-out being fixed is lost....



I'll just finish with a clarification of this phrase from another commenter:

"lipolysis is not beta oxidation"

This is, ultimately, accurate. That doesn't stop it being bollocks.

A rather more perceptive view is the situation comes from, of all places, the lipophobic cardiologists who published on FFAs and myocardial ischaemia:

"The rate of fatty-acid uptake and oxidation by the heart is controlled by their availability [33]"

Oh, interesting. Availability. A supply led system. Hmmmmmm. I would guess most FFA burning tissue would follow cardiac muscle. Now I can't quite remember what effect insulin has on lipolysis and FFA availability. Silly me.

Peter