Although it's widely accepted that insulin at least functions to promote fat storage, and is known as a fat sparing hormone, this idea still has its critics. So instead of just presenting evidence to show that insulin indeed promotes the storage of fat, like for instance referencing studies that show increasing insulin levels leads to increased fat storage, I want to have a look at the other side as well, as the goal here has to be to seek truth, not just promote a certain viewpoint.
I happened to be reading this article today which does seek to dispel this role of insulin, in spite of all the challenges. So I thought it would be good to present it to you and then go over the points that it makes to see if at least some of them have merit.
It's certainly true that it insulin isn't the only thing that makes you overweight, but it certainly plays a major role, a huge role, although this role does conflict with the view that this has something to do with calories, that this is a matter of energy expenditure, calories taken in and calories expended.
I always felt this view was absurd actually, even back when I first became interested in health topics on the early 1980's. I remember my wife wanting to lose weight back then, and like just about everyone back then, and just about everyone today as well, she thought that this was a matter of calories.
So I increased her calories but reduced her carbs and the diet worked beautifully, she was amazed, I wasn't though because even back then I had enough of an understanding of this and the main point is that you don't reduce the mass of anything by way of oxidation (burning.)
So what happens instead is that we store certain amounts of what we take in, and while improving your metabolism and not overeating can to some degree improve this efficiency and make us store less, it's the mass of what we store and what we eliminate that determines our weight, and we can know this with absolute certainty in fact because the mass of things don't change.
So to try to break the theory of insulin, the article claims that regardless of what you store, you will burn a certain amount of calories, which will involve burning fat as well, so storage doesn't matter.
We need to step back here though and look at what the heck they mean by burning. This involves oxidation, and when it comes to fat this means lipolysis, which is the breakdown of fat into glycerol and free fatty acids.
So now you have these components floating around, now what? This is where their story ends but the story does not end here. In fact when this happens, the free fatty acids are liberated but they are now available for cellular uptake again. If insulin is high, that's exactly what will happen. So you can liberate fat by burning so to speak, and burning is a poor word here since it implies a reduction, cleaved is better but then the stuff can just find their way into the cells again.
High insulin also inhibits lipolysis, so when it's high you just have less of this going on, and with the amount that does escape, insulin is ready and eager to just put it back.
It seems to me that these people are also looking at people with normal insulin levels and not those who have high levels, from the way they describe things, especially saying things like insulin just acts in a cycle, with its normal peaks and valleys, and while it is resting things can return to normal.
If you have high insulin levels though you don't really see this, the area under the insulin curve, in other words your overall insulin levels, grows significantly. It is true that normal levels of insulin are not designed to make us obese, but we're not talking about normal levels here, and we aren't really talking about carb intakes that our bodies have evolved over the course of the history of the species to be able to deal with effectively.
So the article goes on to continue to focus on fat burning as if this occurs naturally with high insulin, like for instance exercising being helpful here, and it is to some degree, but it's far from an antidote, and all you have to do is look at the studies where increased exercise is the variable and you see very paltry weight loss at best. Exercise in itself is almost useless in combating obesity, and it's because insulin is the big culprit, not lack of exercise.
The discussion really goes downhill though when they say that the success that low carb has with weight loss is due not to carb reduction, but to increasing protein. It even claims that one of the ways it does this is to increase energy expenditure. That's all ridiculous, energy expenditure and calories for that matter have very little to do with one's body weight and low carb works even better when the protein is set lower than normal as well.
Finally, the article mentions leptin, which is indeed a factor in all of this, but insulin is an even bigger factor, and the fact that leptin, and high levels of it with leptin resistance, influences obesity isn't really in doubt, it surely affects appetite and appetite does have something to do with all this, but this does not cast any doubt at all on insulin's role.
I actually like some of obesity researcher Stephan Guyanet's work, especially his discussion on insulin resistance which is very good indeed, but in my view anyway he is still clinging to broken theories of metabolism and obesity way too much, the idea that this is a matter of calories which requires us to try to pretend that insulin isn't really the body's primary storage hormone. The caloric theory of obesity does indeed conflict with the insulin theory, but that's not an argument against it, and we can't say things like insulin can't be a big deal because we know burning calories is a big deal, that's a circular argument.
So it's not time quite yet to stop blaming insulin for fat storage, and in fact, we need to be blaming it a whole not more than we now do.