By Lyle McDonald: www.bodyrecomposition.com

Don’t worry, slowly, I’m getting to the point.

So when you are in an energy deficit and/or losing body fat, leptin levels drop.

Although I haven’t talked much about the role of exercise here I’d only note that whether or not the deficit comes from caloric restriction or exercise per se doesn’t appear to have much of an effect on how much leptin drops.

Basically, the body appears to be sensing ‘energy availability’ (defined as energy intake minus expenditure) and adjusting things based on that. I’d, of course, note that exercise still plays plenty of other crucial roles (including psychological, which I am getting back to slowly but surely) in terms of dieting and fat loss.

In any case, what happens now?

By Lyle McDonald: www.bodyrecomposition.com

Ok, so now that you know what leptin is and a little bit about what regulates leptin levels, I want to look at what leptin ‘does’ in the body. The short answer is a whole lot of things.

Here’s the long answer:

Like most hormones in the body, leptin has effects nearly everywhere in the body. In skeletal muscle, it’s involved in promoting fat oxidation, it impacts on fat cell metabolism directly, liver metabolism, is involved in immune system function (which may be why dieters get sick when they get very lean) and more recent research is implicating effects on brain function, neurogenesis, breathing and a whole host of other stuff.

By Lyle McDonald: www.bodyrecomposition.com

In the Bodyweight Regulation: Leptin Part 1, I talked primarily about leptin (and a bit about insulin,and a very little bit about the other hormones) and its discovery and how it may be the (or at least one of the) long-sought after hormones involved in regulating bodyweight. Today I want to take a quick look at what leptin is and how it’s regulated. Next time I’ll look at what leptin is doing (or not doing as the case may be).

Leptin is a protein hormone released primarily from fat cells although skeletal muscle, the gut and possibly the brain releases it too. But, in terms of overall quantity, fat cells are the primary place where leptin is synthesized and released.

By Lyle McDonald: www.bodyrecomposition.com

As I noted Set Points, Settling Points and Bodyweight Regulation Part 2, although I’ve been using bodyweight/body fat during this discussion, it’s probably more likely that it is body fat levels per se that are being regulated. Today you’ll see why and from here on out I’ll only talk about bodyfat regulation.

With early research (I’m talking the 1950’s) having established the existence of some type of setpoint (again, primarily in animal models), early researchers had to sort of guess what might be going on in terms of regulating body fat levels.

Essentially they postulated that the brain of the animal must be responding in some form or fashion to a hormone that scaled with body fat levels. They could only postulate what it was and it would take another 40 years before a major candidate would make itself known.

In Set Points, Settling Points and Bodyweight Regulation Part 1, I took a little bit of a look at the issue of bodyweight regulation and the concept of the set point, examining various bits of research supporting the existence of such a thing. At the end of that piece, I also mentioned that not all researchers believe in the concept of a set point, feeling instead that a settling point is a more accurate representation of what’s actually going on.

Recall from Part 1 that the set point idea basically says that the body will attempt to defend some body weight (or body fat) level (or perhaps range) by adjusting things such as metabolic rate, activity, hunger, etc. in response to changes in weight or fat.

By Lyle McDonald: www.bodyrecomposition.com

Having explained why the separation of psychology and physiology is a false separation in Dieting Psychology vs. Dieting Physiology, I want to discuss quickly some of the physiology behind diet failures. This is a topic that I discuss in detail in nearly all of my recent books and I’m not going to spend endless time on it here (trying to eventually get back to the psychological factors behind diet failures).

A long standing debate in the world of obesity research revolves around the idea that bodyweight (or perhaps body fat) is regulated. What does that mean exactly?

By Lyle McDonald: www.bodyrecomposition.com

Over the next series of articles, I want to look at both physiological and psychological reasons that diets can fail.

But before doing that I need to make something very clear: the distinction I’m making between psychology and physiology is simply for convenience, it’s not one that really truly exists.

That is to say, psychology impacts on physiology and physiology impacts on psychology and the days of pretending the body and mind are separate non-interacting entities are long, long gone. Again, I’ll make the separation primarily for reasons of convenience, it will save me some needless complexity in the upcoming discussion. Just keep in mind that it’s an artificial and non-existent separation in reality.

By Lyle McDonald: www.bodyrecomposition.com

This is a very technical article that I wrote a while back for a now defunct online magazine. If you’re extremely interested in some of the underlying molecular level reasons ‘why’ certain things happen in the body, this is an article for you. If not, I’d suggest pulling something else out of the archive. There isn’t a ton of application to be had out of this article; as stated it’s more of a ‘why things happen’; at best, it will help explain some of the issues that go along with both dieting/fat loss and gaining muscle, along with a lot of the underlying physiology of my Ultimate Diet 2.0. I guess that’s something anyhow.

The molecule I want to talk about is called AMP-activated protein kinase or AMPk for short, a compound that is turning out to be one of the major metabolic regulators in the liver, skeletal muscle, fatty acids, and the brain. This is especially true if you’re talking about the regulation of glucose uptake and utilization, fatty acid intake and oxidation, and appetite. Ok, maybe I have your attention again.

By Lyle McDonald: www.bodyrecomposition.com

As much as I would rather continue talking about my dogs and the Austin Humane Shelter, I suppose it’s time to get back to writing about nutrition, training, fat loss and all of the rest. I’ll note that I do have a surprise coming up and I’ve added a permanent page for the Austin Humane Shelter to the site.

But between writing about my own training in Methods of Endurance Training: Results Part 5 and Methods of Endurance Training: Results Part 6 before the series on Volunteering at the Austin Humane Shelter, it seems like utterly forever since I’ve written about anything related to fat loss.  And since I always gotta move that product, that’s what I’m going to talk about today.

And since I’m a bit emotionally exhausted from the last week and a half of updates about the dogs, I’m actually going to try to keep this a bit short.  The question I want to address today is this: Does the diet determine the training or does the training determine the diet?  This isn’t really a direct question that comes up anywhere, but it is ultimately an issue that needs addressing as I hope you’ll soon see.

This is a situation that I usually refer to as square peg/round hole problems.  And by ‘I refer’ I mean this: I stole this concept from someone years ago and want to sound impressive by making it sound like I invented it.  Anyhow.  The basic issue is when you try to force an, err, issue.  That is, when you try to ‘make’ something work in a situation that it’s not suited for.  There are lots of these but here I’m focusing on diet.

By Lyle McDonald: www.bodyrecomposition.com

Question: I’ve long seen it claimed that cardio has to be done first thing in the morning on an empty stomach for optimal fat loss, is this true?

Answer: This is probably one of the most commonly asked questions which is why it’s worth addressing. It’s worth keeping in mind that this idea usually comes out of the bodybuilding subculture, usually contest bodybuilders who, assuming their diet is working properly, are getting towards the low-end of body fat levels.  And the short-answer to your question is that the body fat of the person is going to be the main determinant of whether doing cardio fasted in the morning is important or not.

To understand that, I need to cover a bit of background physiology, I’d mention that this is discussed in much more detail in both my Ultimate Diet 2.0 and The Stubborn Fat Solution for anybody who is truly interested in the topic.  But simply, there are three primary steps involved in ‘losing’ fat, they are: