The important question

By defining overweight as excess storage of energy in fat tissue (and consequently to little use of energy from the same tissue), we are only one simple question away from understanding what causes overweight and obesity, and ultimately how to treat and prevent it.

What factors control storage and release of energy in fat tissue?

Believe it or not, but this is actually common knowledge in physiology. Any physiology textbook will give you the answer, and the answer is even right. There are two main factors responsible for the storage of and consequently the use of energy in fat tissue. These factors are glucose and insulin, or more accurately the amount of glucose being metabolized and the level of glucose and insulin in your blood. Glucose is what most dietary carbohydrates are broken down to in your body and is what is known as blood sugar. Insulin is a very potent steroid hormone largely responsible for controlling blood sugar levels.

In order to understand how glucose controls storage and release of fat we need to understand how fat is stored. Fat is used as energy in the form of free fatty acids. These are long hydrocarbons that are broken down to create energy. When animals (humans are also animals) store energy for later use, it is mostly in the form of triacylglycerols in fat cells. Triacylglycerol is made up of three fatty acids bound to a glycerol molecule. So when the body has excess fatty acids that can be stored for later use, they are transported into the fat cell where they are bound to glycerol to form triacylglycerol (a.k.a. triglycerides). So far, so good. This all makes sense in that our fat tissue is supposed to work as an energy storage for when less food is available. Fat tissue is thus a very important evolutionary mechanism that ensures survival when food availability is not constant.

The thing is that for the body to make triacylglycerol, a molecule known as alfa-glycerolphosphate (glycerol-3-phosphate) is needed to provide the glycerol backbone of triacylglycerol. Alfa-glycerolphosphate is made in the body when carbohydrates are broken down. To put it simply, if little alfa-glycerolphosphate is made, fat tissue will lack glycerol molecules to make triacylglycerol and the fat cells cannot store energy. When the fat cells aren’t storing energy, they are more likely to release energy that can be used instead of dietary energy.

But the fat tissue is not only an important energy storage, it also functions as an important regulator of blood glucose levels. Glucose is not only providing the glycerol backbone for triacylglycerols, but is also made into fatty acids. This way, the fat tissue will absorb blood sugar when or if it gets high. This function is especially important when skeletal muscles are insulin resistant and absorb little glucose. If blood sugar is dropping the fat tissue releases fatty acids for use as fuel by the cells that can metabolize fat, thus making glucose available for the cells that need this particular fuel. There are some cells in the body that depend on glucose for fuel, but the total amount needed is so small our body can make it from scratch even without getting any dietary carbohydrate.

I am talking a lot about glucose and insulin, but what about how much we eat? Doesn’t that also control how much is stored? No, it doesn’t, it’s actually the other way around. How much you consume depends on how much is stored. It’s a complicated topic, but there are two important things I’ll say now and I’ll elaborate later. Firstly, energy expenditure and energy intake are highly dependent factors. This means that messing around with one factor will cause a compensatory change in the other (more elaborate in Norwegian here:http://www.forskning.no/artikler/2009/januar/207538 and in English here: http://nymag.com/news/sports/38001/). It’s the same in all animals. Secondly, our sensation of hunger is largely regulated by the energy available for (or rather the energy metabolized by) the liver cells at any moment. The amount of energy available for these cells does not necessarily reflect the amount of energy consumed. Worst case scenario, parts of your body might be starving despite large energy stores in fat tissue. Even though we might have a lot of energy stored, it doesn’t mean this energy is available for use.

Let us sum this up. Overweight is a condition characterized by excess storage of energy in fat tissue. The main regulators of storage in and release of energy from fat tissue are glucose and insulin. Ah, we are closing in. Now we are only one question away from understanding overweight and obesity and what we can do about it. And this time it will work.

Defining overweight

The first thing I’m going to do in this blog is to explain what causes overweight and obesity. I’ll also explain what can be done about it. It will not be the old dogma of eating less and exercising more. It will be the truth this time. None of the theories described here are my own. I am merely passing on information acquired by others, although not without critical thinking.
Here is the first part of how to understand overweight using one definition and two questions:
If we are to understand overweight and obesity and all its related metabolic disorders, we need to have a clear understanding of what overweight actually is. Overweight is most often defined as above a specific body mass index. BMI tells us something about ones weight in relation to ones height. Although much criticized, BMI does have its use as an epidemiological tool, but must under no circumstances be used to define overweight at an individual level. The reason for this is simply that BMI does not differentiate between body tissues. I’ll come back to this.
Secondly, it is also important not to use the first law of thermodynamics as a definition of overweight. This law simply states that energy change equals energy gained minus energy spent. I might have to get back to the misuse of this law in discussions of overweight, but for a more thorough discussion here’s one in Norwegian:
For now it is enough to say that overweight cannot be defined by total body energy change, energy expenditure or energy intake.
After much thinking I have found that the simplest way to define overweight is to say that:
Overweight is excess storage of energy in fat tissue. (See, it’s bold so this is definitely important.)
This definition might seem obvious, but it is of utmost importance for the scientific discussion of overweight to keep in mind that overweight is related to increase in fat tissue mass. Not muscle tissue, not nerve tissue, not bone tissue. Overweight is all about the size of the fat tissue. I think few would disagree with this, but as we will see, this definition brings us much closer to understanding overweight than most other definitions.
I guess many would have asked about the obvious by now. «How much is excess storage?» Well, while this is a perfectly reasonably question, it really cannot and should not be answered in general terms. In any individual an excess storage of energy must be defined by that person’s situation. We cannot keep making up numbers that puts some of us in the overweight category and some in the normal category. Remember also that overweight (excess fat tissue) is not necessarily harmful in itself, neither is it necessarily visible. A thin looking person might have a small fat free mass and a high fat percentage, and may thus be termed overweight.
So remember, overweight is all about fat tissue (adipose tissue). So if you want to know what you can do about it, you need to understand the fat tissue. Reed on and I’ll try to ease your understanding.

The start of a yet another blog

So I thought I’d try this blog thingy out. It’s so modern these days.

This blog will be dedicated to my passion for health science and especially diet and exercise. It is, as you may have noticed in English, and not very good English at that. Although English is not my native language, it is more far-reaching than Norwegian and thus reaches quite a larger audience than just us Scandinavians. When it comes to my language, you’ll just have to bear with me.

The last thing the world needs right? Just another smart ass who’s just discovered science and is on a crusade to rid the world of ignorance. Or perhaps this is all just a substitute for therapy, a place to air ones thoughts and maybe get a pat on the back. I don’t know. I’ll try it out anyway. Because as we say in Norway: «Det er bedre å drite seg ut enn å dø av forstoppelse!» Hard to translate that one, so I’ll leave it to others.

Ok. Here goes…