The second question provides the answer

On our way to understand overweight we have (that is I have, but I thought you should be included) defined overweight as excess storage of energy in fat tissue and we asked the obvious; what factors control the storage of energy in fat tissue? The answer is glucose (a simple sugar that when it’s in our blood is called blood sugar) and insulin (a hormone). The reason glucose and insulin are the prime regulators of fat storage has to do with the function the fat tissue holds as a regulator of blood glucose levels and how insulin regulates energy storage.

We know that lifestyle factors affect fat storage. We get fat and thin by doing different things in life. We all know this. We get fatter during Christmas and lose weight (although usually not permanently) when desperately clinging to our new year’s resolutions. Scientists are talking about the obesity epidemic. If humans suddenly gain a lot of weight (and we are gaining weight) during a few decades, than we know for certain that it is caused by some lifestyle factor rather than by a genetic mutation or some other. So by asking the second obvious question we will actually know what causes overweight and also how to treat it or avoid it.

What lifestyle factors affect our glucose and insulin levels?

Although the answer to this is slightly more complex than the last one, it is also, from a scientific point of view, quite easy to answer. There are two main influencing factors. One is physical activity (also known as exercise) and the other is dietary carbohydrates. You might be thinking that this is some sort of Atkins tribute based on a positive personal experience with carbohydrate restriction. It is not. This is as strictly scientific as is gets, and neither Atkins nor any other commercial weight loss diet has anything to with this. Dietary carbohydrate is simply the number one lifestyle factor influencing blood sugar and consequently insulin levels thus increasing energy storage in fat tissue. In addition carbohydrate provides structural molecules for the formation of triacylglycerol.

So here it is. The answer. This is all somewhat simplified, but still as close to the truth as we can get. If you want to lose superfluous fat tissue, restriction of dietary carbohydrate and or exercise (doing both does give the best results) is the best way to do this. If you are gaining weight (as fat tissue) it means that you are taking in more carbohydrates than your body can use in your current condition. Exercise will make our body tolerate more dietary carbohydrates and trough its effect on skeletal muscles, will reduce the risk of high blood glucose levels. A fit muscle will absorb blood glucose much more efficiently than an unfit one.

Time for a small digression here. Remember that insulin is released in our body as a direct response to our blood glucose levels. Only carbohydrate (not fat, not protein) has any real influence on our blood insulin levels. Some carbohydrates increase blood sugar and insulin more than others. How large this increase is, is measured in glycemic index or glycemic load.

So, any factor that increases our blood sugar or insulin levels will increase the storage of fat and thus reduce the use of fat energy. Calorie restriction usually also causes a drop in glucose and insulin levels (largely because of lower total intake of dietary carbohydrates and a drop in the intake of the carbohydrates with high glycemic index), and will thus also often result in weight loss (although as it seems, almost never permanently). Many factors can affect our glucose and insulin metabolism. Dietary carbohydrates and exercise (most likely in that order) are the most important lifestyle factors. But other hormones such as thyroid hormones and cortisol also influence our glucose and insulin metabolism and thus our fat storage. 

Our body is immensely complex and in fact a whole range of factors may influence fat storage. The bottom line is that no matter the cause of an increase or reduction in fat mass, it must be explained through its influence on glucose and/or insulin metabolism.

I’ll try to sum up again. Overweight explained through one definition and two questions goes like this:
Definition: Overweight is excess storage of energy in fat tissue.
Q: What factors influence storage of energy in fat tissue?
A: The two most important are glucose and insulin.
Q: What lifestyle factors influence our glucose and insulin levels the most?
A: Dietary carbohydrates and exercise.

If you want to gain weight by increasing the size of your fat tissue, then you should lay back and relax. Be passive and eat a lot of carbohydrates, especially those who influence blood glucose the most. If you want to reduce the size of your fat tissue, do the opposite.

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…