How And Why We Get Fat
First off, overweight and obesity is a disorder of excess fat accumulation. The body’s storage mechanism is greatly enhanced and its oxidative capabilities are diminished. That means the body is really good at storing fat and making sure it can’t get out to be used as fuel. Obesity is NOT however, a result of excess calories and/or sedentary behavior.
The popular theory has always been that if we chronically over-consume calories, our bodies will store them as fat and we will gain weight. Also if we don’t get in enough activity, we might not burn enough calories and so will also gain weight. Try this…ask 10-lean individuals how many calories they consume daily. I guarantee you they have absolutely no clue! So, why is it they are lean if they have no idea how many calories they consume? How do they know they aren’t over-consuming accidentally? They are lean because their body is efficient at utilizing energy and not at storing it.
Another way to look at this is to think of a car. Imagine having to gas up every few miles, even though you have a full tank of gas. The gas is in the tank, it just can’t be accessed. That is essentially what is happening with someone who is overweight or obese. Its not that they lack will power or are lazy, their body is literally starving because it cannot access its backup reserves, and so eating more is the result. The eating more part is an effect and not the cause. The cause is a disorder of fat metabolism.
Now, fat metabolism is an extremely complex and nuanced process that is influenced by so many different factors it’s almost mind boggling! For example, as men age they produce less and less testosterone and as a result they develop visceral fat or the classic apple shape. This has completely nothing to do with how many calories they consume. It has very much to do with the fact that sex hormones interact with our fat tissue through the modulation of a very specific enzyme on the surface of the fat cell called “lipoprotein lipase”. This enzyme is inhibited in the presence of normal levels of testosterone in men, and stimulated in its absence. So, without making any dietary changes, simply increasing testosterone levels can lead to weight loss by itself.
Another example is the stress hormone cortisol. Cortisol is a hormone released from the adrenal glands via a signal from the hypothalamus, usually in response to physical or mental stress. Cortisol has many functions, but one major one is to stimulate the production of glucose in the liver properly termed gluco-neogenesis (creation of new glucose). What does this have to do with fat metabolism you ask? Lots! When the body sees too much glucose it stimulates insulin to drive glucose into muscle and fat cells. If this constantly happens than the cells become resistant to the effects of insulin and a whole cascade of bad things begin to happen, such as high blood pressure, diabetes, heart disease, etc.
So you see it is much more complicated than just eating too much and moving too little. It’s more about the signal the food we eat sends to the body that decides the fate of that food. This signal decides whether the food is sent to the muscles to be burned, or sent to the fat tissue to be stored. This “signal” is insulin. Insulin decides the fate of the calories we consume be it from fat, protein, or carbs. Total calories may play some kind of a role at some point or another, but remember the amount of insulin will effect how many calories we consume.
Insulin is the great orchestrator of a very complex (as you now know) system of metabolic and hormonal processes in the body. Insulin is made by the pancreas and one of its sole jobs is to move glucose and amino acids into cells to either be utilized or stored. This is the hormone type I diabetics lack and so need to inject to stay alive. In fact their body cannot store fat or utilize food energy without it! Insulin is incredibly important for life but also detrimental when produced to excess.
Insulin also works to drive up blood pressure by causing the kidneys to reabsorb sodium thus causing the body to retain fluid. This is only one way in which insulin can cause high blood pressure but there are actually 3 or 4 other ways all caused by excess insulin! So you see insulin has more than one effect in the body. One of the biggest, if not THE biggest role insulin plays is as the regulator of fat metabolism. Yes, that’s right. Insulin can be seen as the great regulator of fat metabolism.
As you know insulin works to drive glucose into muscle and fat cells, but you probably don’t know that it also works to keep it there. Like our sex hormones, insulin also interacts with that special little enzyme (lipoprotein lipase) on the surface of our fat cells and this enzyme specifically locks the door to our fat cells. So, once insulin is stimulated the fat cells take in energy or calories, and they are trapped and cannot be utilized for fuel until insulin levels are lowered. Does this kind of sound like the analogy above of the car with the full tank of gas? Exactly! The fuel is there but cannot be accessed until insulin levels diminish.
Lipoprotein lipase also resides on our muscle tissues as well and unlike fat tissue, is stimulated by the hormone glucagon and also epinephrine (adrenaline). The hormone glucagon is also released by the pancreas and has the exact opposite actions as insulin. Glucagon stimulates the fat cells to release free fatty acids and to be taken up by the muscles to be used for energy. Glucagon can be viewed as a “mobilization” hormone and insulin, a “storage” hormone. Glucagon also stimulates the liver to make glucose to maintain blood sugar levels, as the central nervous system runs almost exclusively off of glucose (and some ketones). Glucagon also causes the up-regulation of LDL(low density lipoprotein) receptors in the cells which is probably why cholesterol levels usually normalize on a low carb diet.
So, how does all this relate to the cause of obesity or overweight? Good question. Well, while there may be different initiators for obesity (depression, carbohydrates, thyroid issues, etc), if we understand how our fat tissue is regulated (mostly by insulin) then we have a starting point by which to begin attacking the problem.
If lowering insulin levels does not solve the problem then it is likely that no dietary approach will, and some medical alternative may be the only option if any at all.
The body releases insulin mainly in response to carbohydrates. Yes carbohydrates, and ESPECIALLY refined carbohydrates. These are sugar, flower, rice, whole grains, cereals, beer, fruits (oh yes!), beans, pasta, starchy vegetables! All the food that we were told was healthy for us. These foods illicit the biggest insulin response and so are the ones that are best avoided completely by the overweight, obese, or anyone who values good health.
These foods change the way the body partitions fuel and biases them towards storage. For example a diet of 2,000 calories of which only 10% (50 grams) are from carbohydrates is going to have a completely different effect than say a diet of 2,000 calories in which carbohydrates make up 50% (250 grams) or more. With the former the body will be utilizing fat as a fuel and will be creating its own blood sugar via glucagon and glycerol from fat and so will be mobilizing and burning up fat stores. With the latter, the bulk of calories will be stored because of the insulinogenic (producing insulin) properties of carbohydrates.
There is only about a teaspoon of glucose in the blood at any one time, and because glucose is toxic in high levels the body needs a way to get rid of it quickly. Insulin drives the excess sugar and triglycerides into the fat tissue anytime there is too much sugar in the blood. For example, when the body sees 40 or 50 grams of carb from one cup of pasta, the body converts this to over 14 teaspoons of sugar! Insulin levels spike and the liver converts the excess carbohydrate into triglyceride so it can be stored in the fat tissue. Because insulin levels have been elevated and calories were lost into the fat tissue, the muscles were never nourished. Shortly after, appetite increases because the cells still haven’t been fed. If more carbohydrates are consumed then this vicious cycle continues. So, while it may appear that an individual is getting fat because they are overeating, in reality they are overeating because they are getting fat. The calories that the cells need to be nourished are lost into the fat tissue and it’s almost as if they haven’t eaten at all.
Now, obviously there are some people who can eat carbohydrates to their hearts content and still not get fat. We all know a few of these individuals. What gives? Well, these fortunate individuals have genetics on their side. They don’t respond to carbohydrates the way the rest of us mortals do and so they remain lean. Every one of us was born with a greatly differing genetic level of tolerance to insulin and carbohydrate. The level of carbohydrate a lean person eats will very likely make an individual who is predisposed to obesity (thru their genetic intolerance to carbohydrate) fat. There is complete individual variability on this and this is not a one size fits all kind of thing. So, what makes one person overweight or obese may have no effect on the next person.
Lean individuals have very efficient fat tissue and likely produce less insulin in response to carbohydrate. It is likely that their liver is more efficient at metabolizing insulin and so the amount of time insulin spends in circulation is also likely shorter. Their fat tissue still accumulates fat but it comes out effortlessly and more quickly than in someone who is predisposed to obesity. This is why it appears they can eat what they want and not get fat. This also why it appears that the lean are more active than the obese, when in reality they have energy readily to burn and this drives them to move more, run, and take up sports. An obese person remains sedentary because they always are tired because their backup energy stores are literally inaccessible. Again, the causality here is reversed.
Well, that’s it in a nutshell…although 4 pages is hardly a nutshell. Sorry everyone. You have my respect if you all make it through this! -Kenny
Head Coach CrossFit Torque
BS Exercise Science
CrossFit Level 1 Trainer
CrossFit Olympic Weightlifting