With obesity on the rise in more and more countries and legions of diets with little results, if any, I had been thinking about writing something about proper nutrition and some of the key physiological mechanisms involved in human metabolism. It is a bit away from envisioning the future, although the fight against obesity will gain momentum in the years to come.
There are many misconceptions out there. For instance, we all have heard that carbohydrates are not good, fat is not good or meat is not good. This is total non-sense. Carbohydrates, fat and protein are good. Actually, they are indispensable to our health. What is bad is too much, especially too much of the nutritionally poor quality carbohydrates, fats and protein sources.
Obesity and overweight are increasing health issues. In the world there are about as many overweight people as they are people suffering from hunger: around one billion people in each group. What causes overweight? The answer is simple. A person gains weight when he/she ingests more calories than he/she burns. The cause can be either too rich a diet and/or not enough physical activity. In most cases, it is a combination of both. The source of unburned calories are metabolized into fat and stored in the fat tissues. This is a problem, because fat tissues are poorly irrigated with blood vessels. This makes the stored fat difficult to eliminate. The body will use calories coming from the meals before it uses the fat reserves. This is why it is so difficult to get rid of extra pounds. The only way to use the fat reserves is through long intensive physical activity.
Some might wonder why our body does not tell us when to stop eating. Actually the body does, through two physiological mechanisms. One is a mechanical mechanism. When the stomach is stretched, the nervous system sends the information to the brain that the stomach is full and the brain makes us stop eating. The other mechanism is biochemical, through the blood composition, the brain sensors can detect when we have ingested enough energy, and the brain makes us stop eating. We feel “full”.
This could make you think that we should never overeat because the brain would let us know on time. Theoretically, this is true but the modern lifestyle has found a way of deceiving the brain. The biochemical mechanism takes time to react. It needs to detect a glycaemia level high enough to act. When we eat food and beverages that are highly concentrated in energy, and therefore have a relatively small volume, we ingest more calories than we would need before the stomach gets stretched, and before the glycaemia level rises in the blood to the normal level. Such foods are generally low in fibre and high in fat, such as fried foods. Soft drinks are not filling and they contain many calories. You can imagine the result of a combo bacon cheeseburger-French fries-pop package meal! The carbohydrates that they contain pass in the blood almost instantaneously. One of the advantages of fibre-rich food, such as fruit and vegetables, is that they fill the stomach and contain relatively few calories per volume unit. This activates the mechanical nervous mechanism and limits our food intake much faster than foods with little fibre. Do not fool yourself! The little leaf of lettuce in your burger is not enough to protect you.
This brings me to talk about carbohydrates. There are two types of carbohydrates: the slow ones and the fast ones. The main representative of slow carbohydrate is starch. Starch is a long molecule that does not get into the blood stream as such. When we consume starch in bread, rice, pasta or potatoes, the starch gets cuts in a smaller component, called glycogen. The glycogen is stored in the liver where it waits for instructions from the brain to be released in the blood stream. This happens through a biochemical mechanism. The brain sensors detect a state of hypoglycaemia, and it orders the liver to release the glycogen. As long as our liver still has glycogen in store, we do not feel hungry. The system regulates itself smoothly. When we run out of glycogen, which is between 2 and 4 hours after the meal, we get into a hypoglycaemic state and we feel hungry. Usually it happens around 11.00 am and noon. That is why lunch exists! Same thing happens around 5.00 pm. Starch is good and necessary for us (as mentioned before, too much, on the other hand, is not).
The second group of carbohydrates, the fast ones, follows a different process. This group consists of what we call sugars, such as saccharose, fructose or glucose. When ingested, they do not get stored for later release, unlike starch. They flow into the bloodstream almost instantaneously and there are two possible scenarios. If our activity level is high enough when we consume them, they are burned to provide us with energy. If our activity level is too low for the amount we consume, our metabolism deals with the fast carbohydrates in only one manner: it transforms the sugars into fat that then get stored in the fat tissue. This is why drinking large amounts of pop or snacking on candy bars while sitting on your couch watching TV or playing video games will make you fat. There again, the rule is enough sugar to sustain yourself is good, too much consumption is bad.
About fat, I can tell a similar story. Within the amount necessary to allow all our functions to work properly, fats are fine. As their name indicates, essential fatty acids are indispensable. Even the dreaded cholesterol is an essential element for us. What is not good is to consume too much fat, and to consume too much of the less good ones. The length of the carbon chain, the level of saturation and the configuration of the molecules also affect your health. The excess of fat in your diet will end up as fat deposit in your body. This is why potato chips while watching TV will hurt you, too.
Protein is good, but with moderation as well. As for the other elements, too much protein can cause some problems, as protein stored in the intestine before release will not ferment, unlike fibre, but will undergo a rotting process, resulting in the production of harmful amines. The kidneys have also more work to do, and a long exposure to a diet too rich in protein may cause kidney problems.
So, what is the lesson from all of this? For me, it is that food one of the enjoyable things in life, as long as it is consumed with moderation (an incidental excess once in a while is fine, too; it means that you enjoy life) and it goes together with a healthy lifestyle. A person should have 7 hours of physical activity (the kind that makes you sweat) per week. Also, remember that the best is to not gain extra pounds in the first place, because the fat tissue is remarkably persistent.
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