Meet the hypothalamus, the hamster in your brain. A minuscule part of the brain, about as big as a sugar cube, in terms of calories. Although it is very tiny – less than one percent of the total brain volume -, it has enormous potential.
The hypothalamus is originally an ‘ancient’ area of the brain that doesn’t just occur in mammals but has also manifested itself in worms at an early stage. In humans, it plays an important part in the survival of individual persons, but also in humanity as a whole. Among other things, this area of the brain is involved in the regulation of body temperature, respiration, heart rate, procreation, and the sense of hunger and thirst. These processes are automated and take place outside of your own consciousness. They just happen.
Apart from this, an area of the hypothalamus is known as our biological clock.
The hypothalamus is involved in protecting the body against too large fluctuations. As a system, our body does not like major and rapid fluctuations. This also applies to the hypothalamus. It is a function that manifests itself in keeping your body temperature steady, for instance. This temperature will always be within demarcated values, in a normal situation. Although when it comes to monitoring body weight, the hypothalamus is mainly focused on preventing or repairing too rapid weight loss. This is in line with its function in prehistoric times, where the risk of a food shortage was far greater than the risk of an abundance of food. In light of that, it was crucial to strive for a positive energy balance; in other words, a situation where there was always just a bit more food coming in than being consumed. The extra food could be stored for leaner times, in the form of a fat reserve.
Our distant ancestors only had two ways of getting sugar; by eating fruit or honey. Nowadays, we do not need to make an effort to find some high caloric or sugar-rich foodstuffs. On the contrary, it is at hand everywhere and we can barely avoid it. The problem is that the hypothalamus is not aware of the existence of such things as supermarkets, and all the other opportunities people have to get their hands on food. Nor can it be trained or educated in this respect. This means it is not us who have suddenly changed, nor our brain, but our surroundings have changed much quicker than we can keep up with.
Therefore, the hypothalamus is still tuned to the energy surplus that used to be so important in the old days and will still perceive of rapid weight loss as a major threat. Actually, the hypothalamus has no real way of stopping the ‘intake’ of food. In the short term, the brakes will rather be applied when you get a congested feeling because your stomach is too distended. Or by your common sense (which resides in your prefrontal cortex, on which you can read more here), when you realise how much you have eaten. But there is no long-term safeguard within the hypothalamus against overeating.
When the hypothalamus perceives a shortage of energy, food, or fat, it will react. It will regulate things in the body in such a way that a person will use less energy on the one hand and absorb more energy on the other hand. It will make the body use less energy by lowering the basal metabolic rate, for one thing. This is the energy your body uses for all the processes that take place; your heart rate, your breathing, but also the movement of your intestines while digesting food, for example. These processes use a great deal of energy, and you don’t need to do anything yourself. Even if you lie in bed all day long, you will still burn the greater part of the food you ingest every day. In times of scarcity, your hypothalamus will greatly wind down this resting metabolic process. For instance, your heart rate and blood pressure will go down. Besides, the hypothalamus will stimulate your behaviour and sensations, in order to consume more food. One of these sensations is your sense of hunger, which will be greatly stimulated.
This means that the hypothalamus plays an essential part in keeping you alive but can also work against you if you want to lose weight, in spite of all good intentions. At one time, its function is in sync with your interests (that is to say, staying alive), but at other times it forms an obstacle for a totally different goal (which is losing weight sustainably). There are two sides to the proverbial coin.
Apparently, the hypothalamus has trouble distinguishing voluntary weight loss from a shortage of food. While you think you are doing a good job by quickly losing eight kilograms (which is the essence of a crash diet) just before the beach season, your hypothalamus will interpret this sudden decrease in the food supply as a sign of scarcity, of famine, an ice age even. Once summer is over, you may well lose some of your focus on losing weight or maintaining the same weight. But your hypothalamus will still be focused and undertake action. It will try to repair the effects of this disaster and try to influence the ‘hunt’ for food. Your brain and body will be directed towards food, against your good intentions.
Even worse: in order to make sure the body is better prepared for another period of such awful hunger and shortage, the hypothalamus will not only pull out all the stops to re-establish your old body weight, but it will also add some extra kilos. This is the well-known JoJo-effect.
The importance of slowly losing weight.
Now you have seen how poorly the body handles sharp changes, you will also understand that the hypothalamus will resist such rapid changes.
In order to visualise the concept of the hypothalamus, we chose to use a single image: the hamster. You know, the cosy little rodent that stuffs his cheeks full of food and also hoards a big winter supply. Imagine that you manage to sneak in and steal one seed from the supply. The hamster won’t notice and will still be content and friendly. But now imagine decreasing this mountain of food by taking big heaps away. The cosy hamster will develop into a stressed-out little bastard.
This is exactly the way in which you might regard certain functions of the hypothalamus. As a hamster with a large winter supply. If it concerns overweight humans, the winter supply consists of the extra kilos. And the hypothalamus does not like this supply to diminish. What’s more, it would prefer this supply to increase bit by bit.
Key Points in This Section:
• The hypothalamus plays an important part in the way our body handles food and nutrition;
• The hypothalamus is not ill, it just does what it is supposed to do;
• Do not lose weight too quickly, because angry hamsters always return!