How much does it cost us to digest what we eat, not in terms of euros but of energy? This answer is provided to us by the diet induced thermogenesis, a term that indicates not a process but the amount of energy that our body spends to absorb and use the foods we ingest. Let's learn more about what happens and how this quantity can vary depending on what we eat, but not only
Let's start with the fact that it usually speaks of fixed thermogenesis, and it is defined as the energy that the body spends on absorption anduse of food. There is also the optional one and together they represent the thermal effect of food, the amount of total energy we need to digest food. The thermal effect of food is recorded one hour after the meal and can be performed by indirect calorimetry.
How can we easily imagine, there are no absolute or reference values that are valid in all cases, the first aspect to be analyzed is the type of food eaten. Just to give a few examples, the much loved and hated carbohydrates have a thermal effect of 7%, lipids of 3% and proteins can even reach 35%.
When a person follows a regular and balanced diet, and also varies, on average it needs equal energy which corresponds to a thermal effect of 10% for a complete meal. It is clear that if you dine with meat only, absurdly, you arrive at a thermal effect equal to 30% of the caloric value of the meal, this is because it has to do with proteins that require an extra expenditure of energy, in addition to what is needed for digestion by default, to make sure that the liver is able to carry on the protein synthesis and the transformation of proteins into glucose.
I notice the effect that proteins can have on energy demand during digestion, high-protein diets have been developed that manage to slightly increase metabolism. This can be seen as an advantage, in a way, but it comes with a price: one structured nutrition in this way it very often induces a certain hepatic and renal fatigue which can lead to states of edema.
We also talked about optional thermogenesis, it is nothing more than the energy expenditure linked to the activation of the sympathetic nervous system following the ingestion of a meal. The thermogenetic response can be very different from person to person, those with a very mild one usually tend to gain weight more easily. Not spending a lot of energy, it tends to accumulate fat.
To try to increase the induced thermogenesis from the diet it is advisable to do physical activity after meals, not too intense: a simple half-hour walk is fine.
We immediately started talking about thermogenesis by linking our discussion to diet and nutrition because in fact it is a topic that interests many. But let's take a step back to understand in general what it means thermogenesis. It is nothing more than a process, yes, this time it is a process, which serves the body to produce the heat necessary to maintain a constant body temperature.
It is clear that we immediately think aboutsupply because we take energy in this way and almost all that we eat at the table is converted into heat through particular organelles present in cells: the mitochondria.
This process is a lot related to food and to what we eat but not only, there are other factors that can influence its course, the temperature, for example, since it is a parameter at the center of the discussion. When the cold arrives very logically, more energy is needed to keep the body temperature constant, but this is not the only case to mention. Let's think for example of stressful situations, they too can make us spend a lot of energy.
Adaptive thermogenesis is linked to the activity of the sympathetic nervous system, which through some hormones causes our body to increase heat production. In this process, the muscle and the liver play a fundamental role but another element is also important, the brown adipose tissue. This term does not refer to body fat as a whole but to a fraction of it which in adult men is about 700 grams and is found in the areas of perianal, pericervical, and heart fat, but represents about 14% of the metabolism. baseline.
Thermogenesis and obesity
We continue to talk about adaptive by exploring the links this process has with the obesity phenomenon.
There are many obese people who have a low thermogenesis compared to the norm, many studies show it and by virtue of this we have started looking for new molecules that are able to increase the thermogenesis of the obese. We already find sibutramine on the market which reduces the sense of hunger and also increases thermogenesis. A similar effect is given by ephedrine in association with caffeine but there are also other substances with a similar effect such as green tea in association with caffeine, Citrus arantium and capsaicin, a very effective derivative of chilli but which has annoying side effects, first of all gastric acidity.
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