Sunday, 20 January 2013

Thermogenesis: The diet-induced thermogenesis


Thermogenesis means production of heat. Thermogenesis is a term which in the context of biological organisms is applied within the concept of thermoregulation.
Thermoregulation is a mechanism prepared by biological systems, in our case from the human being, in order to ensure a constant temperature of liquids and biological tissues.
This condition is met through the provision of mechanisms of thermogenesis and thermolysis, where for thermogenesis refers to the production of heat and for thermolysis heat dispersion.

Thermoregulatory mechanisms

A typical example of practical realization of these thermoregulatory mechanisms are the production of heat (thermogenesis ) on the part of the body in cold environments and, instead, its dispersion (thermolysis) in climates with high temperatures through the appropriate and specialized physiological activities to what responsible (peripheral vasodilation, polypnea, sweating).

Diet and thermogenesis

The concept of thermogenesis is now necessary to couple to diet in order to understand under what conditions the physiological and metabolic activity of the full term "diet induced thermogenesis" refers to.
This is the energy loss that the body makes in response to the introduction of energetic material (food).
The understanding of this phenomenon and its quantitative discrimination on the basis of qualitative contributions of nutritive molecules (proteins, carbohydrates, fats) is able to explain how certain dietary and nutritional approaches work better than others in the stimulation of lipolytic processes (ie, weight loss) compared to other contexts nutritional isocaloric but different impression in the distribution of nutrients ( proteins , carbohydrates, fats).
To understand everything you need to make two assumptions dutiful:
One of the principles of metabolic energy transfer and a metabolic principles regulating the metabolism of the individual basis.

Energy transfer

The body gets energy useful for many metabolic functions (footprint relational motility, sensitivity, or basic: circulation, sweating, endocrine and exocrine secretions, thermoregulation, muscle tone, etc.). Conferred on it by the chemical energy present within the molecules present in fuel-nutritive food.
But the chemical energy released by the oxidation of the last elementary molecules: amino acids, glucose, fatty acids, resulting from cleavage of larger macromolecules (proteins, carbohydrates, lipids) is not directly used by the body.
The body is not able to use thermal energy to produce work. And then if the energy from the oxidation of these elements could be directly used by the cells would result in a bubbling of body fluids and tissues would burn.
Then the energy released by the oxidation of the last elements of digestion is coinvogliata within a molecule highly energy called ATP (Adenosine Tri Phosphate). The spin-off of its phosphate group free about 7 kcal. In more advanced stages of the energy transfer processes, ie in the aerobic phase of the synthesis of ATP, per mole of NADH (reduced) that is oxidized are obtained 3 moles of ATP. So from each mole of NADH oxidised, then has a net energy production of 21 kcal.
But in practice the total energy liberated by the oxidation of one mole of NADH is 52kcal.
This means that the energy difference between the net amount of energy obtained from its oxidation, stored in the form of phosphoric bonds in the molecule of ATP and therefore also usable and the total amount released (52kcal), represents the energy dissipated as heat. So the energy yield of the combined system of transport of the chain of electron-oxidative phosphorylation in the synthesis of ATP is equal to 40%.
Ie our body presents an efficiency of 40% in changing the fuel chemical energy from food into useful energy to biological systems and to the mechanical work.

Basic metabolism:

The basal metabolic rate is the amount of energy required for performing neuro-vegetative functions to maintain an individual.
The basic metabolism in order not to be vitiated by factors of various kinds that can altering its quantitative values ​​must be evaluated in terms of: fasting food from 12-14 hours, fasting protein by at least 48 hours; rest psycho-physical (no physical activity and sensory), thermal neutrality (the subject does not have to put in place mechanisms of thermoregulation, so if you dress should be able to stay in an environment with a temperature of 18-20 ° C or naked at a temperature of 36 ° C).

The factors that affect changes in the basic metabolism are:

  • muscle mass;
  • muscle activity,
  • lifestyle,
  • style nutritional
  • age,
  • sex,
  • race,
  • specific dynamic action of food (TEF).
Our discussion will focus on this last point.
The specific dynamic action of food (ADS) represents the surplus of energy expenditure in the body in response to the introduction of nutrients. Proteins are able to arouse a caloric expenditure of 30% of the caloric introduced. For example 25g of protein determinants caloric intake of 100 kcal induce energy expenditure of 30 kcal.
It is seen that the calorie expenditure in response to the introduction of carbohydrates and lipids is much lower and more particularly of 2-5% for fat and 5-10% for carbohydrates. In addition, we investigated the possible mechanism responsible for the extra computing power led to the assumption calorie protein.
It is seen that the surplus energy expenditure in response to the introduction of protein was due to metabolic transformations such as gluconeogenesis, deamination, transamination, protein synthesis they faced basic nitrogen compounds resulting from protein digestion: amino acids.
This highlights how the extra caloric expenditure not due, as it was believed:
  1. to the processes of protein digestion since also the parenteral intravenous infusion of amino acids determined the same effects thermogenics,
  2. to changes in the alkaline reserve;
  3. in kidney stress since it was observed that at the level of the renal parenchyma oxygen consumption is not changed in response to the increased urea excretion resulting from protein metabolism.
Therefore, nutritional (maybe also combined with nutritional supplements appropriate) well-calibrated in the contribution protein, not only is able to favor the one hand the processes of protein synthesis at the base of deposition of new lean tissue (muscle growth) or of-preserving the existing one (anticatabolismo protein) but also, on the other hand, to induce thermogenesis which along with other aspects inherent to the frequency of training, level of training, intensity of training, type of training, the drops of life and other aspects of the nutritional environment contributes significantly to the process of weight loss and / or muscle definition.

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