August 31, 2009

The human engine

Nutrition is much more than just type and amount of food consumed-it is about the balance between fuel supply and expenditure.it is this balance which creates our real energy crisis.our human engine runs on energy,and that energy ultimately comes from food.the major fuels are simple carbohydrates.after digestion complex carbohydrates,fat,and proteins can be turned into energy sources by conversion to glucose.this largely happens in the lives and skeletal muscles.without fuel on bell can function.after glucose is taken into a cell,it is converted to energy through the action of mittochondria,which are intracellular incinerators generating energy for use in an enormous range of body processes.ye use energy to run all our cellular processes as well as to carry out integrated actions such as muscular movements.the electrical processes in the brain are particularly energy consuming.and a further important use of energy is in the repair and maintainance of our tissues-for example the cells of our skin and of our intestinal lining need constantly to be renewed.

Growth is not possible without the adequate intake of fat,protein,and carbohydrates-the so-called macronutrients,which provide the building blocks for tissue growth as well as the energy that allows cells to divide and multiply.but good nutrition for function and growth must also include micronutrients such as the vitamines and trace minerals.these are essential for specific body functions,often as the catalysts for specific enzyme actions or as components of critical molecules.for example iodine is essential in the body as a component of thyroid hormone.

But fuel supplies must be balanced by their consumption.he people expend less energy than they take in they will gain weight.when excess energy is left on board it is primarily stored as eat under our skin and within our abdomen.he we have a persistently excessive energy intake,fat will also accumulate in our muscles and in the liver.fat stores are a long-term energy supply,just like the camel's hump-an adaptation in that species which evolved for surviving in an environment where there is very intermittent access to done.

Fat has highest energy content for its weight of any body constituent and that is why animals deposit eat under particular situations where having fuel reserves is important.

There have been considerable reductions in our personal energy expenditure since the industrial revolution,although this has been accompanied by a massive increase in the other form of energy consumption through use of electricity and transport fuel.in the developed world the burden of physical labour in the course of work is greatly reduced by machinery.there is a dramatic correlation between motor vehicle ownership and adult obesity in india.

The control of body weight is complex.people have different body weights,not only because they are taller or shorter but because they have stored different amounts of eat.and in the absence of significant changes in habit,our body fat content remains relatively constant-winter or summer,at work or on vacation.tits part of the variation in body composition between individuals appears to be innate;consequently it must have something to do with our individual underlying physiology.it cannot simply be due to differences in supply or demant.

We have seen how species evolved to primarily live within their conform zones.our energy system-that is,the nature of our metabolism including the fuel it burns,how it burns,and what it does with excess fuel,are all the products of our evolutionary history and therefore of the environment we inhabited in prehistory.but our metabolism was designed for environments very different from themse we now inhabit.we need to examine the consequences of this change .

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