The ketogenic diet defines the proportions of fats, protein and carbohydrate - but does it matter which fats, protein or carbohydrate we use?

It is likely that all aspects of our behaviour are far more determined by our genetic makeup than most people realise, and that we are not so different to the rest of the animal kingdom as most people would like to believe.

Now the whole period of time that man has been civilised is very short in genetic terms, and certainly not long enough to cause much change to our genetic make up. That means we operate in a civilised society with a genetic behaviour designed for a very different environment - civilisation is literally a veneer, and many of the problems in society may be caused by conflicts between our underlying genetic behaviour and what is now expected of us.

In the case of diet, our genetic make up says that we were scavengers, eating whatever we could get, from second hand meat to roots to honey. Since we were successful and colonised most of the world, we were able to use a very wide variety of food sources, and live on many different balances of diet. We were also capable of operating with variable food levels from periods of near starvation to great guzzling blow outs. So, on the whole, we should not have to be very prescriptive about diet. Our metabolic engine was designed to run on a very wide variety of fuels, and we should be able to eat pretty well what ever we like without too much difficulty. In particular, anything which is essential to our survival (like vitamins, or carnitine, or essential fatty acids) should be readily available in a wide variety of foods. But, we should beware of the gross changes in dietary behaviour to which our genetic system will not be adapted. There are at least three such changes:

• Food is far more readily available, and there is the risk that we just eat too much.

• Many of the things we ingest with food are man made chemicals that do not exist in nature, and which our genetic system is not designed to cope with. There is therefore the risk that some of these could be positively harmful.

• Food is infinitely more hygienic, which probably means that we are denying our immune systems the inputs that are necessary to build the proper protection against disease.

Based on this, a general philosophy for diet would be:

Eat what you like, but make the diet varied, and do not eat too much. Eat natural foods where practicable, but don't make a religion of it. And, a little bit of dirt won't hurt; cleanliness is only next to godliness because you will die faster.

Now, the ketogenic diet is a bit different. Because it is so extreme, there is a risk that we will miss some essential dietary element. So it is very important to make the diet as varied as possible, in order to reduce this risk. The other aspect is the question of fat. Because fat is such a major component of the diet, it needs special consideration. However, there are two problems:

• The metabolism of fat is not very well understood, and much of what is currently said about fats does not have a solid scientific basis. - it is not inconceivable that the idea that essential fatty acids are good for you is just as erroneous as the idea that cholesterol is bad for you.

• The role of fats, and particularly different sorts of fat, in the ketogenic diet is not understood at all. It may be that the presence of some particular fat is crucial to the success of the diet. It could also be that the presence of a particular fat (eg a trans-fat) could block the operation of the diet.

Under these circumstances, the best thing would seem to be to use as varied a range of fats as possible, avoiding hydrogenated fats and being very careful when using essential fatty acids that these are not contaminated by trans- fatty acids.

return to   Understanding the ketogenic diet

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(update 2.2: 18 July 2002)
(issue 2: 19 February 1998)