This is an extermemly interesting question. One of the recent pieces of research suggests it is to do with the changes in diet occuring due to migration of people from rural areas to urban. The diet of the countryside is large quantities of carbohydrate with some protein, whereas in cities the diet is much more rich and varied. studies show that people whose metabolism has, in early life, been used to a carb-rich, voluminous diet has difficulty in switching to a more suppliant, low-quantity diet. but people who have been used to a concentrated dense diet all their lives have no problems with it. The body is a versatile system for coping with many kinds of food, but not with sudden changes in diet. it is hoped since r-u migration and urbanisation are on the decline in many parts of the world, that we will se a decline in this problem as people settle down into the current diet. the people who will suffer from obesity are those who have grown up on a thin diet of large quantity, and change to a thick rich diet later in life. say a boy born into a poor family, high aspirations, becomes rich and is able to afford luxurious french gourmet food - he will become obese, with high cholesterol, high blood pressure as a consequence and all the health problems associated with this - strokes heart attacks blood clots diabetes renal failure congestive heart failure pulmonary embolus, the works.

Sorry about the previous response. it was a little unidirectional and probably needs a little background to understand. I was trying to highlight a single, very recent development in our understanding of obesity whereas the subject is much more vast.


Another common problem is the misunderstanding of many people between the connection betweent eating fat and overeating, and obesity. Obesity is a disease for which one of the risk factors is 'bad diet'. There are many other risk factors, equally or more important, for the manifestation of the disease.


In particular, exercise is probably more important than diet. Many ordinary people in the western world are educated enough to know this, primarily by the media i suspect. But the changes in lifestyle which involve a non-physical workforce -- a generation of button-pressers and decline of manual labourers -- implicates mechanisation and computerisation of the last 50 years(in addition to the industrial change's requirement for increasing numbers of desk-based jobs in the previous century) in the aetiology of obesity.


The prevalence of obesity is much affected, as we now know, by genetic factors. There is no single gene for obesity; multiple alleles are involved. The implication of this is that obesity is as much a biochemical disorder than a simple matter of calorific overload. Fat metabolism, for instance, is controlled in a very complex regulatory pathway which, in 'healthy' people are able to cope with any kind of diet. High lipid intake in itself is no problem for the body. Even a diet high in the most badly regarded lipids ('trans fatty acids' and 'saturated fats'- both very large categories of lipid) have little effect on much of the population.

[Obesity is usually diagnosed in terms of body mass index (BMI) = mass/(height squared) ]




A more complex aetiology is suggested by a completely different point of view. An experiment recently used thirty obese subjects (O) and thirty normal controls (C). Each group was divided into two groups of fifteen, R and S. The subjects were told they were coming for some kind of unrelated experiment, and were left (one at a time) in a waiting room in front of a bowl of sweets/crisps, and actors. Subjects R were waiting with relaxed, happy actors, whereas group S were placed with stressed and upset actors who behaved agitated and nervous. The subjects were watched on concealed camera for the thirty minutes' wait, and the number of sweets eaten were analysed.

sweets (average)

CR 7

CS 5

OR 7

OS 14

The results speak for themselves.


The theories now treat obesity as much as a psychological disorder as one of lack-of-knowledge. The obese subjects reacted in an inappropriate way to stress by misdirecting the agitation as hunger or a need for food (whereas normal subjects probably turned their attentions to fidgeting or pacing around). The same rules then apply to obesity as apply to any psychological disease. There are already hundreds of theories of depression, anxiety disorder, and particularly anorexia nervosa and bulimia, which are applicable to obesity (or at least, to certain kinds of obesity).

Some theories would blame maladaptions during childhood for the disease, or attitude abnormalities; others would blame the stressful environment itself; sometimes it is the parents, sometimes it is conditioning, that is the first node of the psychological disease tree.

This fresh approach has suggested many new 'therapies' for obesity as a disease, like cognitive therapy, or learning therapy, exposure therapy or operant conditioning.



But then, is education and planning the ultimate reason for the increase of obesity? Or is it availability of the kinds of food that provoke this psychological 'comfort eating' or such like? One has to ask, with all addictions (for that is what some psychologists treat certain kinds of obesity as), why do we always get addicted to something that is bad for us?

Perhaps, instead of the usual approach, which suggests that 1) too much of a good thing is a bad thing and 2) too much food is now stigmatised as being bad for you, perhaps we should see that 3) stigmatising something as bad for you has psychological taboo-effect and 4) almost all taboo substances, which we know are bad for us, are used in times of stress to comfort us.

There are many explanations for this stress-induced taboo requirement. One is the desire to feel in control of onesself; a need to demonstrate to oneself that one has free will and can still 'indulge' in what is 'not healthy'. This of course was first applied to smoking and drugs: you may know that nicotine-free cigarettes have a marked effect on reducing stress if people think they are getting their nicotine rush! Of course this is partly conditioning, but many say it is the thought that they are 'doing something bad'... In this sense, it is the fact that people know certain foods are 'not good for them' that causes the stress-induced comfort eating. However it should be stressed that, as in the experiment, we the process is largely unconscious, and that I am sure the experiment would not be altered if the food used were changed into salad or something! I personally believe it is the mind's misrecognition of the autonomic signs of agitation as hunger.


Other theories apart, are we to educate more people of the dangers of overeating -- or rather, a diet inappropriate to their lifestyle? there seems to be no harm in binging on huge amounts of fatty chips if you run a few miles every morning.

There are particular dangers, as we find that in addition to the current discussion, there has been a marked increase in the incidence of anorexia nervosa in the last thirty years. There is, similarly, a huge body of evidence suggesting that the media attention to 'excessive eating causing fatness' is a very important cause of anorexia. I think that a problem is that in English, unlike several other languages, the word for dietary lipid and the word for large bellies are the same. The adjective and noun 'fat' should really be quite different senses, but are often conflated in English. 'gros' vs. 'gras' in French, 'gordo' vs. 'grasso' in spanish.

Another popular mistake is belief that being fat, eating fat, being obese, and particularly fat-related disesases is all the same thing. It is very important to realise that all the thrombotic and embolic vascular diseases that people associate with baing fat are due to cholesterol - a chemical carefully regulated in the normal human, and although this chemical is regulatable by diet, there are in most cases of hypercholesterolaemia, distinct metabolic abnormalities. It, too, is highly genetic. And although cholesterol is actually classified as a lipid (in the common parlance, a fat), it bears little resemblance to most fats and is NOT present in the 'fat' seen in peoples' bellies. It has nothing to do with being fat per se, although it is found in many of the foods that do also contain the nasty fattening fats (i.e. red meat & butter/cheese). The link that does exist with obesity and cholesterol, therefore, is evidence for the diet-based causation of obesity.


Now, education has been suggested to help people understand what to eat. This is indeed a good idea, but the issue is in fact so complicated, that it would be nonsense to simplify it to a level at which people would understand why they should sometimes eat certain things and not others. The previous e-mail should certainly serve to show the added complications included by recent research -- that is, how metabolic conditioning from childhood affects the biochemistry of the blood in such ways as to cause obesity under certain changes of diet throughout life, and that children brought up on high energy or 'fatty' diets have no problems in coping with them.

No ordinary human will want to be taught the intricacies of lipid metabolism, nor certainly the statistics on diet, genetics and psychology. How do we come up with reasonable ideas for dietary control in a society? It is impossible to control culture without the expenditure of vast resources. And indeed, food is culture. You would really have to go about changing culture to change the way people regard and choose their food.

We have been eating for far longer than culture ever existed, and inevitably culture itself is inextricable from the food we eat. It is one of the few major things, along with sex+marriage, religion, clothing, manners+customs, and education, that define a culture as being different from another. Which is bound to be the case since we eat every day, often several times a day, and do it all our lives. The number of metaphors and idioms that involve food is incredible, more than the weather or dress or tools. The force of food is an incredible one, but we really need to explain that old phrase, 'you are what you eat', a little more clearly, if we are to obtain a sensible and medically theraputic diet.