A very comprehensive collection of statistics tells us that the incidence of some very common diseases is even more common in individuals who are either overweight or suffer from obesity.
Clearly with each of these diseases there are individual factors acting to both initiate and exacerbate the particular condition. Some of these factors are easy to identify. So, as an example we know conclusively that smoking causes lung cancer to the extent that more than 95% of cases of lung cancer arise in smokers. In the small number of non-smokers who develop lung cancer it is obviously more difficult to identify a cause and it may be that passive smoking is a contributor or alternatively another cause altogether which is yet to be identified.
Equally with osteoarthritis we know that this is a degenerative change in the major joints of the body in particularly the hip, knee and shoulder as a result of excessive wear and tear and injury. In the latter case, it is relatively straight forward to draw an association between obesity and the increased risk of osteoarthritis simply because if the individual is carrying around more weight then there is going to be more wear and tear on the joints.
However, with some diseases in particular many of the common cancers such as bowel cancer and breast cancer, whilst we have identified certain factors that might be responsible for causing the disease, in many individuals these particular causes cannot necessarily be identified or confirmed. It is therefore equally difficult to draw a relationship between obesity and these diseases, despite the fact that we recognise that they are more common in this particular group.
As far as the individual diseases are concerned there is a presentation on each of them and where the information is available, such as with osteoarthritis then we identify the putative link between obesity and the aetiological factor itself. However, when we are less clear as to what causes the condition in the first place, we make no attempt to draw any conclusions as to how obesity may exacerbate these initiating factors.
An enormous amount of research is currently being done with most of these diseases and all we can wish for is that at some point in the future these factors will be identified. In the meantime, we are duty bound as individuals and as a society to try and reduce the incidences of these common diseases. And where we know that obesity is itself a risk factor, whilst not knowing the exact mechanism, we are nevertheless duty bound to manage people who are in the overweight category and to treat those who are suffering from obesity in order to reduce their individual risks.