There are of course numerous theories being put forward for the increase in the rate of obesity in the US and the UK over the past twenty-five years but, whatever the reason, most observers agree that the following factors all play a part: Insufficient activity.
Both in terms of employment and recreation people are far less active than they once were with far fewer people engaged in manual work and an increasing number of people choosing to pursue relatively sedentary recreational activities.
It is also interesting to note that obese people tend to be less active but that this does not stem directly from their obesity.
In general weight gain (or loss) does not affect an individual's level of activity but a change in activity does produce a gain (or loss) in weight.
A reduction in the cost of food.
The relative cost of food today is lower in the US and much of Europe than at any time in history and the majority of people in both the US and the UK are able to eat more or less as much food as they want.
The low cost of motoring.
Two and even three car families are commonplace today and more and more people are taking to their cars even for the shortest of journeys in preference to using public transport or walking.
Changing work patterns.
In addition to the lower activity in many forms of employment as more of us sit behind a desk or at a computer, it is also increasingly common for both partners to work rather than for one partner to look after the home and take care of cooking the meals.
This, in turn, results in a rise in the number of people eating out at restaurants or buying take-out meals on the way home.
The rise in the popularity of fast food restaurants.
The increasing popularity of fast food restaurants has given rise to intense competition which has, in turn, led to increased portion sizes.
A regular order of fries at McDonalds used to be around 200 calories but today is up around 600 calories.
Increased food production.
Although perhaps not quite such an obvious cause the fact that US now produces about three times as much food as the country needs also adds to the problem of obesity, principally by further reducing the cost of many staple food items to the food producers.
An ageing population.
As we age our metabolism slows and we require fewer calories to meet our daily needs.
Eating habits however do not generally recognize this fact and so obesity tends to become an increasing problem with age for an individual.
However, where a population as whole is ageing, as is the case in the US and the UK, obesity also increases across that population.
One interesting and apparent anomaly in the environmental factors aiding the growth of obesity would seem to be the craze for dieting and exercise which has swept across both the US and the UK.
In fact this is in itself also adding to the problem as studies have clearly shown that the vast majority of diets do not work and invariably people actually gain weight once they come off a diet.
Dieting however becomes something of an obsession for many people and they diet almost as frequently as they change their underwear, creating a pattern of falling and rising weight which, over time, results in a gradual rise in weight.
The net result of the rise in obesity on both sides of the pond is a corresponding increase in the number of people abandoning the diet and exercise routine and opting for the gastric bypass as the solution to their problem.
While this is not an easy option it is certainly an effective one.