So back to Causes.
Among other factors, rising incidence of obesity in the UK can be explained by behavioral theories relating to changes in physical activity and eating behavior.
Basic weight gain is most commonly caused by excess energy consumption for expenditure. Rising incidence of overweight and obesity on a population level, however, is more complex. Whilst there are individual physiological and genetic factors resulting in obesity, one may infer that obesity trends are a result of multiple direct and indirect factors including social, political and economic factors affecting our behaviour. Some of them are introduced here.
Environmental factors of societal and market forces driving eating behavior within the population are an area of increasing interest. An obesogenic environment is one where the food and activity environment may drive individuals towards obesity progression. Plenty can be said about obseogenic environments and I will write about this particular aspect more pointedly in future.
Physical Activity and Inactivity
Similarly, It is well understood that appropriate physical activity is a means of effective weight management. It has been argued that the cause of weight gain pertaining to physical exercise is not only low levels of physical activity, but also by high levels of physical inactivity. Sedentary behaviour in itself is linked to co-morbidities.
One theory for increased incidence of obesity considers decreased levels of energy expenditure. An example of this is a change in shopping behavior. Greater accessibility and affordability of services such as online grocery shopping and delivery positively impact the lives of many people, e.g. disabled and elderly, but many modern conveniences have come at a social cost to health.
A greater proportion of the working population in the UK is employed in occupations conducive to levels of relative inactivity. Improved transport services, urbanization, affordability of vehicles and even mobile internet access have made life more convenient, de-necessitating much of our passive physical activity. As early as 1984, a US telephone company estimated that an additional phone extension in the household saves approximately 1.6km of walking annually.
It has been found that children were more likely to be obese for each additional hour of sedentary time. Low levels of activity have been shown to be the most prominent risk factor for weight gain. This trend of increased sedentary behavior may form part of the forces driving obesity incidence in the UK.
Genetics & Physiology
A number of studies have explored the genetic bases of obesity. In particular, twin studies and Genome-wide association studies (GWAS). Results of the Twins Early Development Study (TEDS) show a strong heritability of adiposity and waist circumference as do GWAS. However, these explain less than 3% of BMI variation in children and adults.
Furthermore, it is unlikely that genetic factors are central to rising obesity incidence, as these have not changed substantially, relative to the short time frame of rising prevalence discussed earlier.
There is no doubt that the causes of rising obesity are complex, multiple and multifactorial. Thus, this article has a Part 2: More Causes of Rising Incidence of Obesity in the United Kingdom