SERIES: Part 2 – Causes of Rising Incidence of Obesity in the United Kingdom

This is Part 2 of my Obesity in the UK series. If you missed Part 1, you can find it here.

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 Obesogenicity

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.

Eating Behaviour

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

SERIES: Rising incidence of obesity in the United Kingdom – Introduction

In the past three decades obesity in the United Kingdom has increased three-fold, emerging as one of the UK’s most prominent public health challenges. Obesity is largely a lifestyle and behavior associated condition, although there are also some genetic factors.

Obesity is measured by a standard anthropometric measurement of known as Body Mass Index (BMI). The terms overweight and obese are usually classified as increased weight-for-height. The figure below classifies the BMI ranges used to define BMI status. (Do you know your BMI?) BMI is calculated by dividing the weight in kilograms by the square of the height in meters. (Or googled)


An individual whose weight is two or more times the ideal weight is classified as morbidly obese.

Recent studies show steady increases in obesity incidence both nationally and internationally. Indeed, today we live in a world where more people are clinically obese than those suffering morbidity or mortality due to starvation.

Globally, the percentage of people classified as overweight or obese increased in both men and women from 28.8% and 29.8% in 1980 to 36.9% and 38.0% respectively. Child overweight and obesity also increased. In 2013, World Health Organization adopted a target of halting the rise in child obesity by 2025.

The primary reason obesity is a public health concern is because it is a risk factor for other non-communicable diseases (NCDs) such as Type II Diabetes Mellitus (T2DM), hypertension and coronary heart disease (CHD). Morbid obesity, considered the most serious stage of obesity, can leave patients at the highest risk of mortality related to their obese status.


Throughout this series I will outline the causes and consequences of rising obesity incidence as identified in empirical studies and literature. All sources are available upon request.

Likely due to methodological challenges, much of the available data on obesity in the UK and elsewhere discuss prevalence and not necessarily incidence. However, understanding disease prevalence and its nuances is useful in interpreting both causal and consequential factors of incidence.

 According to Health Survey for England (HSE), in 2013, 26% of men and 24% of women were classified as obese; 41% of men and 33% of women were classified as overweight. Scotland and Wales had similar findings.

The UK has seen increases in obesity in children for several years. In 1995, 11% of boys and 12% of girls were classified as obese. By 2005, these numbers were 18% and 19% respectively. These increases have since leveled off: to 16% of boys and 15% of girls in 2013.

The prevalence of obesity is significantly higher in some groups. Children were more likely to be obese if they lived in an urban area. Whilst 22% of boys and 21% of girls from the lowest-income families were already obese.

Rising incidence of obesity is a problem

The major problem presented is the co-morbidities with which obesity is associated. Obesity is a major risk factor for many NCDs, thus causing and contributing to a high proportion of morbidity and mortality.

Type 2 Diabetes Mellitus (T2DM) is strongly correlated with obesity. The detrimental effects on an individual living with obesity and T2DM are multiple-fold. Rising incidence of obesity in children is well correlated with incidence of childhood T2DM. Expectedly, in terms of reducing the risk of cardiovascular diseases, particularly coronary heart disease, greater reduction in adiposity results in greater risk reduction. With the exception of LDL cholesterol, fat loss in obese patients improves blood pressure, glycemic control and lipids.

T2DM is simply hyperglycemia resulting primarily from a resistance to insulin but also from impaired insulin secretion. Clinical studies have shown the metabolic effects of high sugar, particularly fructose. These sugars mediate fatty liver and insulin resistance in humans. In a typical Western diet, the majority of fructose comes from sugary, soft and fruit drinks, often resulting in significantly elevated levels of fasting glucose and thus, high levels of insulin, leading to resistance.

Obesity also has a role in worsening nocturnal hypoxia in obstructive sleep apnea syndrome (OSAS). It has been theorized that oxidative stress and inflammation caused by OSAS is a major factor causing cardiovascular morbidity and mortality in obese patients.

This series will explore the causes, consequences and some potential solutions to rising obesity incidence in the UK. The significant contribution of behavioural factors to the rising prevalence and incidence of obesity suggests an important role for well-defined interventions to manage and reduce obesity levels. It is clear, however, that the burden and cost of the consequences of obesity justify the need for the United Kingdom to aspire to meet its own targets and those set by the World Health Assembly.