Causes of Obesity

Obesity occurs when energy intake from food and drink consumption is greater than energy expenditure through the body’s metabolism and physical activity over a prolonged period, resulting in the accumulation of excess body fat. However there are many complex behavioural and societal factors that combine to contribute to the causes of obesity. The Foresight report (2007) referred to a “complex web of societal and biological factors that have, in recent decades, exposed our inherent human vulnerability to weight gain”. The report presented an obesity system map with energy balance at its centre. Around this, over 100 variables directly or indirectly influence energy balance (Figure 1).

The Foresight map has been divided into 7 cross-cutting predominant themes (Figure 2):

  • Biology: an individuals starting point - the influence of genetics and ill health;
  • Activity environment: the influence of the environment on an individual’s activity behaviour, for example a decision to cycle to work may be influenced by road safety, air pollution or provision of a cycle shelter and showers;
  • Physical Activity: the type, frequency and intensity of activities an individual carries out, such as cycling vigorously to work every day;
  • Societal influences: the impact of society, for example the influence of the media, education, peer pressure or culture;
  • Individual psychology: for example a person’s individual psychological drive for particular foods and consumption patterns, or physical activity patterns or preferences;
  • Food environment: the influence of the food environment on an individual’s food choices, for example a decision to eat more fruit and vegetables may be influenced by the availability and quality of fruit and vegetables near home;
  • Food consumption: the quality, quantity (portion sizes) and frequency (snacking patterns) of an individual’s diet.

Figure 1

'Full obesity system map'

Figure 2