The causes of obesity: an in-depth review

Obesity is a medical condition defined as disproportionate fat storage in the body that might adversely affect health.1 The prevalence of obesity is drastically rising globally, and it is now considered a critical public health issue. According to the World Health Organisation WHO (2016), there are just under 2 billion overweight adults in the world. More than 600 million of them are considered obese. Around 40% of adults were overweight in 2016 and just under 15% were obese. The global prevalence of obesity has increased by threefold between 1975 and 2016. If the trend continues to rise, it is estimated that close to one third of the world adult population will be overweight and more than1 billion will be obese by 2025. Obesity is measured using body mass index (BMI) which is calculated by dividing the subject’s weight in kilograms by their square height in metres.1 A BMI of 30 or higher indicates obesity and although BMI is a very useful initial assessment method to diagnose obesity, it is not particularly accurate. It does not always reflect the degree of individual’s fat storage with great certainty. The WHO recognises this limitation and recommends its use as a screening tool only. Obesity infers a huge economic burden on the already outstretched health systems in many countries. The economic cost of obesity in England has been anticipated at being between £3.3–3.7 billion with an additional £3-3.7 billion related cost to treating overweight individuals.2