Nearly one-third of the world’s population is obese or overweight. The number is approximately 2.1 billion people. This is nearly 30% of the world’s population! In developed and developing countries, the rise of obesity, over the past 3 decades, has been rapid, substantial and widespread. Obesity is a bane to our modern world. The causes of obesity are complex. There are many interrelated factors, such as genetics, lifestyle and how your body uses energy.