Overweight and obesity are severe public health issues with rapidly increasing rates in developed as well as developing countries. According to the World Health Organization, 1.9 billion adults (over the age of 18) were overweight in 2014, and 600 million were obese. In addition, 42 million children under five were overweight or obese in 2013. For policies to be successful, a solid understanding of the causes of weight problems and appropriate indicators are needed. At individual level this implies for instance to look beyond the calorie balance concept and consider the functioning of the complex biological system that regulates body weight as a whole. Furthermore, systemic factors like the implications that the current food system has for consumption behaviour, should be taken into account.