Obesity is now a critical global issue. More than 2.1 billion people – nearly 30% of the global population – are overweight or obese today (Ng et al. 2014). That’s nearly two and a half times the number of adults and children who are undernourished. Obesity is responsible for about 5% of deaths worldwide. Simon Stevens, chief executive of the National Health Service England, warned in September that “we are sleepwalking into the worst public health emergency for at least three decades.”1