Preventing people from walking with iPhones to aid weight loss is flawed due to a nonlinear relationship between walking speed and energy expenditure.

“I've had Public Health people who said to me one person wrote and said well I think if we got people to not walk with their iPhones then they would walk a little faster and then they would expend more energy while they're walking across campus and that will help with weight loss and what do you think and I thought well we're still going to cover the same distance there's a nonlinear relationship between walking speed and energy expenditure and the amount of energy is Trivial and etc etc etc”