In the linked study (doi:10.1136/bmj.a2002), Maruyama and colleagues show a significant positive association between two eating behaviours (eating until full and eating quickly) and overweight in a large sample of Japanese adults.1 The study builds on evidence that eating behaviours are important in promoting positive energy balance (taking in more energy than is expended) and may contribute to the current epidemic of obesity. The drive to overconsume energy when it is available is probably an evolutionary imperative; however, until the last decade or so most adults did not have the opportunity to take in enough energy to enable fat to be stored.

The ideal situation whereby our eating behaviours are controlled by biological regulatory systems that tightly regulate appetite and consumption and keep our weight in check—is being challenged. We do not know what drives us to …