We all know that losing weight is difficult - and keeping it off is even harder. And now one leading scientist has a compelling theory about just why that is. Professor Lewis Halsey tells Harry Bullmore why ‘energy compensation’ is partly to blame M any people want to lose weight; few successfully do. Research also shows that those who are able to lose fat often gain this weight back over time. Yet weight loss is frequently presented as a simple and easy concept: to see the number on the scale