300 kcals extra a day is apparently all that is causing most people to be overweight. The weight goes on gradually and means a stone and a half or so of weight is gained over a year or two. Very sobering! It's so easy to eat 300 kcals extra, just a banana and large coffee on top of your daily calorie allowance pretty much, or a piece of toast and a piece of cheese etc. I found this a really helpful stat because it means that if you just don't give into temptation a couple of times a day and start jogging or having a 45 minute walk every day and also decrease portion sizes bringing your daily calories to 200-300 under the allowance instead you would probably lose a couple of stone over a year or so. I definitely underestimate what I eat in a day unless I log it. Hope that might be helpful to someone else too!