Losing weight, whether or not you diet, is the result of your body burning more energy than you consume in the form of calories.  If you don't want to diet, then you better pick up the pace and excercise.  There are plenty of web sites out there that tell you how many calories you burn doing different things.  Be prepared, though.  Most often, you are not burning nearly as many calories as you think you are.  That's why it's pretty hard to lose weight without dieting. 

Another thing to remember is that you can diet without dieting.  It's called moderation.  Eat what you want, but if what you want is high in fat or calories or both, eat less of it.  That's what I've done and I've gone from 198 to 140 since February.  I'm 42 years old and female, have had 5 children.  I'm nobody special, but I did it.  It's not as hard as you think.