Recenly I passed on a press release from a study to Ren's blog.  It was on the role of Calorie density and Weight loss. 

Foods with high water content can be a great way to eat, avoid calories and feel satisfied.  For example we could eat 6 medium apples at 60 calories each or 1 cheeseburger at 380 calories (source: Nutritiondata.com), which is more satisfiying, filling and healthier.  Simple choices can go a long way to achieving weight loss.

Even though train for road races and triathlons and in the winter 50km XC loppets, I still concioiusly avoid the lure of the high fat, high calorie foods.  I have found that it takes between 1-2 months to establish a habit (ie. not notice less sugar in your tea, doing daily walks, avoding the favourite fast food), once after that withdrawal period it becomes part of you.

BTW I just posted in pets about Canine Obesity and the Further Reading gives some of the benefits for humans and animals regarding calorie reduction