Thin is cold.
More than half of the calories we burn are spent to regulate our internal temperature according to Pierre Dukan, the author of the Dukan Diet. And being cold will increase that number dramatically...Just by showering in cool water, for example (77F or 25C)you will burn 100 calories every 2 minutes! That's more than ANY cardio workout can do for you!
So, suck on ice cubes, drink ICE cold water, turn down the temperature, roll down the window when it's chilly out rather than turn on the heat in the car! And whatever you do... don't bundle up just because it's a little nippy. Of course, don't risk your health for the extra calories... but if it's in the 50s or 60s, you probably don't need a coat that bad.
Moral of the story: Shiver to burn.