The idea behind creating warm clothing is layering your clothes to create thermal air pockets in each layer thus keeping you warmer. A t-shirt under a really thick body warmer is hopeless.
That's why you can be assured that if you layer up with MAD clothing you'll stay warmer longer. Combine a MAD T, MAD HOODY and one of these superb MAD bodywarmers and you'll beat the freeze whilst staying mobile.