The fastest way to lose weight is with diet and by running in a suit that prevents your heat to go out.
What happens is that your body heat goes up and you start to use more energy to cool off. (scuba suit is also ok)
However you need to drink a loot of water and watch out for your body temperature (it should not go over 40*C).
If you can keep it on a sick lvl (like the time you need to get rid of viruses) its the best.
You can also use sauna. But its slower.
Generaly you will lose your fat energy, while stil getting enogh for a day.
Just doing diet is a very slow and anoying process.