How can eating lots of fat and no carbs help you lose weight?

Depends on the fats: A body's metabolism varies person: person and a diet heavy in poly unsat. Oils vis saturated oils differs that fat though oils can become fats. Initially your body is looking for simpler fuels to utilize, and without carbs it is forced to use alternate fuels ie proteins and fats. Fat has a lot more energy release- and once your body is forced to use this fuel, long term- not good.