When you reduce carbohydrates, you need to replace them with an alternative food type as your energy source. With LCHF this is provided by fats and oils.
Low Carb
High Fat is a slightly misleading name, as
- you will be eating normal fats instead of reduced fat/lite products
- the fat content in an LCHF diet may often just be higher as a proportion of your total carbs/protein/fat ratio due to the reduction in carbs, rather than due to much extra fat being consumed.
And it's worth being aware that:
- there is nothing wrong with full/normal fat foods - they were an essential part of our diets for 100s of years prior to the 1970s, and we survived pretty well on them
- eating fat doesn't make you fat, it's generally a diet high in carbs that does so
- bad cholesterol levels are not necessarily related to dietary cholesterol
- you body is actually designed to use both fats and carbs as its fuel and will (re-)learn how to do so once you've reduced the carbs in your diet to a sensible low enough level to trigger this process again... and so be able to work more efficiently without you getting hungry every five minutes due to needing a carby top up to your fuel tank

I've eaten a low carb normal fat diet for over 3 and a half years, I've lost a fair bit of weight and kept it off, I've reduced my glucose levels from well into the diabetic range down to low pre-diabetic/just about normal and kept them there; I've also come of metformin
and most of my other long term medications, and amongst other things have got rid of long term brain fog and reduced the incidence of food related migraines.... So for me LCHF and scoffing fat has done me much more good than any harm.
Robbity