The question is why is leg fat so hard to lose. When assessing body fat it is important to remember that we all hold body fat in different areas. Some people hold more body fat in their stomach some may hold more body fat in their arms and some may hold more body fat in your legs. For the most part, body fat distribution is going to be mainly genetic. So what can you do about it?
If you tend to hold more your body fat in your legs you can obviously do leg training to try to tighten up the muscle. However it has been said that the human body cannot quote-unquote spot reduce. What that means is you can just say, Okay I want to lose body fat on my legs and train your legs to lose body fat. To lose body fat you need to burn more calories than you take in and try to lose weight overall. How your body fat loss is distributed for the most part is going to be genetic.