Why would I feel sluggish? This makes zero sense.
1. Eating fat doesn't make you feel sluggish.
2. 30% fat by calories is a relatively LOW fat diet.
Have you ever tracked everything you eat? Weighed everything, added up every gram of every single thing? You might be surprised at what you are actually eating.
When people start eating 20% or less calories from fat, they generally have all sorts of issues, like dry skin, rapid metabolism of meals, etc.
Fat is ENERGY, when you take your fat too low, you have to take your carbs higher, these carbs then digest faster (because of the lack of fat), this means higher insulin response and faster digestion which leads to being hungry faster.
Honestly, this sounds like you have been affected by the anti-fat propaganda that came out of the 80s and 90s. There is no direct connection between DIETARY fat and BODY fat, they are completely different, lower fat/higher carb diets generally lead to more body fat.
Finally, fatty acids are on of the most important parts of your diet.
If you think, well then, I'll eat low fat AND low carb, then you are just going to turn all that protein you have to eat into glucose, this isn't ideal either.