After I went over to low carb higher fat, lots of eggs, olive oil, double cream my bad cholesterol fell to the floor and my blood pressure is lower than it was 40 years ago.
Fat is very calorific which could well help you gain weight, my diet for the past 3 and half months has been LCHF both my Hba1c and cholesterol have fallen, hba1c 52-41 that's for the last 2 month period, my recent cholesterol is down from 6.1 to 3.8 that's compared to 6 months ago.
I use butter, olive and coconut oil, double cream, various cheeses, Avocados all nice and fatty and they've kept me full, if I need extra carbs when I exercise, I add in bananas and berries in to a green smoothie that is laced with coconut oil.
The Cholesterol Conundrum - and Root Cause Solution - YouTube
Sorry, its a long video, but well worth the view. It presents what recent research has discovered about fat and cholesterol. And in answer to your question about weight, then you can use carb control to adjust your bgl, and fat control to gain or lose weight. Simple.