Just my 2c worth. If you are on steroids like prednesalone, then a low carb diet is a smart option. Your pancreas is dealing with the job of responding to food and it's also dealing with the spiking effect of the steroid and a higher required output of insulin that is needed to keep levels down. This is a lot of work. I'd of hoped your doctor warned you about type 2 risk when taking these steroids?
The job of the pancreas becomes so much greater when starch or sugary foods are eaten along with a steroid. Has a dramatic effect on levels and insulin and not in a good way.
If you are a naturally lean person and always have been, then I'd try for a higher protein content more so then fat, eat your fats, but adding more protein to the diet would probably be more beneficial if you are a lean person. Lean people don't have the fat storage capability compared to people who do and gain weight easily. So, I just don't see a great deal of sense in focusing on eating a lot of fat if your body cannot store it. Steroids can cause muscle loss and weakness, so eating more protein I think is a way of counteracting that. This doesn't mean eat a low fat diet by any means, but protein will spare muscle loss and add weight if you eat enough. How much you need fluctuates from one person to the next, so testing levels in response to what you eat helps. Some activity helps, walking for example. I think the worst thing a person taking steroids can do is eat a meal and then sit for an hr or two, not avoidable sometimes, (work, weather or whatever)but even minor activity helps. Resistance training, weights, weight baring exercises etc do also help and I think are essential in preventing muscle loss.
Just my thoughts from someone who has taken steroids for a long period of time.