Clarification: I didn’t say you had to set carbs at or below a certain level. I said a high fat diet will need less carbs, for obvious caloric reasons (see more explanation below). If the increase of fat is new, then I suggest trying out 2 weeks at your current calorie level, but switch to the higher fat level. I think it’s best to see for yourself how just switching to a higher fat diet, while holding cals constant, effects you. Fat gain can be expected if fats increase drastically while in a caloric surplus.
Discussion: I have eaten this way for cutting and occasionally (and plan to very soon) for normal caloric phases (to maintain/increase lean mass for a sport that requires weight restrictions). When on a cutting diet it works well for me and I can lower carbs and keep muscle and have energy (as long as carbs are 100-200 depending on average daily activity level – more carbs when more workouts, even on non-workout days if I feel I need them, which I read as a sign that I am doing it right. I believe that the reason for this is increased insulin sensitivity when carbs fluctuate/teeter on the verge of being adequate/slightly-inadequate for normal glucose replenishment. Transitioning to higher fat diet (lower, but not “low” carb, i.e. not ketogenic – where carbs are in the range of 100-200g/day) will also increase the body’s creating it’s own glucose from adipose tissue, IF AND ONLY IF total cals and carbs are in check. This is a good thing as excess carbs tend turn to fat.
Cutting/Normal Carbs: My experiences from this type of dietary strategy was positive. I speculate that it will work well for situations with “normal” calorie levels.
Bulking: If you are bulking, then high cal plus fat is a bad idea. Moderate fat with adequate amounts of each fatty acid (3,6, 9, saturates, etc) and variable carbohydrates (day 1 or 2 high, day 2 or 3 lower carbs). Cardio and supplements help to modulate this effect as well.