^^^^This. Most people don't eat enough fiber in the "normal" (i.e., Standard American) diet, and folks on a ketogenic diet often end-up eating even less. What's more, most of the high-fat/moderate-protein foods -- dairy, in the main... cheese -- tend to gum-up the works, and are calorie-dense; we eat more of them, and get way more calories than we realize, or than we burn. I'm not a CICOpath (Calories-In, Calories-Out), but...

Wheat bran is very good -- a 1/4-cup is only 50kcal, with 6gr of fiber and only 10gr of carbs... it's easy to take in, and it keeps things moving freely (do remember to increase your fluid intake, as well).