The Keto Diet is also know as Low Carb High Fat (LCHF). It calls for high fat, moderate protein and low carb. Google will give you lots of information. Just like any diet it has its promoters and opponents.
We follow LCHF in our house b/c my husband does triathlons and he finds that way of eating benefits his athletic performance. Pre-op, I felt better on it because i wasn't eating as much processed crap - kept by carbs under 60 grams. Many on Keto recommend keeping your carbs at 30 - 50 grams. I found that very difficult to maintain. I personally did not see much weigh loss, despite feeling better.
Now that I am post -op, I will resume when this type of plan when I am cleared for solids. While my husband does high fat, moderate protein and low carb, I will do high protein, moderate fat. This will allow us to cook one meal - he can add the extra fat to his serving. The plan is consistent with my NUT recommendations.