In the New Testament, Christians were only told to abstain from eating blood and meats offered to idols. There is nothing wrong with eating pork; however, since pigs do carry a lot of diseases, their meat has to be very thoroughly cooked (like chicken).
God has changed the rules for eating in different eras. For instance, before the Flood, people were supposed to eat plants only and meat was forbidden completely. (What the Bible calls meat simply meant food in general, whereas what we call meat today refers to the flesh of animals.)
After the Flood, God told Noah that he could now eat all things. (Genesis 9:3 Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things.)
When God gave the law to Moses, only clean animals were allowed to be eaten (swine were considered unclean). Now, however, we can eat pretty much anything we want as long as we are not gluttonous and try to do what is healthy for our own bodies. Since each body is different, not everyone will react the same to any specific diet. So, if a Keto diet makes you feel healthy, then I see nothing wrong with doing it.
