The dietary laws in Leviticus 11 were for the Jews only. Over and over you will see the phrase "unclean unto you". These foods were not necessarily bad for everyone, but they were unclean for the Jew. And it is summed up at the end. It was to sanctify them and make them a separate people.
Lev 11:2 Speak unto the children of Israel, saying, These are the beasts which ye shall eat among all the beasts that are on the earth.
These commands were not for everyone, just the children of Israel. Some foods were clean to them, and some were unclean to them.
Lev 11:3 Whatsoever parteth the hoof, and is clovenfooted, and cheweth the cud, among the beasts, that shall ye eat.
4 Nevertheless these shall ye not eat of them that chew the cud, or of them that divide the hoof: as the camel, because he cheweth the cud, but divideth not the hoof; he is unclean unto you.
So again, some of these foods were not necessarily unhealthy, but for the Jew they were unclean. And you will see that phrase "unclean unto you" over and over in this chapter.
And at the end it tells why.
Lev 11:44 For I am the LORD your God: ye shall therefore sanctify yourselves, and ye shall be holy; for I am holy: neither shall ye defile yourselves with any manner of creeping thing that creepeth upon the earth.
45 For I am the LORD that bringeth you up out of the land of Egypt, to be your God: ye shall therefore be holy, for I am holy.
46 This is the law of the beasts, and of the fowl, and of every living creature that moveth in the waters, and of every creature that creepeth upon the earth:
47 To make a difference between the unclean and the clean, and between the beast that may be eaten and the beast that may not be eaten.
In the New Testament, as believers were are told to turn from sins. Anybody who thinks they have a free pass to sin as a Christian is wrong.
2 Cor 6:1 We then, as workers together with him, beseech you also that ye receive not the grace of God in vain.
2 (For he saith, I have heard thee in a time accepted, and in the day of salvation have I succoured thee: behold, now is the accepted time; behold, now is the day of salvation.)
3 Giving no offence in any thing, that the ministry be not blamed:
4 But in all things approving ourselves as the ministers of God, in much patience, in afflictions, in necessities, in distresses,
5 In stripes, in imprisonments, in tumults, in labours, in watchings, in fastings;
6 By pureness, by knowledge, by longsuffering, by kindness, by the Holy Ghost, by love unfeigned,
7 By the word of truth, by the power of God, by the armour of righteousness on the right hand and on the left,
8 By honour and dishonour, by evil report and good report: as deceivers, and yet true;
9 As unknown, and yet well known; as dying, and, behold, we live; as chastened, and not killed;
10 As sorrowful, yet alway rejoicing; as poor, yet making many rich; as having nothing, and yet possessing all things.
2 Cor 6:14 Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?
15 And what concord hath Christ with Belial? or what part hath he that believeth with an infidel?
16 And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people.
17 Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you,
18 And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty.
We are supposed to be different from the world, just as the Jews were to be different from the nations around them. They had dietary laws, laws concerning how they dressed, and even how they could cut their hair, or body markings such as tattoos. This was to make them identifiable and separate from the nations around them.
And today as Christians were are supposed to live holy lives and turn from all the sins around us. People should be able to identify us by our behaviour and conduct.