Show them don't tell them. If you say it it's an opinion, if they say it its a fact. Information is great but people are rarely sold on just the facts. Best advice is to go along your paleo way and get super healthy. The time will come when someone will stop and ask what your doing. At that point and only at that point can you help someone.
In this case it's not really about Paleo but rather a long standing sibling rivalry. Here's some advice from Og Mandino that might apply:
By Og Mandino
Why do so many people let their dreams die unlived? I suppose it is the negative, cynical attitudes of other people. These other people are not enemies; they are friends, even family members. Our enemies never bother us greatly; we can usually handle them with little trouble. But our friends, if they are nay-sayers, are constantly punching holes in our dreams with a cynical smile here, a put-down there, a constant stream of negative vibrations- our friends can kill us! A man gets excited about the possibility of a new job. He sees the opportunity to make more money, do more meaningful work, rise to a personal challenge; the old heart starts pounding, and the juices begin to flow, and he feels himself revving up for this stimulating new project. But then he tells his neighbor about it over the back fence one evening. He gets a smirk, a laugh that says, "You can't do that", a foot-long list of all the problems and obstacles and 50 reasons why he will never make it and is better off to stay where he is.
Before He knows it, his enthusiasm falls down to near zero. He goes back into the house like a whipped pup with his tail dragging along the ground. All the fire and self -confidence is gone and he begins to second-guess himself. Now he is thinking of all the reasons that he can't make it instead of the reasons that he can. He lets one five-minute spiel of negativity of ridicule or just plain disbelief from a dream-nothing neighbor; take the steam right out of his engine. Friends like that can do more damage than a dozen enemies can.
Of course, all of us have dreams of a better life in providing more of the good things for those we love and those who depend on us. The trouble is that most of us live in fear, fear that we might stumble and fall if we dare take a chance.
Give it a chance to happen. Don't let your brother-in-law or your plumber or your husband's fishing buddy or the guy in the next office robs you of that faith in yourself that makes things happen. Don't let the guys, who lie on the couch and watch television every night, tell you how futile life is. If you have the flame of a dream down inside you somewhere, be thankful for it, and do something about it. And don't let anyone else blow it out.
Once you select a goal that is really important to you and make a decision to pursue it, the next step is to make up your mind before you set out toward it. You know that is going to require lots of hard work and accept it. You making up your mind before you start that sacrifice is part of the package.
Is this the real secret? Can it be that we all usually go into a new and challenging job or enterprise expecting things to work easily and smoothly instead of planning, up front, for the adversities that are certain to come?
If I could wish for any person in the United States a single quality to secure for him success in life, I would not grant to him in massive intellect or a well-coordinated athletic body. I would not bless him with a physical attractiveness or talent. I would wish for him the ability and the will to persist toward whatever his goal!