I'm writing this one on the fly, so here goes! How does this sound as an advertisement for Christianity: Get saved and lose weight! I imagine in our appearance-obscessed society, if Christianity were advertised like this, people would flock into the kingdom!
Joking aside, there is something to be said for the idea that we who have placed our faith in Jesus Christ will one day received glorified bodies fashioned according to the pattern of Christ's resurrected glorified body (Phillippians 3:20-21). This is part of the "hope of the gospel" that is often overlooked in Christian preaching today. Much of the modern day gospel is focused on what Jesus can do for us in this life.
I don't know about you, but I am rather glad that I am not now what I will be in the future. Here is what the Apostle John has to say on the matter, "Beloved now are we the sons of God. Yet it has not appeared what we shall be. But we know that when He appears, we shall be like Him for we shall see Him as He is." (I John 3:3) Thank God! There are some who would say that heaven is simply an extention of who we are while we are here on earth. They say that "death is not a meanns of sanctification." Perhaps that is true. I am sure that we do not lose our personalites and our self-awareness when we step out into the next life. But if we say that our final state of being is solely determined by our spiritual progress here on earth, we are missing out on a key aspect of the gospel, which says that one day we will be given glorified bodies that will no longer be subject to our current fleshly desires that tend to lead us toward a sinful lifestyle. As the Apostle Paul says, the great mystery of the faith is, "Christ in you the hope of glory." (Colossians 1:27)
Hope that is seen is not hope. So relax. If you need to lose those extra 50 pounds and quit those addictive habits that are constantly getting you into trouble, get saved. Whether in this life or the next, it will happen one way or another.