Ok. I'm going on a little rant here. The verse referenced here is I Samuel 16:7 . . .
. . . for the Lord seeth not as man seeth; for man looketh on the outward appearance, but the Lord looketh on the heart.
If there were a contest for Verses Most Often Taken Out of Context, I believe this one would win, or at least place in the Top Ten.
I have heard this verse quoted probably hundreds of times in my life, and rarely have I heard it used in the same way that God used it when he was talking to Samuel. In this passage, Samuel has been sent by God to Jesse's house to anoint the new king of Israel. When Samuel gets there, he finds that Jesse has eight sons, and when he saw the firstborn, Eliab, Samuel said, "Surely the Lord's anointed is before him." He just knew that this must be the intended king, because he looked so good, but God said no. Don't look on his height or his good looks, because "the Lord seeth not as man seeth; for man looketh on the outward appearance, but the Lord looketh on the heart." Samuel went through all the sons of Jesse, but not one of them was the Lord's intended for Israel. Finally, Samuel asks if there are any more sons, and Jesse says there's just the youngest left, and he's out tending the sheep. Samuel says go get him - we won't sit down till he comes. When David got there, Samuel had a surprise - David was ruddy, had a beautiful countenance, and goodly to look to. All of that is Old English for "he was a good-looking young man." As a matter of fact, later in the chapter, in verse 18, we find that David was a skillful musician, valiant(brave), a soldier, a prudent man (discreet), and comely (attractive). In other words, he wasn't a slacker. He looked good. He behaved well. He had talent, and he used that talent. He wasn't a wuss. He was a boy that parents would like to see coming to court their daughter. Not a thing to complain about concerning David.
Now here's my point. All of Jesse's sons looked good, including David. It wasn't that their outer appearance needed work; their hearts needed work. God is no respector of persons - he looks on the heart, no matter how good the outside looks. So to use I Samuel 16:7 to excuse slovenliness, immodest dress, laziness - pick your favorite sin and plug it in here - is doing a disservice to God's Word. It's taking this verse out of context in order to rationalize our sin, to give ourselves permission to do what we want to do. How many times have you heard it? "Well, God knows my heart." Yep, He sure does, but don't throw this verse back at Him. When He said this one, He had the sharpest boys around in mind. He wasn't talking about that family that bummed off everybody around them, looked like punks, and made everyone around them miserable. He was talking about men who looked like kings.
Now, lest we get to feeling a bit uppity because we do look so good on the outside - we dress right, talk right, walk right, eat right - remember the flip side of that coin. All those first seven boys looked really good; Samuel thought they all were worthy to be kings. But God rejected them because He knew their hearts. You can look good on the outside and still be filthy dirty on the inside. Man looketh on the outward appearance and says you look mighty fine, but the Lord looketh on the heart and finds us wanting when it's filled with pride.
I've never found any verse in the Bible that excuses sin. Nowhere have I found justification for doing our own thing. Yet this verse is used over and over again to rationalize everything away, down to "God looks on my heart." I'd like to see it used in context, to remind us that yes, we are to have standards and seek excellence, but in all that excellence to remember to make our hearts excellent as well, because God looketh on the heart, not all that good stuff on the outside.
Let me add that, in the area of weight control, I realize that there are some people who do have a horrible battle with it, and physically cannot lose the weight. What I'm addressing here is rationalizing problems with self-control by saying God doesn't care what I look like. A genuine medical condition can and should be supervised by a doctor, and is not a sin. Willful, deliberate indulgence of flesh is a sin, though, and shouldn't be rationalized away.
I'm done now! :)