Have you stopped and thought about the difference between condemnation (something not of Christ) vs. conviction (something good we all can do when there is a change needed in our lives) - “Therefore there is now no condemnation for those who are in Christ Jesus” Romans 8:1 (NIV)
I think our humanness, amplified by mass media, causes us to think something is wrong with us when we do not conform to “the norm”. Consider the amount of money spent on weight loss and the lengths people go to attain “thin is in”.
Condemnation comes from the enemy where conviction from the Holy Spirit. Condemnation will lead us away from God, whereas conviction will turn us towards Him in faith and trust to guide us. Condemnation causes despair and self-pity and conviction will give hope. When we know we need to do something to maintain our temple we should have conviction, never condemnation. Conviction is that unshakable belief without the need for proof or evidence- “You may ask me for anything in my name, and I will do it” - John 14:14 (NIV). It should have nothing to do with how you look or what media says. God has blessed us with life so therefore we have a responsibility to live as healthy a life as possible. Anyhow, I can't remember seeing anything stating what size we should be.
If we can keep our focus on living healthy (physically, spiritually and emotionally) we are doing our part to honor God- “you were brought at a price. Therefore honor God with your body.” - 1 Corinthians 6:20 (NIV)