My wife and I got married when we both were 20. We are now 37, and I have lost sexual interest for my wife. I can't stop admiring young female body and not only am not sexually aroused by my wife (after she had 2 children and gained body width and 20 pounds of weight since we met), but I am disaroused of physical contact with her. She wants/needs sex, I do too, but it's not working. Anyhow with similar experience? How did you deal with it?
Work on your relationship overall, not just sex. Pray with her. Pray for God to renew your love for her. Stop looking with lust at younger women. Matthew 5:28 warns against this. God sees adultery in the heart, even if you aren't acting on it apart from looking.
She is your wife, and she has a right to sexual satisfaction, so don't slack off. Be the man. She shouldn't have to chase you for it, especially if it is weird for her to do so. So keep initiating like when you were younger. Pray for God to give you a heart for your wife like Proverbs 5 describes. Sometimes relationship issues can also make you less attracted.
On a practical note there are things you can do besides dimming or turning off the lights. Start working out and ask your wife to do it with you. Do it as a married couple activity. You could run or play tennis or some other aerobic activity designed to help her lose weight and help you both stay in shape. You could also work on your diet together. Replace that gallon bucket of ice cream with celery sticks with no fattening dip.
