Science and faith aren't mutually exclusive. Exercise and weight loss cures diabetes, it also takes faith that what you're doing will work so you don't give up. Is it guaranteed? No, but neither is everlasting life. Is it fear of diabetes (or heart disease, cancer, etc) that motivates us to change our lifestyles and save ourselves? Quite possibly. Or it might be a fear of being unattractive. Fear is probably the most powerful motivator there is. Faith in God, even for reasons of self-preservation, isn't fear so much as it's fear replaced by faith. If we remove fear as a motive, or if we discount fear as a legitimate motive because it's inherently selfish, or because it's not up to Godly standards of belief, we remove so much motivation people have to make so many good things happen for themselves and others, I wouldn't have faith anymore that anything would ever get done.