Lean, skinny (if they really are), as well as skinny, — mean problems, lack of money and experience.
If you dream you have lost weight, sleep may point to the trouble that will cause material losses, lack of money.
If in addition to thinness was painful, the dream indicates illness and serious disease. Often in these dreams is a reference to a body part or system of the body, which «failed».
If in your dream you saw a distressed other person, all of the above applies to the character of sleep.