Thinness warns us about our health.
Dream dictionary: Thinness dream meanings
Unless we are following a weight loss regimen in which case the dream shows our desire to succeed in that goal, the dream may be showing our fear or the harbinger of an era of economic or health hardship.
Seeing weve lost weight in dream is a warning that we must take care of our health, as diseases are around us. If we dream we are very thin, it means that the risk of disease is very close, and the thinner we see us, the more important it will be.