Dreams of growing fat depend on the individuals who have them. If the individual has a normal body weight and is not concerned about the way he looks, dreams about growing fat are usually good omens and foretell happy times to lie ahead in one's waking life. To grow fat in this case stands for progress, evolution etc. - such as increasing one's gains, having a fruitful relationship etc.
Seeing others growing fat in dreams is usually a good omen, too, and represents abundance, magnitude, richness and well-being.
On the other hand, growing fat dreams are very common among people with eating disorders and among those who fear gaining weight. In this case, such dreams reflect people's anxieties and their fear of weight gain, both of which arise from low self-esteem and not feeling able to control themselves.
To see yourself suddenly growing fat in your dream also stands for overindulgence.