Pocrescophobia is the morbid and irrational fear of gaining weight. This is also comparable to Obesophobia, the fear of becoming fat or being obese.
Symptoms of Fear
Symptoms of Fear will vary from one person to the next, depending upon their state of mind, level of fear, and various personality characteristics. General symptoms, though, include avoidance of food, obsession with weight loss, avoidance of scales, guilt when eating, and not feeling hungry.

Treatments:
Treatments will vary from person to person. Typically, therapy is a great go to. Various forms of therapy can help get to the bottom of the phobia, as well as treat it. Social therapy is also a great method for building self-esteem.
Medication is useful for treating anxiety, as well as other symptoms (ex. rapid heart rate, breathing difficulties, etc.). This can be taken on a daily basis or just during a panic attack.
Lastly, rehabilitation centers for eating disorders are a great way to combat Pocrescophobia. These centers offer a warm and comforting environment to those who fear gaining weight or have low self-esteem.