Oxymetholone (also known as anapolon or anadrol) is a very drastic synthetic steroid, 17-alpha-alkylated modification of dihydrotestosterone. It was developed for the treatment of osteoporosis and anaemia, as well as to stimulate muscle gain in malnourished and debilitated patients. Oxymetholone has been approved by the American Food and Drug Administration (FDA) for use in humans. Later there where created non-steroidal drugs that effectively could treat anaemia and osteoporosis; because of this anapolon lost his popularity and by 1993 Syntex decided to cease the production of the drug, as well as other manufacturers did.
The common side effects of oxymetholone include depression, lethargy, headache, swelling, rapid weight gain, priapism , changes in skin color, urination problems, nausea , vomiting , stomach pain (if taken on an empty stomach), loss of appetite, jaundice , breast swelling in men, feeling restless or excited, insomnia , and diarrhea .  In women, side effects also include acne , changes in menstrual periods , deepened voice, hair growth on the chin or chest, male pattern baldness , enlarged clitoris , and changes in sex drive .  Because of its 17α-alkylated structure, oxymetholone is highly hepatotoxic . Long term use of the drug can cause a variety of serious ailments, including hepatitis , liver cancer , and cirrhosis ; therefore periodic liver function tests are recommended for those taking oxymetholone. 
Although I am usually not inclined to posit speculations on why a particular drug does or doesn't do something, in this case I will. Im guessing that the higher doses of Anadrol cause enough appetite suppression (at least anecdotally) to make eating rather difficult. It can also increase insulin resistance and glucose intolerance (5). This has the effect of making macronutrient absorption more inefficient, and could also be a factor in reducing gains when the dosage goes over 100mgs/day. Unfortunately, Anadrol also has a reasonably profound effect on your body's natural hormonal system, on par with most other oral steroids , but not as bad as most injectables, and its certainly not as harsh on your lipid profile as many anabolics are