My friend's blood test came back with alt at 283 and ast at 123. with enzymes so high, what could it mean?

Get worked up: His physician will probably repeat these with him off alcohol and all meds after two weeks. If they're normal, that's his warning. If not, a workup for hepatitis b, hepatitis c, autoimmune hepatitis, hemochromatosis, wilson's and antitrypsin deficiency as appropriate. If none is found, he may perhaps have recommended an even more fitness-focused lifestyle. Best to you both.