Whey is the clear liquid that is left after cheese curds are removed during cheese making. It is often dried and used as an ingredient in other foods. Whey contains lactose, milk solids and protein. Hope this athlete isn’t lactose intolerant.
Weightlifters or bodybuilders who want to cut muscle (show defined muscles in competitions) often get sucked into taking protein or amino acid supplements. These supplements do not build muscle and combined with an already high protein intake, often stress their kidney function. You mention that this athlete is deficient in calories. If so, then he is burning food protein as a very expensive fuel. Unfortunately, weightlifters and bodybuilders sometimes don’t listen to reasonable nutrition advice while looking for the quick fix by sharply decreasing fat and increasing protein intake. Nancy Clark is an excellent source of sports nutrition information.
Has he tried my Healthy Body Calculator®? It will predict a healthy weight, even for lean athletes with a lower than average body fat as well as a personalized Your Nutrition Facts report based on their nutritional goals i.e. percent of calories from fat, protein, and carbohydrate as well as desired weight change.
If you are a member of the Academy of Nutrition and Dietetics, you can join an electronic mailing list (EML) for any of the practice groups that you paid with your Academy dues. I will forward a message to you about joining Academy electronic mailing lists (EML). There have been many discussions about creatinine and other protein supplements athletes take. I think you would find it beneficial if you are a member of the Academy. If you are not a member of the Academy, you will not be allowed to join.