1.why should competitive athletes avoid high-fat meals? 2.why are high-protein diets considered dangerous? 3.how is carbo-loading achieved?  

Most protein diets have red meat and full fat diet products which increase your risk of heart disease. It may worsen kidney function in people with kidney disease because they may have trouble with eliminating all the protein metabolism. 

1.
High-fat meals are usually low in carbohydrates, which limits the amount of glycogen that can be stored for competition energy.
2.
High-protein diets are very high in fat, they encourage the body to get rid of water, and they can lead to osteoporosis, heart disease, and certain types of cancers.
3.
Carbo-loading is achieved by increasing carbohydrate calories to 60 to 70 percent of daily calories while slightly decreasing workout duration and intensity several days prior to competition.