It is because of poor high-fat diet studies like this that high-fat diets get such a bad rep. Another study has found that those studying a ketogenic  (one that will create ketones in the body) or high-fat diet is not accurate unless it lasts for at least  2-3 weeks. Studies that are a shorter length of time have not effectively allowed the body to convert from using glucose to ketones as energy. Therfore, studies like the previous mean little.
Although the evidence is still slim with the many variations of dietary regimes athletes have, the Brazilian Olympic Wushu (kung-fu) team eats a high-fat diet. It is nice to see that even elite level athletes can eat a high-fat diet and still perform at an elite level.