What is the consensus in the medical community about the validity and/or wisdom of the "DNAFit" genetic analyses?
No consensus . This testing is too new for there to be any medical consensus opinion. However I don't believe you need sophisticated genetic testing to eat a healthy diet and plan an exercise program. I suspect the recommendation for most people is going to be a healthy diet with lots of fruits and vegetables limited amounts of meat and reduced intake of refined carbohydrates.
Genetic analyses.. can be very enlightening particularly when screening for a serious inherited condition/disease. Genetic analyses can identify a tendency toward some multifactorial conditions including heart disease/cancer. But its reliability in choosing an individualized diet or fitness program is overstepping its capability, I believe. Also, remember labeling oneself with genetic markers may affect insurability.