Hello!! Personally, I would say that his goal is achievable, meaning he could achieve it, but it's simply not realistic. Losing 10 lbs in a week is dangerous to the body, since it is that quickly, therefore I would say that it is not realistic.
I hope I have helped. Have a great night and a Happy New Year!!
Change diet and lose weight
Controllable risk factors include:
Smoking.
High LDL, or "bad" cholesterol, and low HDL, or "good" cholesterol.
Uncontrolled hypertension (high blood pressure)
Physical inactivity.
Obesity.
Uncontrolled diabetes.
Uncontrolled stress and anger.