Well to put it in my perspective:
Im: 1.83m, originally 102kg and have dropped down to 95.2kg in 40 days, by simply calorie counting with "My Fitness Pal" - it's free online/Android and IOS devices.
I think my goals set were to lose 1-2lb per week in which i calculated i could eat 1800kcal, then i just simply dropped off to 1700kcal and have eaten to that ever since.
So yes, 3 months is very doable assuming the person is quite heavy with a high bodyfat percentage but for the average joe's out there, its not attainable by eating healthily!
*If any of you have/want to join Myfitnesspal, add me as a friend... nickname = krhn (remember to say your from TSR)*