Zone Diet – is it truly healthy for any human being?

Zone Diet.  According to Webmd, You build your plate with 40% carbs, 30% fats,
and 30% protein.  Every meal has the same makeup.  You eat 3 meals a day
and 2 snacks a day.  It is a weight loss program that focuses on losing
fat, not water or muscle.  The foods you eat in the Zone diet help keep
your insulin levels within the therapeutic zone, hence the name of the
diet itself.  The diet includes foods like fresh veggies, fruits, nuts,
leafy green vegetables and of course plenty of water. You need to count
your calories when following this diet. For women, it’s caloric intake
should be about 1200 calories a day while men should be around 1500.
(WebMD)

Based on the information above, Is 1200 calories realistic and safe for the human body?  Are there certain medical conditions that this diet wouldn’t be safe? such as diabetes, renal issues, liver problems, etc.?   Is counting calories realistic?  Is anything about the information given not safe? 

Need 100-150 words, credible references and plagiarism free