Is 1200 to 1400 calories daily OK to lose weight sensibly?

Probably. It depends on your age, gender, activity level, height, and goal weight. Use a BMR calculator (easy to find online) and enter your information and your goal weight rather than your current weight. Then eat close to the calorie amount listed for your BMR.

For example, the calories needed to maintain a 25-year-old woman who is 5'6" at 130 pounds is about 1,400 calories. If that woman ate 1,300 calories a day and also burnt another 400 calories a day through normal activity and exercise, she would lose about a pound of fat per week. No one should eat less than1.000 calories a day without the supervision of a doctor.

depends on your age your weight and your height and whether you're a female or male

Forget calories.

1400 calories of pure carbohydrate could see you gain weight.

1400 calories of fat and protein would cause you to lose weight.

We process different foods differently, for example a kilo of hay contains 3200 calories none of which we could use. but horses could.

I've done less than that and here I'm 16kg less :D

Consult with your doctor.

Go vegan. Do enemas with non gmo coffee and non gmo lemons.

Depending on how old you are and how much you weigh, it may be reasonable.