cardio fit weight loss

I am 53 years old and have a very slow time loosing I am doing weights withhim which s really making a huge difference with hiit intervals about 5 times a week also spin three ties a week, he originally had me on 1400 calories which I said really was not working so reluctantly said to try 1300 and Lon carb days (only from yogurt fruits and veggies) and on carb days about 3 a week only 60 and acting very clean except for two free meas a week and 3 litres of water well I am happy to say I am loosing 1 pound a week, may not sound like much but for me it is progress ad I am also gaining muscle but loosing inches!

I've never heard of cardio fit weight loss, but I would do some research on low carb and ketogenic diets.
1200 calories is not enough for your body to live on. I'm surprised anyone in the health profession would even suggest that.
You could also do some research on Basal Metabolic Rate and Total Daily Energy Expenditure.