If i go on a low calorie diet all week and just every saturday have a meal i enjoy and a few pints of cider, will i still lose weight?

Your cardiac history: is important considering you've been on a Holter monitor, had a stress test done before. Low calorie diet indicates that you are overweight or worried about gaining weight? If you exercise, you burn calories. Work with a clinical nutritionist to make sure you have a nutrient dense diet, and not one with minimal calories, or you'll be approaching it from the wrong angle.