If pure calorie burn/fat reduction rather than increased cardio fitness is what you are after the the 60% - 70% is better. It's something to do with how your body uses oxygen and creates energy. It called the fitness zone.
70% - 80% is the aerobic zone. You still burn calories but your body will convert less energy from fat and more from muscle.
80% - 90% the anaerobic zone. This is where you want to go for endurance training.
90%-100% red line. No-one can stay here for long.

I would say that you need to look at one or two sessions of resistance training a week. You can do it on the same days as cardio. The great benefit of resistance training is that it makes muscles and muscles mean that your body burns more calories at rest. It also creates stronger bones which your body will thank you for after menopause. Half the women in my Tuesday pump class are retired ladies with issues with bone density.
If you have no weights all the body weight exercises are great - push-ups, dips, squats, lunges.

Although it sounds counter-intuitive try not to work out when you're hungry but on the flip side don't reward yourself for a wok-out with food.