This is not very specific. It depends on many factors:
-All of the above
As you can see, there is no one simple answer here.
The easy answer here is a combination of aerobic conditioning and strength training – no different than what it takes for men to maintain their health & improve their fitness level. But as Harris pointed out, there is no generic answer here. Give some more details & I’m sure you’ll get some more meaningful feedback.
The best exercise for anyone is an exercise that they will do, do correctly, and one that they have access to any necessary equipment to do. So, the BEST exercise is determined by the circumstance at the moment that you are going to exercise.
Choosing the exercise is usually the stumper. That is why I teach being able to think as you go. Be ready to switch to an alternative exercise, etc.
You are asking two questions.
The first asks about women’s health. The second mentions fat loss. Fat loss in certain circumstances is part of a woman’s health, though not always, and it is never a fact in isolation of many other circumstances.
As Harris suggests there are many factors at play. And a part of the role of anyone who works in fitness is to address the unique needs of each person. If you determine that fat loss is part of what needs to be addressed it will best be addressed not by one ‘best’ method, but by using a number of tools in the box together. Cardiovascular exercise, weight bearing exercise, meditation, nutritional counseling, yoga, social engagement and support….. many things have a role.
The best exercises for women are dependent upon individual abilities and goals. Many factors go into maintaining health for women–cardio, strength training, calming exercise such as yoga, nutrition, stress reduction, lifestyle, and a supportive environment. Fat loss can also also dependent on these factors, and then we need to factor in women’s hormones on top of all this (which can be a big issue with regard to fat loss for many women). It can be a balancing act to put it all together.
So, as you can see, there are many answers to your question!