There a lot of variables to consider when answering this? The nature of your question leads me to believe your not a gym rat. Now I have trained men and also women. A couple post pregnancy. One with very little experience like just wanted to get back into a swimsuit and feel confident the other was a little beast that now competes in physique.
Without knowing what end of the spectrum your at. All I can say is lead a healthy lifestyle that includes resistance training as well as cardio. Do it at least 4 days a week. Eat right. Don't "diet" just eat right. Diets are temporary. Your after a lifestyle change, not a diet and exercise program. There are no shortcuts, sure there are things we can do to improve the results but without effort no amount of anything you take will help. Good luck.