Many people are under the misconception that if you eat less and exercise more, you'll speed toward your fitness goals. Usually, the reality is, that this doesn't work at all, unless all of the variables lined up. The reason that this concept doesn't usually work, is that it's missing some key factors.
1st is that most people aren't really overeating. In fact, they are under eating and eating the wrong types of food. So a good nutrition plan where you are eating the right types of food (lean proteins, good fats and fibrous carbs), the right amounts of food (calorie intake), and the right frequency of meals ( approximately 6 evenly sized meals spaced apart no more than every 3 hours) is the foundation upon which your fitness program lies.
2nd is most people don't do any / or enough resistance training or the right method of resistance training. Muscle is the key for optimal metabolism performance and fat loss. Metabolic resistance training combining strength and faster circuit type work is the second key factor behind the nutrition plan.
3rd is people do too much steady state cardio without the other two factors. If you eat like a bird and do 8 hours on the treadmill every day, your hurting your body and killing your fat loss efforts. Your body stays in a muscle eating, catabolic state and is hormonally readjusted to retain and store more fat. So to cut down on time spent on cardio and maximize calorie burn throughout the day, targeted fat loss cardio is the final phase. Targeted fat loss cardio combining high intensity interval training and challenging steady state cardio training with a brief pause in between activates the 3 phases of fat burning (mobilize, transport and oxidize).
By implementing a good nutrition plan, metabolic resistance training and targeted fat loss cardio, you will build muscle and burn fat while achieving the results that you are looking for.