To lose 1 pound you need to burn off 3500 calories. If you are at a weight and you are maintaining your weight, you can cut back your daily caloric intake by 500 pounds a day and you will lose 1 pound per week.
Most people intake between 1500 and 2000 calories a day, so taking off the 500 calories is fine. You should not try to take off 1000 calories or more a day, as it is too taxing on your body. Many of the calories you eat everyday are used for bodily function. Up to 60% of your daily calories are used for breathing, digesting, the circulatory system, organ function, and anything else your body does.
Still assuming you are maintaining weight, you can additionally lose another pound a week. If you take off 500 calories from how much you eat, then you can also burn 500 calories a day by exercising. Again you will lose another pound per week, from your current weight.
You cannot and should not use either of these methods alone and lower your calories by 1000 calories a day. If you did this with exercise you would not have enough energy for all of your bodily functions. After enough times of doing this you could become sick because of how your body reacts to not taking care of itself. If you wanted to cut 1000 calories a day from your diet, your body won’t receive enough nourishment each day, and you might start plateauing when trying to lose weight. Neither of these methods is healthy, so please avoid them.
On the other hand if you want to gain muscle by exercising and lowering your daily caloric intake by eating better, you are on a much better path. Muscles will help you burn your calories quicker, while eating the right foods will feed your body so that you are strong and healthy.
The problem with taking in too many calories and exercising a lot is often, it is difficult to bypass the caloric intake that way. High fat foods are packed full of empty calories. This means you become tired, lazy and even miserable. These things influence many people so that they will not exercise, thus causing even more weight gain.
If however, you are not maintaining your weight now, you should start by paying close attention to your calorie intake. Chances are it far outweighs your daily needs for bodily functions. You can also start exercising, to take off the daily calories you are adding on. Try to stabilize your weight by paying close attention to your daily eating habits and how much you exercise. Once you know what is out of order you can maintain your weight better and then start losing weight following the advice above.