There are ways to lose weight quickly, though you don't say how quickly or how much weight you want to lose. Some are logical but absurd, such as stop eating, take speed, and the like. But if you're looking to permanently lose weight and keep it off, doing it quickly might actually work against you. The key to permanent weight loss is to alter permanently your metabolism both in digesting food and in your energy output. You increase your metabolism by exercising or just moving more. You maximize your food metabolism by avoiding foods that metabolize very quickly into sugar and therefore must be burned quickly or it will store as fat. You eat a balanced diet of mostly non-animal based protein, lots of veggies, some fruit, and whole grains. It's not anything new or radical, but in the long-term studies going on all over the world this is still the overall best diet for both not getting obese and staying healthy. There are many fad diets, such as the many high protein diets popular today, and they might work well for you, but long-term data isn't so good on them. Tell us why you feel you need to lose weight quickly.
Are you getting ready for a one time event or looking for permanent weight loss? Paxiled is right. You can lose some weight very fast but it won't be permanent. and is often water weight. Fasting will do this. There are benefits to a fast and it's not a bad idea as long as you understand that it's a short term thing to do and the results will be quick. And then end. And then you are back where you started and perhaps even worse off.
Another way in my opinion to make a big impact is to overhaul your diet. Sugar, processed food and bad fats all reduced or eliminated quickly will impact you. Not overnight. But when I change my eating habits, I notice a pretty quick change in weight. Within a week I start to feel a little better and within a month, I have a result to show for it that continues to grow the longer I maintain the eating changes. I was a big soda/pop drinker. Loved it. L-O-V-E. It could have been my Valentine for the way I longed for it all day. ha. I gave it up cold turkey. Immediately I decreased calories with this on a daily basis. I did not do diet soda as I'm sensitive to artificial sweeteners so it was a good chunk of calories I was drinking daily. I really believe this quickly made a difference. Do you have anything like that which is a no brainer to do away with right away?
My new thing is timing of eating. I don't eat anything after 7 pm and only drink water or unsweetened tea. Then I don't eat again until after 7 am. (unless I wake up nauseous which can be due to low blood sugar for me and eating makes that better. This has happened a couple of times and then I have a bowl of oatmeal or a banana or something like that). That 12 hours helps. I try to get dinner in early, eat well at that time and then that's it. As I have been found in the kitchen after midnight with my hand in the cookie jar . . . giving up any night eating is helpful for me.
And this is just how I do it which has worked for losing weight--- I eat light breakfast, light snack, salad or something really lean for lunch, light snack and then a normal dinner with my family. I have kids and a husband so I try to make it a healthy dinner but I eat til full and whatever I make for them, I eat. Yes, I had mac and cheese yesterday along with my chicken and broccoli. I just had a small portion but dang, it was good. :>) Then that's it. Nothing else and to bed. Has worked for me.
And exercise. Don't forget it. It helps. I don't think anyone unless an elite athlete can loose significant weight from exercise alone--- diet is really the key to weight loss.
So, give us more details and we'll see if we can help!