How much weight can you possibly lose in two short days and what (natural) method should you use to achieve the best results? Let's say that you find yourself in a situation where you made arrangements to go to the beach three days from now, but you are not at all excited about the fact that your friends and other people are going to see your big belly. You completely realize that it is too late to achieve that elusive flat six-pack belly you always dreamed about. But you do want to lose as much weight as possible to minimize the horror your friends will inevitably experience when they see you in a bathing suit for the first time this year. You want results and you want them fast, but without endangering your health in the process!
What should I eat?
I know this will come as a surprise, but for the best results you shouldn't eat anything for the next two days (effectively you will be fasting). Normally, before a fast you need to properly prepare your digestive system for a fast. This means that you should be eating lots of fruits and vegetables (but only fruits and veggies!) a few days before a fast, so no putrefying foods will remain in your colon. But since this will only be a two day fast it is unnecessary.
What should I drink?
This might sound counter intuitive, but you really should be drinking sufficient amounts of water during the next two days. For most people this usually means about 3-4 quarts (3-4 liters) of water per day (that can also be increased especially in hot seasons and/or intense workout periods). Don't worry about retaining water since our kidneys are well versed in excreting the excessive water from our bodies. They are able to do so at about 1 quart (1 liter) per hour, so even if you did drink more than necessary, the extra water will be quickly dealt with. Since you won't be eating anything, you will also be removing all the water-retaining foods from your diet (mostly sodium-rich, salty foods). Because of that you will be excreting additional water that was stuck mostly in your belly area (to keep the excessive sodium diluted), which is an additional bonus. Drinking too little water actually works against you, since it puts the brakes on your metabolism (making you burn less fat), which is an additional argument why you should always be drinking sufficient quantities of water.
What about exercise?
If you want the best results, you will also need to exercise. What I would do is exercise at a low intensity and for longer durations. For example, instead of running for an hour (higher intensity training), I would be walking quickly for two hours (lower intensity training). At lower intensities you are burning a maximum percentage of calories from your body fat stores. This is determined by your maximum aerobic heart rate, but since most people don't have a pulse meter, I have a simple rule to follow while exercising. Whatever your activity of choice will be, you need to be doing it at a pace where you can still have a conversation easily. If you are exercising alone, you need to be able to comfortably breathe through your nose. If you are already at a high level of fitness, you can get great results with this.
Exercising like this will help you target your slow burning energy reserves most efficiently (body fat stores) while helping you burn out your fast-burning energy reserves (energy from the food still in your digestive tract and from the liver and muscle glycogen stores). Lower intensity will also help you feel less crushed afterwards. Once your fast-burning reserves are depleted (probably on the second day) you will enter full ketosis (a state where you are burning almost exclusively body fat for energy).
I have managed to lose over 5 pounds with this method, as you can see from my water fasting challenge. But let me tell you that this is not an easy method. Once you enter full ketosis, you will probably feel really tired, possibly even dizzy. If that becomes unbearable, you can eat something sugary, like a few dates or some honey to bring you back in business (without contributing to your weight too much). But you need to realize that this is a quick fix method and water fasting should never be "abused"(especially if you are tempted to do it for longer than two days). I would recommend a healthy and sustainable diet and exercise plan over such quick fixes for a vast majority of people.