You didn't provide your age, height, or weight, so there's no way for me to tell you if you'd lose the weight quickly. Going on what I generally know, however...
5-6 pounds is a lot of weight to lose even in a month, unless you're seriously overweight. Yes, your weight can fluctuate a few pounds due to water weight gained/lost, but what you're proposing is ridiculous, and extremely unhealthy.
Even if you could lose the weight, you wouldn't keep it off. You could try pretty much any unhealthy fad diet and you might lose a pound or two. If you're anywhere near your ideal body weight, though, you'll be out of luck.
I'm not trying to be mean, I'm just speaking from experience. I tried fad diets in the past. Now I run at least a mile every day and eat healthily, and over the past two months, I've lost maybe two pounds...but that's because I'm 5'4" and 120, with a lot of muscle mass. I'm pretty much at my ideal weight. Makes it hard for my body to lose any extra.
If you want to look good for your date, drink lots of water, don't overload yourself with carbs, stay away from refined sugar/sucrose, and hit the treadmill for 20 minutes per day (provided you're not an avid exerciser. If you are, try upping your cardio by 5 or 10 minutes, or doing a different type of cardio). You won't lose 5-6 pounds in a short time by doing these things, but you'll feel thinner and stronger. Even better, if you can keep it up for longer, you might eventually lose the weight you want, AND you'll keep it off.
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