I suppose you mean you're going to stop eating meat and go for a vegetarian diet for a week and see if it can help you lose weight. Couple of points I would like to clarify.
1. Animal meat can indeed do more harm than good since it leaves tons of acidic ash after digestion. Not only that, animals produce toxins under extreme stress, fear, rage or other negative emotions when they're slaughtered for food. These toxins will mingle with the meat and go right into your mouth. Oh, do not forget that if the animals are not reared organically, growth hormones and antibiotic residues will enter your body too.
Because of so much damaging things getting into your body causing hormonal imbalance and metabolic disorder, stop eating meat does help you lose weight by improving your overall health and, fix your metabolism. But a week of meat-free diet is not enough to see much weight loss result especially when your body has been heavily inoxicated in the past.
Taking vegetarian diet for a week, at best, can help you flush out certain portion of toxic waste. Your body needs to be cleansed at least 50-70% (depending on individuals' lifestyle) before you can start seeing significant result in weight loss.
Here, I suggest stop eating meat for more than a week, like 2-4 weeks. This should help you lose weight better. But keep it going because once you go back to your meat diet, toxins will accumulate and metabolism goes into disorder again, and the vicious cycle continues.
2. You may not lose weight even when you stop eating meat because calorie still counts. If you do not track the quantity of calorie going into your body, you can easily heap on excess calories and therefore, gain weight. On top of that, you must know how to make your meat-free diet tasty. If not, you would find it difficult to stop eating meat for weight loss.
Having said that, go find some free yet yummy vegetarian weight loss diet and learn about the mix-and-match of the ingredients. From there, you can simply follow the meal plan, swap or adjust the ingredients to suit your palate and needs.
If you decide to go without a vegetarian diet plan, then you must make sure you eat nutritiously because consuming the right nutrients for your body aids in boosting metabolism. In short, stop eating meat can help lose weight provided you have both the correct calorie intake and nutrients for your body.