Amino acids are an important building block in muscle gains. If you are taking amino acid supplements and exercising regularly you will see a gain in mass and strength, since muscle is denser than fat you will in fact gain weight. This weight gain however will be healthier than weight gained by improper diet and inactivity, the weight you will lose will be the calories you burn while building muscle. If you want to burn fat and minimize bulky heavy gains I suggest you do exercises involving only body weight or light weights at a moderate to quick speed and a high number of reps and cut out the junk food. So short answer no they will not cause weight loss but they are benificial and necessary for muscle health.
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