Some people take crystal meth specifically to experience the side effects. As it causes a decrease in appetite, increased energy levels, and an increase metabolism, some users take crystal meth as a weight-loss aid. Crystal meth also tends to increase libido, leading to abuse of the drug for that purpose alone.ide Effects. Other side effects of crystal meth include: 1  Loss of appetite/significant weight loss. 2  Change in sleeping patterns. 3  Severe mood swings. 4  Unpredictable behavior. 5  Tremors or convulsions. 6  Elevated blood pressure.