I am taking 20mgs lexapro (escitalopram). will this make losing weight more difficult and my weight training less effective per workout ?

No: Lexapro (escitalopram) should not your weight or work - out

Carb cravings: Escitalopram (Lexapro) increase available serotonin in the brain - this can cause an increase in both hunger and cravings for carbohydrates. In addition, antidepressant SSRI's like escitalopram can adversely influence lipid and carbohydrate metabolism, leading to weight gain. On the flip side, people who are anxiety and depression eaters may experience decrease appetite on meds, and lose weight.