There is no solid evidence that cortisol blockers lead to weight loss.
When you're under stress, your body boosts production of the hormone cortisol. Chronic stress and persistently high cortisol levels may be associated with increased appetite and weight gain.
However, the connection between stress hormones and weight gain is largely based on anecdotal evidence, with only a few studies supporting it. Weight gain is influenced by many intersecting factors.
Some dietary supplements claim to block cortisol to aid weight loss. Seven marketers of such supplements were charged by the U.S. Federal Trade Commission with making false and unsubstantiated claims that their products produce rapid, substantial and permanent weight loss.
Bottom line: Steer clear of weight-loss products that make unproven claims. Instead, focus on reducing your calorie intake and increasing your activity level. For lowering stress, explore stress management techniques.