There is no solid evidence that cortisol blockers such as CortiSlim lead to weight loss.
Manufacturers of cortisol blockers claim that high stress levels increase your body's production of the hormone cortisol, which in turns increases 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. More important, there's no evidence that blocking cortisol results in weight loss.
Indeed the Federal Trade Commission charged the marketers of some cortisol blockers with making false and unsubstantiated claims about their products' effectiveness for weight loss. As a result, the companies had to pay millions of dollars in refunds and to stop making unproven claims about their products.
Bottom line: Steer clear of weight-loss products that make unproven claims. Instead, focus on reducing your calorie intake and increasing your activity level.