Coleus forskohlii extract supplementation in conjunction with hypocaloric diet reduces risk of factors of metabolic syndrome in overweight and obese subjects: a randomized controlled trial 

In a randomized, double-blind controlled trial from 2015, 30 overweight or obese participants were given either 250 mg C. forskohlii extract or placebo twice daily for 12 weeks. Participants in both groups were to follow a hypocaloric diet throughout the study. At the end of the study both groups had significant reductions in hip and waist circumference and increased HDL cholesterol levels. However, only the treatment group had significant improvements in insulin levels and insulin resistance compared to placebo. 

References:

Loftus HL, Astell KJ, Mathai ML, Su XQ. (2015). Coleus forskohlii extract supplementation in conjunction with hypocaloric diet reduces risk of factors of metabolic syndrome in overweight and obese subjects: a randomized controlled trial. Nutrients. 7(11):