Green coffee bean is high in a flavonoid called Chlorogenic acid. Flavonoids are powerful antioxidants and free-radical fighters that have been clinically proven to assist with blood sugar regulation, appetite control and reducing that hangry feeling! 
Regulating your blood sugar ensures that insulin doesn’t increase above normal levels, too much insulin and your body will store excess fat and may eventually lead to the development of diabetes.
Green coffee bean can act as an appetite suppressant, making it easier to avoid unnecessary snacking and reduce cravings. This will in turn assist in staying within the daily recommended calorie intake and avoid excess fat gain. Chlorogenic acid has also been recognised for its ability to lower triglycerides, LDL-cholesterol, and VLDL (a type of cholesterol)  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3766985/
Antioxidant and anti-inflammatory
Coffee is actually one of the highest sources of antioxidants in the average American adult’s diet, due mostly to the fact that we all drink a ton of it!
As mentioned, green coffee bean is higher in chlorogenic acid than its roasted counterpart, providing the body withmore of the powerful antioxidant compound and helping to protect cells from damaging free radicals.
Chlorogenic acid is also a known anti-inflammatory powerhouse and initial studies have shown it may help protect the function of your heart and liver. https://pubmed.ncbi.nlm.nih.gov/19022950/ 
Blood pressure and metabolic improvement
An 8-week study undertaken on 50 people with various metabolic syndrome symptoms showed that supplementing with green coffee bean daily can make a dramatic improvement to a wide variety of health and obesity risk factors in conjunction with a balanced calorie intake.
The group who were supplemented with 400mg of decaffeinated green coffee bean extract twice daily showed far more significant improvement in their fasted blood sugar levels, blood pressure and a greater reduction in their waist circumference than the control group who were given a placebo.
https://pubmed.ncbi.nlm.nih.gov/29307310/  .