Hi Josiekat I quit smoking last year for six months and I noticed a increase in energy right away I acually lost weight juring that period, probably cause I could push myself alot harder with exercise but I developed a sweet tooth I never had before. I'm smoking again but have set a date for June to quite again I noticed right away that my metabolism got better I know alot of people's metabolism slows but running really helped rev it up, in fact I feel that it is just starting to slow on me now which is why I'm quiting again. Good luck to you don't give into the craving like I did it's just habit.