If your diet and cardio are both in check clenbuterol can have dramatic results. Like anything else it will not be very effective if you are not eating correctly. I find that 3 weeks while carb cycling and doing HIIT every day will melt off the fat better than anything else I have tried. My body tolerates it better than fat burners or ephedra with very slight nervousness and/or headaches when I first start my cycle(this is normal). As long as you gradually up your dosage you can minimize almost all sides. I start with 20mcg for days 1&2,40mcg days 3-5,60 mcg day6-9,80mcg day10-14,60mcg 15-17,40mcg 18&19,20mcg 20&21. Then I take caffeine tabs/fatburner for the next 2 weeks so there is not as much of a let down(I buy green tea tabs for $5 at walmart). For a first cycle I probably would not exceed 60 mcg/day but It all depends on your tolerance level. As far as long term sides I really havent heard of anything but I am not sure on that one. Many will say an ECA stack is somewhat comparable but I have not tried this and as far as over the counter products are concerned I have never taken anything that comes close to clen. Hope this helps.