Food or no food doesn't matter. I started clen today at 20mcg first cycle. Felt fine... This was this mining but I take after a work out as don't want to take before due to it will prob ruin yr workout. I'm on 20mcg for 5 days, the 40 for 2, day off, 40 for 2 and 2 daya off etc. Advice from an experienced bodybuilder friend... 2 weeks on 2 weeks off yr bod gets used to it, tho everyone is different.... Keep your body guessing though