All of the super refined and processed sugars and fats we ingest, cause spikes in the metabolism that our body can only handle to a certain extent. The average human has faced a massive diet change in a reletively short time span. Nicotine is addictive I would think,
because of the spike. Your body struggles to compensate, then when the same rapid high level isn't there for an extended period, your body misses it.. big dose again.. repeat. The same would go for any food, ingestable... activity.. in the right or susceptable(sp?) person.
http://www.pubmedcentral.nih.gov/art...?artid=2235907