How spontaneous or neurotic you are could dictate how much you weigh, says a new study.Yes, that’s right -- type A personalities and impulse shoppers are more likely to go through cycles of losing and gaining weight, according to research recently published by the Journal of Personality and Social Psychology.In the first study of its kind, three researchers from the Department of Health and Human Services followed nearly 2,000 subjects over a 50-year life span.