Recent article in Lancet (www.thelancet.com/action/showFullTextImages?pii=S0140-6736%2816%2930175-1) of 10 million people worldwide still shows the "sweet spot" (lowest mortality) of Body Mass Index (BMI) is 20-25. The Nurses Health Study showed that exercise (150 MET/wk {brisk walking for 1 min is 1 MET} was the second most important factor for longevity (second only to not smoking). So never smoking (or stopping) is the most important factor for living longer. Regular exercise (150 MET/wk) is the second most important. See Primary prevention of coronary heart disease in women through diet and lifestyle. Stampfer MJ, Hu FB, Manson JE, Rimm EB, Willett WC. N Engl J Med. 2000 Jul 6;343(1):16-22. PMID:10882764