Flegal et al (2013) conducted a meta-analysis of over 100 previously published research papers connecting body weight and mortality risk among 2.88 million study participants living around the world. Using standardized BMI categories (WHO 1997) relative to those classified as normal weight:
- Overweight individuals actually have a significantly lower all-cause mortality.
- Those classified with Grade 1 obesity did not have higher a mortality overall
- Those with Grades 2 and 3 obesity were associated with significantly higher all-cause mortality
Possible explanations of these finding include:
- Overweight and obese people may get better medical care.
- Heavier people may have better survival during a medical emergencies such as infections or surgery.
- Reverse causation, implying being sick can make you thin.
- Studies showing contrary results used a variety of different BMI categories with different cut-points for the various weight groups.
- Overweight people in theses studies who tend to live longest may not be fatter than most people at all, but in fact, average weight, since 33% of U.S. adults are clinically overweight and an additional 36% are obese.
Flegal KM, Kit BK, Orpana H, Graubard BI (2013). Association of all-cause mortality with overweight and obesity using standard body mass index categories: a systematic review and meta-analysis. JAMA. 2013 Jan 2;309(1):71-82.
Those who maintain their normal weight are less likely to be killed in a car accident.
New York Times, March 7, 2006, pg D6.
In the US, obesity accounts for between an estimated 0.30 and 1.08 years of population life expectancy at birth, depending on gender, ethnicity, and severity of obesity.
Olshansky SJ, Passaro DJ, Hershow RC, et al. (2005). A potential decline in life expectancy in the United States in the 21st century. N Engl J Med. 352,1138-45.
Obesity decreases life expectancy by six years, on average (Cooper 2003).
Excessive body weight increases the risk of death from all causes.
J Stevens, J Cai, ER Pamuk, DF Williamson, MJ Thun, JL Wood (1998). The effect of age on the association between body-mass index and mortality. New England Journal of Medicine, 338(1): 1-7.
The best mortality rates are those 25 to 30 percent over ideal recommended weight (Gaesser, 1996).
Greater body fat has a protective effect against osteoporosis (Felson, et al., 1993), lung cancer (Kabat & Wynder, 1992), and breast cancer (Wallace, et al., 1982).
Weight loss for overweight individuals may fail to improve health and can actually increase mortality rates (Andres, Muller & Sorkin, 1993).
Thin, under active men have 2.5 times the death rate than active, overweight men.
There is no clear-cut evidence substantiating obesity causes poor health and reduced longevity (Gaesser, 1996; Ernsberger & Haskew, 1987).
No relationship exists between body fat and degree of artheroscleritic buildup in coronary arteries (Barett-Connner, 1995; Kramer, et al., 1993).