Excess weight is protective in the elderly? New research says no

Obesity is a known health risk. The number of epidemiological studies that have linked excess weight to cardiovascular disease, cancer, diabetes, other chronic conditions, and increased risk of death is staggering.1,2 In fact, the cutoff points for BMI into overweight and obese were created to reflect increased risk of disease and death due to excess fat.3

Photo of obese man

Then there is the “obesity paradox.” This is the term used to describe the opposite of the usual finding - there are certain groups of people, usually those with severe chronic diseases such as heart failure and kidney disease, in which a higher BMI seems to be associated with a decreased mortality risk.4,5

Elderly persons are another group in which an obesity paradox has been observed in some studies.6 However, this observation is not consistent – other studies have reported an increased risk with higher BMI in adults over age 70 or 75, similar to younger age groups, and others have shown no association at all.7-11 Overall, the relationship between BMI and mortality in the elderly has been unclear.

Several explanations have been proposed to explain the paradox – these are a few examples:

  • BMI is not a true indicator of body fat – older persons tend to have more body fat at the same BMI as younger adults.3 One study found that greater waist circumference in the elderly was associated with increased mortality risk, but greater BMI was associated with decreased risk. In these individuals, greater BMI may reflect greater fat-free mass, rather than greater body fat. Waist circumference and fat-free mass may be more important indicators than BMI for obesity-associated health risks in the elderly.12,13
  • Unintentional weight loss may be involved – many older persons in these studies who are at a low or normal BMI may be there because of disease-related weight loss. Weight loss in elderly has been shown to be associated with negative health outcomes, presumably for this reason.14 So a study of elderly persons that only takes one weight measurement and does not measure weight change over time is inherently flawed.
  • Another issue with the length of studies is that weight gain late in life is probably less dangerous than weight gained earlier in life and then maintained for many years – being obese for 50 years results in more cumulative damage than being obese for 15 years. The earlier you become obese, the greater the risk of death.15,16 Therefore, long-term data (decades, not years) is needed to get an accurate picture of health risks in the elderly due to obesity.

Newer research attempted to reconcile the contradictions in previous studies by using long-term data. Although the researchers used BMI rather than waist circumference, they used two weight measurements 17 years apart, and followed subjects for a total of 29 years – importantly, they only included subjects who maintained a similar weight over the first 17 years – this helped to remove any potential effects from late life weight gain or disease-related weight loss.

Men (age 75-99) who maintained a BMI greater than 22.3 had a shorter life expectancy by 3.7 years, and an 88% increased risk of death during the study period compared to men with a lower BMI. Men who maintained a BMI greater than 27.3 had double the risk of death compared to those with a BMI less than 22.3. Women in the same age group who maintained a BMI greater than 27.4 shortened their life expectancy by 2.1 years, and had a 41% increase in risk of death compared to women with a lower BMI.17,18

This study leads us to conclude: no matter what your age, carrying excess weight for a significant length of time is dangerous – in fact, it can be deadly.

 

References: 

1. Guh DP, Zhang W, Bansback N, et al: The incidence of co-morbidities related to obesity and overweight: a systematic review and meta-analysis. BMC public health 2009;9:88.
2. McGee DL: Body mass index and mortality: a meta-analysis based on person-level data from twenty-six observational studies. Ann Epidemiol 2005;15:87-97.
3. U.S. Centers for Disease Control and Prevention: About BMI for Adults. http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html. Accessed
4. Oreopoulos A, Padwal R, Kalantar-Zadeh K, et al: Body mass index and mortality in heart failure: a meta-analysis. Am Heart J 2008;156:13-22.
5. Schmidt D, Salahudeen A: The obesity-survival paradox in hemodialysis patients: why do overweight hemodialysis patients live longer? Nutr Clin Pract 2007;22:11-15.
6. Oreopoulos A, Kalantar-Zadeh K, Sharma AM, et al: The obesity paradox in the elderly: potential mechanisms and clinical implications. Clin Geriatr Med 2009;25:643-659, viii.
7. Calle EE, Thun MJ, Petrelli JM, et al: Body-mass index and mortality in a prospective cohort of U.S. adults. N Engl J Med 1999;341:1097-1105.
8. Janssen I, Mark AE: Elevated body mass index and mortality risk in the elderly. Obes Rev 2007;8:41-59.
9. Grabowski DC, Ellis JE: High body mass index does not predict mortality in older people: analysis of the Longitudinal Study of Aging. J Am Geriatr Soc 2001;49:968-979.
10. Kuk JL, Ardern CI: Influence of age on the association between various measures of obesity and all-cause mortality. J Am Geriatr Soc 2009;57:2077-2084.
11. Stevens J, Cai J, Pamuk ER, et al: The effect of age on the association between body-mass index and mortality. N Engl J Med 1998;338:1-7.
12. Janssen I, Katzmarzyk PT, Ross R: Body mass index is inversely related to mortality in older people after adjustment for waist circumference. J Am Geriatr Soc 2005;53:2112-2118.
13. Zamboni M, Mazzali G, Zoico E, et al: Health consequences of obesity in the elderly: a review of four unresolved questions. Int J Obes (Lond) 2005;29:1011-1029.
14. Woo J, Ho SC, Sham A: Longitudinal changes in body mass index and body composition over 3 years and relationship to health outcomes in Hong Kong Chinese age 70 and older. J Am Geriatr Soc 2001;49:737-746.
15. Adams KF, Schatzkin A, Harris TB, et al: Overweight, obesity, and mortality in a large prospective cohort of persons 50 to 71 years old. N Engl J Med 2006;355:763-778.
16. Sun Q, Townsend MK, Okereke OI, et al: Adiposity and weight change in mid-life in relation to healthy survival after age 70 in women: prospective cohort study. BMJ 2009;339:b3796.
17. Singh PN, Haddad E, Tonstad S, et al: Does excess body fat maintained after the seventh decade decrease life expectancy? J Am Geriatr Soc 2011;59:1003-1011.
18. Contrary to Earlier Findings, Excess Body Fat in Elderly Decreases Life Expectancy. 2011. ScienceDaily. http://www.sciencedaily.com/releases/2011/08/110811151325.htm. Accessed September 29, 2011.

 

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Comments (2) Read through and enter the discussion with the form at the end
Stephen - October 12, 2011 10:21 AM

The lack of individualized benchmarks for optimizing lifestyle are a major flaw in the preventative health industry.

This article brings together a significant amount of research which helps to establish BMI benchmarks for improved health.

As the article indicates, BMI is a helpful indicator but is not perfect. Percent body fat has potential but is hard to measure and most available methods are inaccurate.

What is needed is a cocktail of indicators that, taken together, can be used to optimize health and longevity.


Jennifer B - October 12, 2011 2:13 PM

I appreciate the clarification about why lower weight elderly might have a shorter life expectancy; ie they were overweight their whole life and have had recent weight loss due to disease. It's so important to be able to examine these studies and think critically about them.
Thanks!
Jennifer B

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