Current issues of ACP Journal Club are published in Annals of Internal Medicine


Etiology

Weight loss and mortality in adults

ACP J Club. 1994 May-June;120:81. doi:10.7326/ACPJC-1994-120-3-081


Source Citation

Pamuk ER, Williamson DF, Serdula MK, Madans J, Byers TE. Weight loss and subsequent death in a cohort of U.S. adults. Ann Intern Med. 1993 Oct 1;119(7 pt 2):744-8.


Abstract

Objective

To study the effect of adjusting for preexisting disease and cigarette smoking on the association between weight loss and mortality in adults.

Design

Further analysis of a cohort study drawn from the first National Health and Nutrition Examination Survey (NHANES I).

Setting

United States.

Participants

2453 healthy men and 2739 healthy women between 45 and 74 years old who were recruited from 1971 through 1975. Vital status was determined through 1987.

Assessment of risk factors

Weight loss (the difference between self-reported maximum weight and baseline weight) was categorized as < 5%, 5% to 14%, and ≥ 15% loss. Maximum body mass index (BMI, weight [kg]/height [m]2) was used to divide participants into 3 strata: < 26, 26 to < 29, and ≥ 29. Data on age, race, parity for women, cigarette smoking, preexisting illness, and maximum BMI were collected.

Main outcome measures

{Death certificates and proxy interviews were used to verify deaths. Decedents for whom no death certificates were obtained (n = 48) were included in the mortality analysis but excluded from the analysis of cardiovascular disease (CVD) and non-CVD mortality}. (Information supplied by author.) Mortality data were analyzed by including all deaths and then by using deaths after 5 and 8 years of follow-up to limit the effect of weight loss caused by preexisting illness. Relative risk (RR) was calculated using mortality for weight loss < 5% as a reference category within BMI strata.

Main results

For men with maximum BMI < 29, but not for heavier men, weight loss > 15% was associated with increased all-cause mortality, even when early deaths were excluded. For all women, weight loss > 15% was associated with increased mortality. RR for CVD death was largely unaffected by adjustment in either sex. Limiting the analysis to persons who had never smoked did not substantially alter the results.

Conclusions

A history of weight loss was a risk factor for death in all but heavy men.

Source of funding: {Public Health Service.} (Information supplied by author.)

For article reprint: Dr. E.R. Pamuk, Division of Nutrition (K-08, Room 730), Centers for Disease Control and Prevention, 6525 Belcrest Road, Hyattsville MD 20782 USA. Fax 301-436-8459.


Commentary

Body weight changes and all-cause mortality: a reviewandWeight change and mortality in high-risk, middle-aged men

Treating a patient who is obese is not a trivial problem; it may occur rather frequently in the practice of internal medicine. Obesity is a risk factor for multiple disorders, from cholecystitis to cardiovascular disease and certain carcinomas. Yet, does a reduction in disease occur with a reduction in weight? These 3 articles, in a weight-loss supplement to Annals of Internal Medicine, provide some information about this topic.

The article by Andres and colleagues reviews the literature about the association between weight change and mortality. The authors specifically excluded studies that purported to show a relation between weight loss and decreased mortality, which were reviewed in an article in the same supplement (1). Some of the articles reviewed by Williamson and Pamuk (2) appear to support a reduction in mortality with a reduction in weight. Taken together, the medical literature does not convincingly show that weight loss is associated with increased longevity. The lack of evidence for decreased mortality with a decrease in weight should be of concern, however, because weight reduction might be expected to decrease the various diseases associated with obesity that are risk factors for cardiovascular mortality, such as hypertension and diabetes mellitus.

The second article, by Pamuk and colleagues, analyzes a cohort drawn from the NHANES I study. The principal purpose was to analyze the effect of cigarette smoking and preexisting illness on the relation between weight loss and increased mortality in this data set. The authors found that preexisting illness may account for some of the effect in the noncardiovascular deaths, but an adverse effect of weight loss on mortality still existed.

The third article, by Blair and colleagues, analyzed the effect of body-weight change in the MRFIT data set. This provided further evidence that weight variability is associated with an increased mortality rate. Those with either weight loss only or weight cycling tended to have the highest relative risks for mortality, whereas the lowest risk tended to occur in the stable-weight group. This adds further information that weight cycling, the repeated gain and loss of weight, may be detrimental to survival, as reported elsewhere (3).

Noteworthy limitations exist in these reviews. The studies reviewed were heterogeneous and included persons of various age groups. The authors of the reviews chose substantially different criteria for inclusion and exclusion. The length of follow-up observation was variable. The weight of the participants may have been biased because it was often taken from a history rather than by objective measurement. The issue of weight caused by adipose tissue, rather than lean muscle mass or edema, was not addressed. Generally, only 2 "measures" of weight were used, and these may not be accurate reflections of a person's lifetime weight history. Confounders, such as smoking status, were handled in various ways. They may have been excluded or adjusted for, or the status may not have been assessed.

Most evidence suggests that the main emphasis of health care efforts should be on the primary prevention of obesity through life-long maintenance of a normal weight. Of course, this segment of the population tends not to be seen in the practice of internal medicine. Sports or pre-employment physical examinations, however, may provide an opportunity for this type of intervention.

Management of the obese adult is a separate issue. Specifically, should he or she be advised to lose weight? The highest mortality risk group appears to be those with weight cycling. This type of behavior should be discouraged based on most of the evidence. For those who are at or slightly above normal weight, maintenance of that weight should be the goal. The picture is less clear, however, for patients who are morbidly obese. Convincing evidence of mortality reduction with weight reduction is not available. Yet, obesity is a risk factor for multiple morbid and mortal conditions. Consequently, gradual and sustained weight reduction appears most warranted at present.

Kurt Hegmann, MD, MPH
Medical College of Wisconsin Milwaukee, Wisconsin, USA