Body weight changes and all-cause mortality: a review
ACP J Club. 1994 May-June;120:80. doi:10.7326/ACPJC-1994-120-3-080
Andres R, Muller DC, Sorkin JD. Long-term effects of change in body weight on all-cause mortality. Ann Intern Med. 1993 Oct 1;119(7 pt 2):737-43.
To review literature analyzing long-term weight loss and all-cause mortality.
A comprehensive bibliographic review of population-based studies that assessed weight change as an independent variable and overall mortality rate as a dependent variable.
Studies were selected if mortality rates were assessed after body weight changes had been established. 6 articles purporting to show a decrease in mortality with weight loss, and reported in a separate article in the same Annals of Internal Medicine supplement, were excluded.
Data extracted from the studies included sex, age at first and last weight determination, methods for and expression of weight or body mass index (BMI) change, duration of weight change and of mortality follow-up periods, temporal separation between weight change and mortality assessment periods, number of deaths, smoking status and other confounders, and exclusion criteria.
13 studies that included 62 643 participants more than 17 years old and 7511 deaths (2 studies did not report the number of deaths) were selected. 7 populations from the United States and 4 from Europe were represented. All studies included men and 7 studies included women. 9 studies adjusted for smoking in their analysis and 1 study excluded smokers. The weight-change period was at least 4 years, and the mortality assessment period was at least 8 years. The lowest all-cause mortality category was associated with mild or moderate weight gain in men in 10 studies and in women in 4 studies, with no change in weight in men in 2 studies, with mild or moderate weight loss in men in 1 study and in women in 1 study, and mortality was not influenced by weight change in 1 study of men and women. Mild-to-moderate weight loss was associated with high mortality in 10 studies of men and 3 studies of women, with low mortality in 1 study of men, and had no effect on mortality in 1 study of men and 4 studies of women.
A mild or moderate interval weight gain was generally associated with the lowest all-cause mortality. Weight loss was generally associated with the highest mortality. Somewhat higher mortality was also typically present in those with the greatest weight gain.
Source of funding: Not stated.
For article reprint: Dr. R. Andres, Gerontology Research Center, 4940 Eastern Avenue, Baltimore, MD 21224, USA. FAX 410-558-8113.
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