Among 44,876 middle-aged and older women, we observed that weight cycling was not strongly related to mortality. Women who intentionally lost weight multiple times (i.e., weight cyclers) gained more weight than their peers, but after controlling for their weight gains and other confounding variables, weight cycling was not predictive of cardiovascular or total mortality. Among never smokers there was no suggestion of an increased risk of total mortality in weight cyclers.
Few studies have collected information on intentional weight losses, repeated weight losses, or weight cycles (gain-loss or loss-gain). In general, intentional weight losses have been found to be protective or unrelated to risk. 10,12, 19
After taking into account preexisting conditions, Wannamethee et al. did not observe evidence of an increase in risk for all-cause or cardiovascular death among men who lost and then gained weight. A similar lack of association was observed by Lissner et al. 33
among men in the Baltimore Aging Study. However, Folsom et al. observed that among women in the Iowa Women's Study, weight large cycles (weight losses of ≥ 10% of weight followed by gains of ≥ 10% of weight or vice versa) were associated with increased risk of all-cause mortality. Similarly, Dyer et al. observed that weight fluctuations were predictive of cardiovascular mortality among men in the Chicago Western Electric Company Study34
and Rzehak et al. observed that there was an 86% increase in risk of death among weight fluctuators in the ERFORT male cohort study. In addition, in the Framingham Heart Study, weight variability was predictive of all-cause mortality among both men and women.2
Unfortunately, intentionality of the weight losses was not taken into account in these studies.
Weight loss is more complicated to study in the elderly since it is common for older adults to lose muscle mass while maintaining their weight, or to maintain their weight, but have their body fat become more centrally located. Moreover, since the background death rate is considerably higher among older adults, the relative risks tend to be smaller among adults in their 70s, 80s, and 90s.35
Nevertheless a few studies have examined the effect of weight loss among the elderly, but none have assessed the association of intentional weight loss with mortality. In one of these studies, Wedick et al.36
followed 1,801 elderly men and women over 12 years. They observed that weight loss, but not weight gain, was predictive of total mortality. Among the men and women who reported a history of dieting, which could be viewed as a surrogate marker of intentional weight loss, weight loss was not predictive of mortality among the diabetic women or the non-diabetic men and women. Whereas, Newman et al.22
observed that among 4,714 elderly adults in the United States, weight loss was associated with having a higher BMI, and higher prevalence of heart disease, stroke, hypertension, and smoking at baseline. Weight loss was a significant predictor of mortality, but dieting did not have an independent association with mortality, which implies that intentional weight loss did not have an adverse impact on mortality. In our study, we did not find evidence that repeated intentional weight losses of any magnitude were predictive of mortality among middle aged or older women. The results were not materially changed when we limited the sample to women no more than 70 years of age, which suggests that the main results were not biased downwards due to the age of the sample over the follow-up.
One limitation to our analysis is that we did not collect information on amounts of weight lost unintentionally, so we were unable to estimate the independent associations of both intentional and unintentional weight losses. Moreover, we did not have information on amount regained from each of the intentional weight loss episodes or from unintentional weight losses, so our net weight change variable may have some measurement error. Despite these limitations, there are many strengths to the current study. First, this is the largest prospective investigation of weight cycling and mortality among a relatively healthy population of adult women. In the Iowa Women's Study, another cohort where information on intentional weight losses was collected, women were asked to recall weight changes made many years in the past,37
thus increasing the chance for misclassification. Moreover, in the current analyses we were able to update information on confounders over the ten years of follow-up. In addition, unlike the excellent studies of Gregg et al. 10, 20
and Williamson et al.,12, 19, 21
which studied the association between voluntary weight loss and mortality, the present study was the first large study to investigate prospectively the association between weight cycling due to repeated intentional weight losses and mortality.
Our results suggest that repeated intentional weight losses are not associated with mortality among middle aged or older women. Thus, earlier reports of weight loss being predictive of higher death rate may be due failing to distinguish intentional from unintentional weight loss, as well as confounding by weight regain. Given that approximately 68% of middle aged and older American women are overweight or obese, it is encouraging to find that repeated voluntary weight losses are not associated with adverse health consequences since many of these women would be at lower risk if they were able to maintain a lower BMI.