Abstract
Background and aimsIncreased body mass index (BMI = weight/height2; kg/m2) and weight gain is associated with increased mortality, wherefore weight loss and avoided weight gain should be followed by lower mortality. This is achieved in clinical settings, but in the general population weight loss appears associated with increased mortality, possibly related to the struggles with body weight control (BWC). We investigated whether attitudes to and experiences with BWC in combination with recent changes in body weight influenced long-term mortality among normal weight and overweight individuals.Population and methodsThe study population included 6,740 individuals attending the 3rd cycle in 1991–94 of the Copenhagen City Heart Study, providing information on BMI, educational level, health behaviours, well-being, weight half-a-year earlier, and answers to four BWC questions about caring for body weight, assumed benefit of weight loss, current and past slimming experiences. Participants reporting previous unintended weight loss (> 4 kg during one year) were excluded. Cox regression models estimated the associations of prior changes in BMI and responses to the BWC questions with approximately 22 years all-cause mortality with age as ‘time scale’. Participants with normal weight (BMI < 25.0 kg/m2) and overweight (BMI ≥ 25.0 kg/m2) were analysed separately, and stratified by gender and educational level, health behaviours and well-being as co-variables.ResultsCompared with stable weight, weight loss was associated with significantly increased mortality in the normal weight group, but not in the overweight group, and weight gain was not significantly associated with mortality in either group. Participants with normal weight who claimed that it would be good for their health to lose weight or that they were currently trying to lose weight had significantly higher mortality than those denying it. There were no other significant associations with the responses to the BWC questions in either the normal weight or the overweight group. When combining the responses to the BWC questions with the weight changes, using the weight change as either a continuous or categorical variable, there were no significant interaction in their relation to mortality in either the normal weight or the overweight group.ConclusionAttitudes to and experiences with BWC did not notably modify the association of changes in body weight with mortality in either people with normal weight or people with overweight.
Highlights
Increased body mass index (BMI = weight/height2; kg/m2) as well as body weight gain is associated with increased mortality [1,2,3,4], so weight loss among people with overweight and avoidance of further weight gain is expected to be associated with lower mortality
The studies have so far not identified increased risk of particular diseases as causes of the increased mortality, but it appears that the accompanying reduction of the lean body mass drives the association [13, 14]. This may outweigh the possible, but limited benefits from reducing the fat mass in people without obesity and reduce the benefits of weight loss in people with obesity, after planned treatment aiming at weight loss [15]
In this study of individuals from the general population, who reported that they had not suffered from health problems that in the past have induced unintentional weight loss of at least 4 kg during a year, the normal weight people who lost weight experienced a 24% excess mortality compared to those keeping their weight stable, whereas those gaining weight during the past half year did not show excess mortality
Summary
Underlying undiagnosed diseases or hazardous behaviours both inducing weight loss and enhancing mortality may confound the association, studies have so far not found indications of that kind of otherwise obvious risk of confounding [11, 12]. The studies have so far not identified increased risk of particular diseases as causes of the increased mortality, but it appears that the accompanying reduction of the lean body mass drives the association [13, 14] This may outweigh the possible, but limited benefits from reducing the fat mass in people without obesity and reduce the benefits of weight loss in people with obesity, after planned treatment aiming at weight loss [15]. We investigated whether attitudes to and experiences with BWC in combination with recent changes in body weight influenced long-term mortality among normal weight and overweight individuals
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