The Damage Done to Health and Life Span: Obesity and Inactivity are by Some Measures Worse than Smoking

From the perspective of health and longevity, the three most damaging things that people commonly do to themselves are (a) take up smoking, (b) lead a sedentary lifestyle, and (c) become obese. A sizable percentage of the population in the wealthier regions of the world falls into at least one of those buckets. The result for near all such people is higher lifetime medical expenses, greater ill health, and a shorter life. The damage done scales by the degree to which an individual smokes, fails to exercise, or puts on weight: there is plenty of evidence to show that even a little additional weight is harmful in the long term, for example. I think that by now the consequences of smoking are widely appreciated, but awareness that choosing to lead a sedentary lifestyle or to carry a lot of excess fat tissue is just as bad? That has yet to spread to the same degree. The open access paper I'll point out today is one of those that finds the losses of life or health caused by obesity and inactivity to be greater than the losses caused by smoking.

How do these choices produce damage that looks a lot like accelerated aging, increasing the incidence of age-related disease, and causing higher mortality rates? I shouldn't have to dwell on the results of smoking for this audience: greatly increased inflammation; particulate matter in the lungs; increased risk of cancers, fibrosis, and cardiovascular disease; and so on. How is it that inactivity and obesity can achieve the same level of harm? In the case of obesity, visceral fat tissue is the driver of damage. It is a very active tissue, producing significant changes in the operation of metabolism and the organs it wraps: metabolic syndrome, type 2 diabetes, and so forth. Visceral fat tissue also produces higher levels of chronic inflammation throughout the body through its interaction with immune cells, and inflammation speeds the development of cardiovascular disease, dementia, and most of the other ultimately fatal age-related diseases. In the case of a sedentary lifestyle, it is easier to look through the literature to find the gains produced by exercise rather than searching for the losses produced by a lack of exercise. Exercise slows the stiffening of blood vessels that leads to cardiovascular disease, increases cellular maintenance activities, improves the immune system by culling unwanted cells, and much more. Like calorie restriction, exercise changes almost every measure of metabolism for the better.

Thus we have this paper, which like so many others catalogs the damage that people inflict upon themselves through poor choices. One day, probably later in this century, none of this will much matter, because medical science will be able to rescue everyone from the consequences of such poor choices - and then add decades of additional healthy life on top of that, by addressing the root causes of aging. We are not there yet, however, and in a world in which progress is rapid, every additional few years of expected life span might make the difference between dying too soon and living to benefit from the first effective rejuvenation therapies. Far and away the most reliable way to add those years today is to take better care of your long-term health.

Smoking, physical inactivity and obesity as predictors of healthy and disease-free life expectancy between ages 50 and 75: a multicohort study

A study based on data from 11 European countries estimated that 60% of deaths from all causes could be attributed to behaviour-related risk factors. Furthermore, the importance of health behaviours for the prevention of chronic diseases, such as type 2 diabetes, coronary heart disease and cancer, is widely acknowledged. Smoking, physical inactivity and obesity are among the top 10 behaviour-related risk factors for burden of diseases in developed countries, and they have also been shown to be associated with shorter health expectancy and life expectancy (LE). The cumulative impact of multiple behaviour-related risk factors on health expectancy is of interest because studies show that people who engage in multiple risk behaviours have higher mortality, increased risk of chronic diseases and poor cognitive and lower physical functioning compared with people who have no or only one behaviour-related risk factor.

Previous studies have estimated healthy years and disability-free years separately for smoking and obesity. In addition, there are at least two large studies that used information on past trends or current levels of obesity and smoking to estimate the combined effect of obesity and smoking on quality-adjusted LE and disability-free LE. Of the two risk factors, obesity appeared to be the main driver for shortened disability-free LE. However, neither of these studies considered low physical activity among the risk factors. This is a limitation, as regular physical activity is known to be associated with reduced risk of several chronic diseases, better physical and cognitive functioning in old age and higher longevity. To address some of these limitations, we examined the extent to which the co-occurrence of three modifiable behaviour-related risk factors, namely smoking, physical inactivity and obesity, predicted healthy LE and chronic disease-free LE in a large dataset of older men and women in England, Finland, France and Sweden. In addition, we estimated the associations of individual risk factors with these outcomes.

Compared with men and women with at least two of the smoking, physical inactivity and obesity risk factors, people with no risk factors could expect to live on average 8 years longer in good health and 6 years longer free of chronic diseases between the ages of 50 and 75 years. The reduction in healthy and chronic disease-free LE was greater for those with multiple behaviour-related risk factors than those with a single risk factor, a finding observed in all four cohorts. Of the individual behaviour-related risk factors, physical inactivity was associated with the greatest reduction in healthy years and obesity with greatest reduction in chronic disease-free years. In all cohorts of this study, healthy LE was longer than chronic disease-free LE. This has also been observed in other studies using multiple types of health indicators to calculate health expectancy. This is expected because suboptimal self-rated health is a holistic measure and it captures a wider range of health-related phenomena beyond chronic disease. Therefore, individuals with chronic diseases may consider their health good if the disease does not hamper everyday life.


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