PHYSICAL FITNESS, FATNESS AND LIFESPAN

As I said in my previous Blog – “What is physical fitness?” – a recent Mayo Clinic Proceedings editorial discusses the importance of physical fitness and longevity and concludes that high levels of fitness increase lifespan regardless of levels of adiposity¹. That means that the fitter you are the longer you may expect to live, even though you are overweight.

Obesity and life expectancy

Obesity is not a disease but it is a powerful risk factor for a number of dangerous illnesses which include such age-related conditions as type-2 diabetes, dementia, hypertension, heart attacks, strokes, and several varieties of cancer. Mortality rate increases by 30% for every increment of five above a body mass index (BMI – see glossary) of 25.

The risks are much greater for men than for women at all levels of obesity. About one in seven premature deaths in Europe is due to being overweight (BMI between 25 and 30) or obese (BMI more than 30). Overweight people lose on average one year of life and obese people lose about three years of life. There is a U-shaped curve which describes the relationship between BMI and mortality – the lowest mortality being at about 22. Lower BMIs are associated with increased mortality as too are higher BMIs. It is presumed that thin people include those who are thin because they suffer ill health or display unhealthy behaviour such as smoking.

Physical fitness and life expectancy

Numerous studies have confirmed the relationship between physical fitness and life expectancy – indeed physical fitness in the middle aged is the best predictor bar none of what age you will achieve, and that includes blood cholesterol, presence of obesity, high blood pressure or diabetes or even pre-existent heart disease and cigarette smoking. Only increasing age is a better predictor of how many years are left to you. The reduction in mortality in the fit compared with the unfit is largely due to lower rates of cardiovascular disease and cancer.

The effects of fitness and fatness on life expectancy

The Mayo Clinic paper reports on a study of the effects of fitness on life expectancy at different levels of body weight. It found that for those with a high level of fitness, life expectancy was fairly similar across a spectrum of BMI – so if you are overweight or obese your life expectancy is dependent on how fit you are rather on how fat you are. The highest mortality was seen in unfit people with a low BMI. The differences were considerable – fit participants had an expected lifespan of 86 for women and 85 for men. For unfit thin people the figures were 72 and 65 years respectively.

Fitness and obesity

The Mayo Clinic finding is that physical fitness can alleviate some of these complications of being overweight or obese. The bad news is that obese people almost always have low levels of fitness. Fit obese people are rarities – hardly surprising because getting fit almost always involves losing weight!

doi.org.10.1016/j.mayocp.2019.0