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17.05.2011

Calorie burning reduces mortality in elderly

The more energy people in their seventies expend on physical activities, the less likely they are to die. According to a study done by the American National Institute on Aging, elderly people who burn high amounts of calories because they take daily exercise are twice less likely to die than elderly people who do not burn many calories.

Exercise & life span
Physical activity extends life span, certainly if you do both high and moderate intensity exercise. People who get a lot of exercise have longer telomeres – as do people with a higher VO2max – and the likelihood of dying increases with every hour spent sitting daily.

The protective mechanism that movement provides works in a complex way. Movement reduces the chance of dying from chronic diseases such as diabetes-2, cancer and heart and vascular disease. A partial explanation of the positive effect of movement is that it stimulates the activity of more detoxifying enzymes. A recent theory suggests that developed muscle mass results in considerable emissions of anti-inflammatory and life-extending signal substances. That's why muscular strength is believed to protect against cancer and why strong men are thought to live longer.

Study
Theory is all very well, but facts are useful too. So the researchers gathered data on 302 "high-functioning, community-dwelling older adults" aged between 70 and 82 years. The researchers used questionnaires to find out how much daily exercise the septuagenarians got and how many calories they burned as a result. They then monitored their subjects for 6 years.

Results
During that period 55 of the elderly people died. The more calories the elderly subjects burned, the lower their chance of dying. The figure below shows that, of the subjects who expended less than 521 calories on physical exercise, 25 percent died during the research period. Of the subjects who burned over 770 calories through exercise only 12 percent died.

The table above shows that, for every 287 calories that the septuagenarians expended on physical activity, their chance of dying declined by 30 percent. The researchers corrected their figures for every variable they could think of: "age, sex, race, weight, height, percentage of body fat, sleep duration, self-rated health, education, smoking status and history, cardiovascular disease, lung disease, diabetes, hip or knee osteoarthritis, osteoporosis, cancer, and depression."

Conclusion
"Efforts to increase or maintain free-living activity energy expenditure will likely improve the health of older adults", the researchers conclude.

It's possible that the figures underestimate the life-extending effect of physical exercise. It was not by doing sport or walking that the active subjects burned more calories, but by doing paid work. Apparently the septuagenarians burned more calories at work than during their free time.

Source:
JAMA. 2006 Jul 12;296(2):171-9.

More:
Raise your VO2max to delay ageing 18.04.2011
The rejuvenating effect of 45 minutes' running every day: animal study 28.01.2011
Physical exercise delays molecular aging by ten years 25.12.2008