Inactivity – a public health problem
- Facts about inactivity
- Facts about obesity
- Obesity and exercise
- Inactivity risks and obesity
- Recommendations for physical activity
- Activity levels and health
- High-intensity exercise
It is well known that obesity is on the rise, both in Norway and the world at large, and with it, the incidence of a variety of lifestyle-related diseases.1 The lack of physical activity plays an important part in many of these diseases. According to the Norwegian 2002 Public Health Report, physical inactivity can be considered an independent risk factor of the same magnitude as hypertension, smoking, and an unhealthy cholesterol profile.2
Inactivity increases the risk of both cardiovascular disease and obesity, and individuals with low activity levels are 50 percent more likely to be overweight.3 Inactivity is responsible for many needless deaths every year, and can be considered one of the silent killers of our time. Although it is unknown exactly how many people die of inactivity in Norway every year, the U.S. Department of Health and Human Services believes that 30 percent of all American deaths are cause by inactivity, making it the nation's most common cause of death.4
If one assumes a similar percentage in Norway, where the total number of deaths in 2010 was 41,500 people,5 the numbers are chilling. Should the Norwegian percentage be lower, for example "only" 20-25%, this still corresponds to almost 10,000 deaths per year, or one person every hour. At the full 30%, the rate would be one death every 42 minutes, or 12,450 Norwegians per year.
The exact mechanism of how inactivity causes disease remains unknown, but in a study where healthy young people transitioned from an active to an inactive lifestyle, researchers found an increase in abdominal fat and a reduced insulin response after only a fortnight. Both of these are serious concerns in metabolic syndrome. Their conclusion was that chronic inactivity – that is, the lack of physical activity over an extended period of time – led to a permissive environment where various lifestyle-related diseases could arise more easily.6 The deaths from inactivity are particularly sad since they easily could be prevented through regular physical activity.
Obesity is no longer a problem exclusive to developed countries – in fact, on a global basis, overweight and obesity kill more people than underweight. In 2010, the World Health Organization (WHO) reported that 65 percent of the world's population lived in countries where obesity was a more frequent cause of death than underweight. WHO-estimates from 2008 asserted that there were approximately 1.4 billion overweight adults, and globally, more than 1 of 10 adults had a BMI corresponding to obesity. In 2012 there were additionally some 40 million overweight children under five years old, of whom only 10 million lived in wealthy countries; the other 30 million being from developing countries.7
The international measure of obesity is by Body Mass Index (BMI). A normal BMI lies between 20-25, overweight goes from 25-29, and obesity of increasing degrees of severity at a BMI greater than 30.
It would be natural to assume that the rise of obesity is a result of people exercising less, however this is not actually the case. CERG-researcher Trine Moholdt explains:
"According to the Nord-Trøndelag health study (HUNT), it appears that people are exercising more now than they did in the mid-1980s. Yet over the course of the same timespan, we've gotten substantially fatter. Average BMI, a measure of the relationship between height and weight, has increased significantly in Nord-Trøndelag in the last couple decades. Now, as many as three out of four men, and 60 percent of women are either overweight or obese. The largest increases are seen in the youngest age groups. In spite of this, people in Nord-Trøndelag are reporting that they exercise more frequently than they used to, and for longer periods of time. Additionally, many have increased the intensity of their workouts.
How can this be? There are multiple explanations. Perhaps people are eating more than before, but are unable to meet the increased caloric intake with sufficient exercise. Yet this is not a probable explanation. It's more likely that people are inactive more of the time when they aren't working out. A couple hours of exercise each week is inadequate if the remainder is spent at rest. Daily activity levels have probably declined significantly over the past years. We spend too much time in front of a screen or in our cars. This is a real challenge for the future!" 8 9
Inactivity is not just a problem because it makes people fatter, which in turn causes more disease from obesity. In addition, researchers have also found an inverse relationship between physical activity and all-cause mortality independent of adiposity (i.e. fatness).This relationship remains regardless of whether test subjects are normal, overweight or obese.10
- An increased lifespan
- Significantly reduced risk of developing cardiovascular disease
- Significantly reduced risk of developing type 2 diabetes
- Reduced risk of high blood pressure
- Various reductions of risk for cancers, depending on the type of cancer
- Reduced risk of skeletomuscular disease, osteoporosis and biomechanical diseases
- Reduced risk of mental illness11
The Norwegian Directorate of Health recommends:
They note that it is the total amount of exercise that matters, meaning that the target of 3.5 hours per week can be reached with fewer, longer bouts of exercise, or by dividing the physical activity into multiple shorter bouts throughout the day.13
This corresponds to international recommendations for physical activity. According to the U.S. Department of Health and Human Services:
Essentially, this means that people who exercise regularly live longer, so it's worthwhile to stay fit. At the same time, people who exercise less than the recommended amount still benefit significantly from physical activity. CERG research and other studies also show that it is possible to increase physical fitness and improve cardiac health with less than half an hour per day – especially if you choose high-intensity training over a light jog, because…
Although 2.5-3.5 hours per week might not sound like much, a large segment of the population still find it overwhelming. In an American study where physical fitness was measured by accelerometer, rather than determined by surveys, less than 5 percent of adults met the recommended half hour every day.15
Inactivity carries clear health risks, but the good news is that there is a significant health benefit from just a little physical activity, compared to none at all.16 One of our newer studies showed that for moderately trained people, 1x4 interval training might have the same impact on cardiac health and fitness as 4x4 training. This is a good example of how just a few minutes can make a big difference.
Moreover, another CERG-study of patients with metabolic syndrome showed that the greatest reduction in mortality was found in individuals who maintained a low level of physical activity, compared to none at all. Although the reduction in mortality was even greater in people who exercised more, it is important to recognize that every minute counts.
Recommended physical activity levels do not represent a magic threshold above which further activity is irrelevant, rather the message should be that some exercise is good, but more is better.17 The U.S. Department of Health and Human Services found that the mortality in people who exercised 1.5 hours a week was 20% lower compared to people who exercised less than half an hour per week. At the same time, it was necessary to exercise for approximately 7 hours per week in order for the reduction in mortality to double to 40%.18 Clearly the relationship is non-linear, and research shows that the risk reduction plateaus at more than 100 minutes of exercise per day.19
The intensity of the physical activity also matters. Research has show that high-intensity training reduces the risk of disease more than physical activity of a lower intensity.20 Some studies have also been able to show that this risk reduction actually stems from the increased intensity, not just the higher energy expenditure from high-intensity exercise.21 This means that while high-energy workouts are good for you, high-intensity workouts are even better.
Moreover, a 2011 study showed that high-intensity interval training was perceived to be more enjoyable than continuous moderate exercise, and concluded that this could improve exercise adherence.22 One should think of exercise as having an expiration date – the benefits cannot be stored for later, so if a little interval training sounds more appealing than a relaxing run, you should jump at the opportunity.
High-intensity exercise is definitely a research focus at CERG, and we recommend 4x4 interval training as part of your personal fitness plan. We have compared high-intensity interval training to continuous moderate exercise in multiple contexts, and found that aerobic interval training more effectively improves physical fitness. For instance, we showed that myocardial infarction patients recover better with interval training compared to continuous moderate exercise both in the short and longer terms. Inactivity kills, so be sure to exercise regularly – for example by 4x4 interval training!
To read more about publications from CERG, please see our research news. To learn more about 4x4 interval training, please see our general exercise advice, answers to common questions, and a 7-week fitness program that you can use to get fit fast.
- WHO – Obesity and Overweight (return to 1)
- Helse- og omsorgsdepartementet – Folkehelserapporten 2002 (return to 2)
- Hansen, Anderssen and Kolle – Idrettsmedisinsk høstkongress 2011 (return to 3)
- Booth and Hargreaves – Pubmed (return to 4)
- Statistisk sentralbyrå (return to 5)
- Thyfault and Krogh-Madsen (return to 6)
- WHO – Obesity and Overweight (return to 7)
- Trine Moholdt – CERG blog (return to 8)
- Moholdt and Aspenes – Idrettsmedisinsk høstkongress 2011 (return to 9)
- U.S. Department of Health & Human Services – adiposity (return to 10)
- Helse- og omsorgsdepartementet – Folkehelserapporten 2002 (return to 11)
- Helsedirektoratet – Generelle anbefalinger om fysisk aktivitet (return to 12)
- Helsedirektoratet – Anbefalinger for fysisk aktivitet (return to 13)
- U.S. Department of Health & Human Services – minimum (return to 14)
- Troiano et al. – PubMed (return to 15)
- Helse- og omsorgsdepartementet – Folkehelserapporten 2002 (return to 16)
- Nigam and Juneau (return to 17)
- U.S. Department of Health & Human Services – dose-shape (return to 18)
- Wen et al. – PubMed (return to 19)
- Wen et al. – PubMed (return to 20)
- U.S. Department of Health & Human Services – dose-intensity (return to 21)
- Bartlett et al. – PubMed (return to 22)
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NTNU, Fakultet for medisin og helsevitenskap
Institutt for sirkulasjon og bildediagnostikk
St. Olavs Hospital
Prinsesse Kristinas gt. 3
Akutten og Hjerte-lunge-senteret, 3. etg.