The extra benefits of exercise.
In an invited editorial in the British Journal of Sports Medicine accompanying Chuck Ratzlaff’s paper (discussed in Food for Thought), Profs Wendy Brown and Steven Blair remind us that although prevention of weight gain is extremely important for public health, ‘the benefits of physical activity are not restricted to weight-gain prevention or weight control.’ They highlight the extra benefits of participating in exercise and improved fitness, over and above those associated with weight control such as improved cognitive functioning, quality of life and sleep. They also make the point that: ‘in any consideration of the relationships between energy expenditure and health, both fitness and weight need to be considered. While occupational activity may contribute to energy expenditure, for most people, occupational activity is not at a level that will improve fitness. In today’s world, participation in activities that maintain and improve fitness are important for health; being overweight and fit is associated with better health outcomes than being healthy weight and unfit. In our view, exercise remains the best buy in public health.’
Did you know that the average adult spends 90% of their leisure time sitting down? Standing up more often may reduce your chances of dying within three years, even if you are already physically active, a study of more than 200,000 people published in Archives of Internal Medicine shows. The study found that adults who sat 11 or more hours per day had a 40% increased risk of dying in the next three years compared with those who sat for fewer than four hours a day. This was after taking into account their physical activity, weight and health status.
“These results have important public health implications,” said study lead author Dr Hidde van der Ploeg, a senior research fellow at the University of Sydney’s School of Public Health. “That morning walk or trip to the gym is still necessary, but it’s also important to avoid prolonged sitting. Our results suggest the time people spend sitting at home, work and in traffic should be reduced by standing or walking more.”
The results are the first landmark findings to be published from the Sax Institute’s 45 and Up Study, the largest ongoing study of healthy ageing in the Southern Hemisphere. The study’s size and focus on total sitting time make it an important contributor to the growing evidence on the downsides of prolonged sitting.
Why too much sitting is bad for your health.
Researchers at the Baker IDI Heart and Diabetes Institute in Australia who tracked the TV viewing habits of 8800 adults in Australia over 6 years report in Circulation that compared with people who watched less than two hours of television daily, those who watched more than four hours a day had a 46% higher risk of death from all causes and an 80% increased risk for CVD-related death. ‘It’s not the sweaty type of exercise we’re losing,’ says Prof. David Dunstan. ‘It’s the incidental moving around, walking around, standing up and utilizing muscles that doesn’t happen when we’re plunked on a couch in front of a television.’ In fact, the study participants typically reported getting between 30 and 45 minutes of exercise a day. What has happened is that a lot of the normal activities of daily living that involved standing up and moving the muscles in the body have been converted to sitting,’ he said. ‘People don’t move their muscles as much as they used to – consequently the levels of energy expenditure as people go about their lives continue to shrink. For many people, on a daily basis they simply shift from one chair to another – from the chair in the car to the chair in the office to the chair in front of the television. Even if someone has a healthy body weight, sitting for long periods of time still has an unhealthy influence on their blood glucose and blood fats,’ he said. Here are David’s tips for moving more:
- Switch off, stand up and get moving
- Avoid prolonged periods of sitting – whether in front of the TV, a computer screen or on transport. At the very least get up and move once every hour
- Limit your TV viewing to two hours a day
- Use commercial breaks for household chores
- Stand up and move around while answering the telephone
Associate Professor David Dunstan walks the talk and quits the sit: he stands at his desk!
Quit the sit.
‘When we sit, we have muscle “dis-use” – our muscles are essentially “sleeping”. When we’re up and moving, we’re contracting muscles and it appears that these frequent contractions throughout the day are beneficial for helping to regulate the body’s metabolic processes says Prof David Dunstan. ‘The evidence that sitting is hazardous to health is now quite compelling. But for the vast majority of us who work in desk-bound sedentary jobs, our choice to sit appears largely out of our control. This prompted me to ask the question: How ridiculous is it that people now sit longer than they sleep and what, if anything, can be done about sitting for long periods? Current Australian occupational health and safety guidelines recommend desk-bound employees take a break from their computer screen every 30 minutes or so to reduce eye strain. We’d like to see these guidelines extended to encourage workers to take frequent breaks that involve some kind of physical movement.’
Feces fossils lend new insights into connection between Native-Americans, diabetes.
A common theory why Native Americans experience high rates of diabetes is that they possess fat-hoarding ‘thrifty genes’ left over from their ancestors – genes that were required for survival during ancient cycles of feast and famine, but that now contribute to the disease in a modern world of more fatty and sugary/starchy diets. A newly published analysis of fossilised feces from the American Southwest, however, suggests this ‘thrifty gene’ may not have developed because of how often ancient Natives ate. Instead, researchers said, the connection may have come from precisely what they ate.
The research suggests that the hunter-gatherer civilizations of the Southwest lived on a diet very high in fibre, very low in fat and dominated by foods with a low GI. This diet, researchers said, could have been sufficient to give rise to the fat-storing thrifty genes. ‘What we’re saying is we don’t really need to look to feast or famine as a basis for (the genes),’ said Karl Reinhard, professor of forensic sciences at the University of Nebraska-Lincoln’s School of Natural Resources and the study’s lead author. ‘The feast-or-famine scenario long hypothesized to be the pressure for ‘thrifty genes’ isn’t necessary, given the dietary evidence we’ve found.’
Natives have some of the highest rates of Type 2 diabetes of any group and are more than twice as likely to develop the disease as are Caucasians. To fully understand the basis of the high rates, Reinhard said, ‘one has to look at the best dietary data one can find. That comes from coprolites (the official term for fossilised feces). By looking at coprolites, we’re seeing exactly what people ate.’ The coprolites are from Antelope Cave, a deep cavern in northern Arizona where, over several thousands of years, was home to various cultures. That includes the Ancestral Pueblan peoples, who are believed to have lived there seasonally for at least 450 years.
Reinhard and Keith Johnson, an archeologist at California State University, Chico, studied 20 coprolites found in the cave and combined it with analysis from other sites. They found clues to a food regimen dominated by maize and high-fiber seed from sunflowers, wild grasses, pigweed and amaranth. Prickly pear, a desert succulent, was also found repeatedly in the samples. By volume, about three-quarters of the Antelope Cave coprolites were made up of insoluble fiber. The foods also were low on the glycemic index. The analysts’ findings led them to deduce that the nature of the feast, and not necessarily its frequency, was enough to lock the ‘thrifty’ genes in place – and leave modern Natives more susceptible to diabetes as their diets evolved to lower-fibre, higher-GI foods.
Fish oil is not enough on its own.
Fish oil. The flavour of the month. What can’t it do? An animal study published in Am J Physiol Endocrinol shows that the total (‘background’ is the word they use) diet exerts a crucial influence on the ability of fish oil to protect against developing obesity and adipose tissue inflammation. (Evidence has suggested that low-grade chronic inflammation plays a crucial role in the development of obesity related insulin resistance). The authors show that sucrose (which is actually moderate not high GI) counteracts the anti-inflammatory effect of fish oil in adipose tissue and increases obesity development in mice. ‘To summarise’ they write, ‘it cannot be excluded that several additional beneficial effects of fish oil intake might be diminished or completely abrogated by a simultaneous intake of high-GI carbohydrates. If similar effects are found in humans, this is of great concern because the intake of refined sugars from sources such as soft drinks has increased dramatically during the last several decades.’ The bottom line: stick to low GI carbs.