Thursday, June 28, 2012

Is sitting down bad for you?

Chicken and egg again.   Many of the people who sat down a lot may have done so because they were in poor health anyway

Note that even if the theory below is correct, sitting down could have benefits as well as disadvantages.  It may lead to less wear and tear on the joints, for instance

You may want to sit down before you read this - but best not to. Study after study has shown not only that being inactive is bad for your fitness but also that sitting for long periods each day may shorten your lifespan.

In fact sitting for more than six hours a day can make you up to 40 per cent likelier to die within 15 years than someone who sits less than three hours a day.

Basically, those who sit for longer periods of time aren't getting the consistent and continual physical activity needed to maintain a healthy body.

The facts about the effects of sitting for long periods are confronting in the modern world, which seems designed to encourage or even force workers and students to sit. The hard truth is:

People with jobs that require sitting tend to have twice the rate of cardiovascular disease of people who mostly stand on the job.

After two hours of sitting, good cholesterol drops 20 per cent.

A study published in the journal Medicine and Science in Sports and Exercise showed that men who spent more than 23 hours a week watching television and sitting in their cars (as passengers or as drivers) had a 64 per cent greater chance of dying from heart disease than those who sat for 11 hours a week or less.

As soon as you sit down, electrical activity in the leg muscles shuts off and calorie burning drops to one a minute.

If you have a desk job or spend a lot of time at the computer, proper chair height, distance from your desk, arm and wrist rests and degree of bend of the arms and legs are important. Sitting with the feet or lower legs under your chair for example, amounts to a contraction of the back of the thigh (hamstrings). Repeated shortening of these muscles results in greater tightness and lack of flexibility, which in turn can create problems with the lower back.

The muscles that are responsible for lifting the legs, as with walking or climbing stairs, are called hip flexors. With excessive sitting, these muscles react in the same way as the hamstrings, shorter and tighter. Postural changes can occur over time related to leaning forward, slouching and rounding the back, crossing the legs etc, taking its toll on the hips, spine and shoulders.

Even if you have a desk job, there are things you can do to help avoid problems related to too much sitting. These include:

When the phone rings, instead of staying seated, make a habit of walking while having the conversation.

If your building has stairs, take them instead of using the lift whenever possible.

Wear a pedometer throughout the day. This can be a real eye-opener as to how inactive you may be. Aim for the recommended 10,000 steps a day.

Use work breaks to get up and move.

Set a goal of standing up and stretching once an hour. Regular stretching relieves stress and can help ease tightness that might otherwise get the better of you.

Sedentary behaviors increase risk of cardiovascular disease mortality in men

By Warren TY et al.


PURPOSE:  The purpose of this study was to examine the relationship between two sedentary behaviors (riding in a car and watching TV) and cardiovascular disease (CVD) mortality in men in the Aerobics Center Longitudinal Study.

METHODS:  Participants were 7744 men (20-89 yr) initially free of CVD who returned a mail-back survey during 1982. Time spent watching TV and time spent riding in a car were reported. Mortality data were ascertained through the National Death Index until December 31, 2003. Cox regression analysis quantified the association between sedentary behaviors (hours per week watching TV, hours per week riding in a car, and total hours per week in these two behaviors) and CVD mortality rates.

RESULTS:  Three hundred and seventy-seven CVD deaths occurred during 21 yr of follow-up. After age adjustment, time riding in a car and combined time spent in these two sedentary behaviors were positively (P(trend) < 0.001) associated with CVD death. Men who reported >10 h x wk(-1) riding in a car or >23 h x wk(-1) of combined sedentary behavior had 82% and 64% greater risk of dying from CVD than those who reported <4 or <11 h x wk(-1), respectively. The pattern of the association did not materially change after multivariate adjustment. Regardless of the amount of sedentary activity reported by these men, being older, having normal weight, being normotensive, and being physically active were associated with a reduced risk of CVD death.

CONCLUSION:  In men, riding in a car and combined time spent in these two sedentary behaviors were significant CVD mortality predictors. In addition, high levels of physical activity were related to notably lower rates of CVD death even in the presence of high levels of sedentary behavior. Health promotion efforts targeting physically inactive men should emphasize both reducing sedentary activity and increasing regular physical activity for optimal cardiovascular health.

Med Sci Sports Exerc. 2010 May;42(5):879-85.

Popular low-fat diets 'will not help keep the weight off and are bad for your body', claims study

The diet merry-go-round goes on and on

A new study claims that choosing the right diet to match your body's own biology is key to keeping the pounds off.

The popular low-fat diets may not be very good in terms of keeping the weight off, as well as not being good for your health, according to the study, led by the New Balance Foundation Obesity Prevention Center Boston Children’s Hospital.

The study found that diets that reduce the surge in blood sugar after a meal - either low-glycemic index or very-low carbohydrate – may be preferable to a low-fat diet for those trying to achieve lasting weight loss.

Furthermore, the study finds that the low-glycemic index diet had similar benefits to the very low-carb diet without the negative effects of stress and inflammation as seen by participants consuming the very low-carb diet.

The team said that, while weight re-gain is often attributed to a decline in motivation or adherence to diet and exercise, but biology also plays an important role.

After weight loss, the rate at which people burn calories (known as energy expenditure) decreases, reflecting slower metabolism. Lower energy expenditure adds to the difficulty of weight maintenance and helps explain why people tend to re-gain lost weight.

Prior research by Cara Ebbeling, PHD, and David Ludwig, MD, has shown the advantages of a low glycemic load diet for weight loss and diabetes prevention, but the effects of these diets during weight loss maintenance has not been well studied.

Research shows that only one in six overweight people will maintain even 10 percent of their weight loss long-term.

The study suggests that a low-glycemic load diet is more effective than conventional approaches at burning calories (and keeping energy expenditure) at a higher rate after weight loss.

'We’ve found that, contrary to nutritional dogma, all calories are not created equal,' says Ludwig, who is also director of the Optimal Weight for Life Clinic at Boston Children’s Hospital.

He said: 'Total calories burned plummeted by 300 calories on the low fat diet compared to the low carbohydrate diet, which would equal the number of calories typically burned in an hour of moderate-intensity physical activity.'

Each of the study’s 21 adult participants (ages 18-40) first had to lose 10 to 15 percent of their body weight, and after weight stabilisation they completed all three of the following diets in random order, each for four weeks at a time.

The randomised crossover design allowed for observation of how each diet affected all participants, regardless of the order in which they were consumed:

 *   A low-fat diet,which reduces dietary fat and emphasises whole-grain products and a variety of fruits and vegetables, comprised of 60 percent of daily calories from carbohydrates, 20 percent from fat and 20 percent from protein.

  *  A low-glycemic index diet made up of minimally processed grains, vegetables, healthy fats, legumes and fruits, with 40 percent of daily calories from carbohydrates, 40 percent from fat and 20 percent from protein. Low glycemic index carbohydrates digest slowly, helping to keep blood sugar and hormones stable after the meal.

 *   A low-carbohydrate diet, modeled after the Atkins diet, comprised of 10 percent of daily calories from carbohydrates, 60 percent from fat and 30 percent from protein.

The study used state-of-the-art methods, such as stable isotopes to measure participants’ total energy expenditure, as they followed each diet.

Each of the three diets fell within the normal healthy range of 10 to 35 percent of daily calories from protein. The very low-carbohydrate diet produced the greatest improvements in metabolism, but with an important caveat: This diet increased participants’ cortisol levels, which can lead to insulin resistance and cardiovascular disease.

The very low carbohydrate diet also raised C-reactive protein levels, which may also increase risk of cardiovascular disease.

Though a low-fat diet is traditionally recommended by the U.S. Government and Heart Association, it caused the greatest decrease in energy expenditure, an unhealthy lipid pattern and insulin resistance.

'In addition to the benefits noted in this study, we believe that low-glycemic-index diets are easier to stick to on a day-to-day basis, compared to low-carb and low-fat diets, which many people find limiting,' said Ebbeling.

'Unlike low-fat and very- low carbohydrate diets, a low-glycemic-index diet doesn’t eliminate entire classes of food, likely making it easier to follow and more sustainable.'


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