Tag Archives: health

Sedentary Lifestyle? Exercise Isn’t Helping

A somewhat sedentary lifestyle combined with regular exercise is turning us into what physiologists are calling ‘active couch potatoes’–and that exercise, no matter how vigourous, doesn’t appear to be counteracting the negative effects of that sedentary lifestyle.

In rats, this lifestyle was found to produce “unhealthy cellular changes in their muscles” and increase insulin resistance and fatty acid levels in their blood. In conclusion: a mostly sedentary lifestyle is bad for us, regardless of exercise habits.

[Studies have shown] that, to no one’s surprise, the men who sat the most had the greatest risk of heart problems. Men who spent more than 23 hours a week watching TV and sitting in their cars (as passengers or as drivers) had a 64 percent greater chance of dying from heart disease than those who sat for 11 hours a week or less. What was unexpected was that many of the men who sat long hours and developed heart problems also exercised. Quite a few of them said they did so regularly and led active lifestyles. The men worked out, then sat in cars and in front of televisions for hours, and their risk of heart disease soared, despite the exercise. Their workouts did not counteract the ill effects of sitting. […]

Decades ago, before the advent of computers, plasma TVs and Roombas, people spent more time completing ‘light-intensity activities’ […] Nowadays, few of us accumulate much light-intensity activity. We’ve replaced those hours with sitting.

The physiological consequences are only slowly being untangled. […] Scientists believe the changes are caused by a lack of muscular contractions. If you sit for long hours, you experience no ‘isometric contraction of the antigravity (postural) muscles’. […] Your muscles, unused for hours at a time, change in subtle fashion, and as a result, your risk for heart disease, diabetes and other diseases can rise.

via Waxy

Sweetness and the Problem with Diet Sodas

The link between the sweetness of a food and its caloric content may be a trait that our bodies have evolved to recognise. By disrupting what could be a “fundamental homeostatic, physiological process” by using artificial sweeteners, we could be promoting obesity.

That’s the conclusion Jonah Lehrer draws from a study that looks at how sweet tastes may be used to regulate our caloric intake and the adverse effects of diet sodas.

Adult male Sprague-Dawley rats were given differential experience with a sweet taste that either predicted increased caloric content (glucose) or did not predict increased calories (saccharin). We found that reducing the correlation between sweet taste and the caloric content of foods using artificial sweeteners in rats resulted in increased caloric intake, increased body weight, and increased adiposity, as well as diminished caloric compensation and blunted thermic responses to sweet-tasting diets. These results suggest that consumption of products containing artificial sweeteners may lead to increased body weight and obesity by interfering with fundamental homeostatic, physiological processes.

Gradual Sleep Deprivation, Obesity and Cognitive Impairment

By getting less than our required amount of sleep over an extended period of time (two weeks, for example) we are increasing our risk of obesity and impairing our cognitive abilities without even being aware of it.

That’s the conclusion from a short article summarising the surprising effects of gradual sleep deprivation:

Researchers […] restricted volunteers to less than six hours in bed per night for two weeks. The volunteers perceived only a small increase in sleepiness and thought they were functioning relatively normally. However, formal testing showed that their cognitive abilities and reaction times progressively declined [until] they were as impaired as subjects who had been awake continuously for 48 hours.

Moreover, […] too little sleep changes the body’s secretion of some hormones. The changes promote appetite, reduce the sensation of feeling full after a meal, and alter the body’s response to sugar intake—changes that can promote weight gain and increase the risk of developing diabetes. […]

A recent review […] of the large studies that followed people over time agreed that short sleep duration was associated with future weight gain. […] For example, [one study] showed an inverse correlation between sleep duration and obesity in high-school-age students. The shorter the sleep, the higher the likelihood of being overweight, with those getting six to seven hours of sleep more than two and a half times as likely to be overweight as those getting more than eight hours. […]

The good news is that these effects can be reversed by getting an adequate amount of sleep. […] Allowing the study subjects to sleep 10 hours for two consecutive nights returned the hormones to normal levels and lowered hunger and appetite ratings by almost 25 percent.

via @finiteattention

The Evidence on Breastfeeding

In an article the Royal Statistical Society announced as the runner-up in their annual Awards for Statistical Excellence in Journalism, Helen Rumbelow thoroughly investigates the well-debated subject of breastfeeding.

The conclusion of the piece is that much of the evidence in support of breastfeeding is massively misrepresented or inherently flawed.

“The evidence to date suggests it probably doesn’t make much difference if you breastfeed.” […]

“The conclusion is that the evidence we have now is not compelling. It certainly does not justify the rhetoric,” [American academic Joan Wolf] says. The problem with the studies is that it is very hard to separate the benefits of the mother’s milk from the benefits of the kind of mother who chooses to breastfeed. In the UK, for example, the highest class of women are 60 per cent more likely to breastfeed than the lowest, so it is not surprising that research shows that breastfed infants display all the health and educational benefits they were born into. But even if education, class and wealth is taken into account, there is known to be a big difference between the type of mother who follows the advice of her doctor and breastfeeds, and the one that ignores it to give the bottle. In other words, breastfeeding studies could simply be showing what it’s like to grow up in a family that makes an effort to be healthy and responsible, as opposed to anything positive in breast milk.

This is not to say that breastfeeding is not good:

  • Wolf acknowledges that it helps prevent gastrointestinal infections (life-saving in the developing world, generally a mild complaint in the West).
  • Michael Kramer (one of the world’s most authoritative sources of breastfeeding research; advisor to the WHO, Unicef and the Cochrane Library) believes:
    • The evidence is “encouraging” in preventing respiratory problems.
    • The data on helping prevent breast cancer is “solid”.

However:

  • The data on obesity, allergies, asthma, leukaemia, lymphoma, bowel disease, type 1 diabetes, heart disease and blood pressure are “weak” at best.
  • The “highly respected” American Agency for Healthcare Research and Quality (AHRQ) warns that, “because the breastfeeding mothers were self-selecting, ‘one should not infer causality'”.
  • The World Health Organisation’s own research review concluded that gains were “modest” and also warned that “because none of the studies it looked at dealt with the problem of confounding, the results could be explained by the ‘self-selection of breastfeeding mothers'”.

via @TimHarford

The Effectiveness of Social Support on Exercise Goals

Informing our friends and family of our resolutions in hope that the social support will encourage us is an effective tactic–as long as these people ‘check-in’ on our progress at semi-regular intervals.

That’s the conclusion from a study where three groups of people had their exercise goals tracked under one of three conditions: a regular phone call from an exercise instructor, a regular automated call from a machine, and a control group receiving no calls.

The results showed that having to report your progress toward a goal drastically increases the amount of effort undertaken–especially when it’s a human checking-in on your progress.

The caller, whether human or computer, asked the participants to recite the amount of exercise they performed during the past week. Participants were then congratulated on any exercise performed, and asked how the level might be increased in the week ahead. When lapses occurred […] the goal was to impress upon participants the importance of resuming the workout as soon as possible. All questions were designed to encourage rather than to scold.

After 12 months, participants receiving calls from a live person were exercising, as a mean, about 178 minutes a week, above government recommendations for 150 minutes a week. That represented a 78% jump from about 100 minutes a week at the start of the study. Exercise levels for the group receiving computerized calls doubled to 157 minutes a week. A control group of participants, who received no phone calls, exercised 118 minutes a week, up 28% from the study’s start. […]

Some studies by other researchers have suggested that after eight weeks of regular exercising many people can settle into a long-term habit of working out.

The article also cites a study on how meeting in groups to discuss exercising goals (group-counseling) showed a quadrupling of exercise levels after three months and an even greater jump at nine months (long after the group-counseling sessions ended in month three). By contrast, “the exercise level of a control group rose during the study period but at nine months had returned to near-baseline levels”.

via Nudge