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