Ein paar Weihnachtsstudien

1. Effectiveness of a brief behavioural intervention to prevent weight gain over the Christmas holiday period: randomised controlled trial

Objective To test the effectiveness of a brief behavioural intervention to prevent weight gain over the Christmas holiday period.

Design Two group, double blinded randomised controlled trial.

Setting Recruitment from workplaces, social media platforms, and schools pre-Christmas 2016 and 2017 in Birmingham, UK.

Participants 272 adults aged 18 years or more with a body mass index of 20 or more: 136 were randomised to a brief behavioural intervention and 136 to a leaflet on healthy living (comparator). Baseline assessments were conducted in November and December with follow-up assessments in January and February (4-8 weeks after baseline).

Interventions The intervention aimed to increase restraint of eating and drinking through regular self weighing and recording of weight and reflection on weight trajectory; providing information on good weight management strategies over the Christmas period; and pictorial information on the physical activity calorie equivalent (PACE) of regularly consumed festive foods and drinks. The goal was to gain no more than 0.5 kg of baseline weight. The comparator group received a leaflet on healthy living.

Main outcome measures The primary outcome was weight at follow-up. The primary analysis compared weight at follow-up between the intervention and comparator arms, adjusting for baseline weight and the stratification variable of attendance at a commercial weight loss programme. Secondary outcomes (recorded at follow-up) were: weight gain of 0.5 kg or less, self reported frequency of self weighing (at least twice weekly versus less than twice weekly), percentage body fat, and cognitive restraint of eating, emotional eating, and uncontrolled eating.

Results Mean weight change was −0.13 kg (95% confidence interval −0.4 to 0.15) in the intervention group and 0.37 kg (0.12 to 0.62) in the comparator group. The adjusted mean difference in weight (intervention−comparator) was −0.49 kg (95% confidence interval −0.85 to −0.13, P=0.008). The odds ratio for gaining no more than 0.5 kg was non-significant (1.22, 95% confidence interval 0.74 to 2.00, P=0.44).

Conclusion A brief behavioural intervention involving regular self weighing, weight management advice, and information about the amount of physical activity required to expend the calories in festive foods and drinks prevented weight gain over the Christmas holiday period.


2. The Christmas holidays are immediately followed by a period of hypercholesterolemia

Celebrating Christmas is associated with higher levels of total and LDL cholesterol.

Celebrating Christmas is associated with a higher risk of hypercholesterolemia.

A diagnosis of hypercholesterolemia should not be made around Christmas.


Background and aims

We aimed to test the hypothesis that levels of total and low-density lipoprotein cholesterol are increased after Christmas and that the risk of hypercholesterolemia is increased after the Christmas holidays.


We conducted an observational study of 25,764 individuals from the Copenhagen General Population Study, Denmark, aged 20–100 years. Main outcome measures were mean total and LDL cholesterol levels. Hypercholesterolemia was defined as total cholesterol >5 mmol/L (>193 mg/dL) or LDL-cholesterol >3 mmol/L (>116 mg/dL).


Mean levels of total and LDL cholesterol increased in individuals examined in summer through December and January. Compared with individuals examined in May–June, those examined in December–January had 15% higher total cholesterol levels (p < 0.001). The corresponding value for LDL cholesterol was 20% (p < 0.001). Of the individuals attending the study during the first week of January, immediately after the Christmas holidays, 77% had LDL cholesterol above 3 mmol/L (116 mg/dL) and 89% had total cholesterol above 5 mmol/L (193 mg/dL). In individuals attending the Copenhagen General Population Study in the first week of January, the multivariable adjusted odds ratio of hypercholesterolemia was 6.0 (95% confidence interval 4.2–8.5) compared with individuals attending the study during the rest of the year.


Celebrating Christmas is associated with higher levels of total and LDL cholesterol and a higher risk of hypercholesterolemia in individuals in the general population. Thus, a diagnosis of hypercholesterolemia should not be made around Christmas, and our results stress the need for re-testing such patients later and certainly prior to initiation of cholesterol-lowering treatment.

3. How COVID-safe Santa can save Christmas

(…) Visiting every house on earth, including regions where COVID-19 is eliminated and others where it’s out of control, presents a significant infectioncontrol challenge. Applying our traffic light system4 Santa would be coming from a low-risk ‘green’ jurisdiction given Santa Clause Village closed its borders more than 1,000 years ago and has had no reported cases of COVID-19.

Therefore, as the likelihood of Santa being infected with coronavirus before setting out on Christmas Eve is extremely low, he will not be asked
to quarantine on arrival in each jurisdiction. Nevertheless, given the high-risk nature of his job, he will require a negative test before flying. Additional precautions to adopt include making Santa’s sleigh covid-safe with fibreglass screens, and installation of a handsanitiser dispenser. And, along with Santa, the reindeer will be masked this year. We acknowledge that outdoor masks on reindeer might seem excessive and not evidencebased, but we feel this is a unique situation where being extra cautious makes sense.
Families can play their role in protecting this important frontline worker by staying at home – in bed. Santa assures us he only enters houses where children are sleeping so person-to-person contact should not be a problem. We can also help to keep him safe by making sure that if we leave him milk/brandy and cookies – which perhaps we should not given his aforementioned weight issue – we should use disposable cups and plates and have hand sanitiser on the table.
In the unlikely event that there are leftover brandy or biscuits, Mum and Dad should resist the temptation to finish them off and instead safely dispose of them. (…)

4. Too cold for warm glow? Christmas-season effects in charitable giving

This paper analyzes seasonal effects and their potential drivers in charitable giving. We conduct two studies to analyze whether donations to the German Red Cross differ between the Christmas season and summer. In study 1 we find that in the pre-Christmas shopping season prosocial subjects almost donate 50% less compared to prosocials in summer. In study 2 we replicate the low donations in the Christmas season. In an extensive questionnaire we control for several causes of this effect. The data suggest that the higher prosocials’ self-reported stress level, the lower the donations. The higher their relative savings, the lower the giving. Our questionnaire rules out that “donation fatigue” matters. That is, donations do not depend on the number of charitable campaigns subjects are confronted with and their engagement in these activities during Christmas season outside the lab.


6 Gedanken zu “Ein paar Weihnachtsstudien

  1. Schöne leichte Unterhaltung am Weihnachtsmorgen 🙂

    Ich finde es lustig, dass die Control Group, also die Gruppe mit der sie „nichts“ machen, einen bunten Zettel mit nützlichen Tipps bekommt. Es ist also wohlbekannt dass bunte Zettel nichts bringen, aber es ist genug damit die Leute nicht merken, dass sie in der Placebo-Gruppe sind 🙂

    • Kurios, Ich hab grad gestern erst einen alten Artikel auf slatestarcodex gelesen, eine Rezension von einem Buch, das Grenzen der Vernunft im Vergleich zur Tradition aufzeigt und da gibt es Maniok als Beispiel:

      And then there’s manioc. This is a tuber native to the Americas. It contains cyanide, and if you eat too much of it, you get cyanide poisoning. From Henrich:

      In the Americas, where manioc was first domesticated, societies who have relied on bitter varieties for thousands of years show no evidence of chronic cyanide poisoning. In the Colombian Amazon, for example, indigenous Tukanoans use a multistep, multiday processing technique that involves scraping, grating, and finally washing the roots in order to separate the fiber, starch, and liquid. Once separated, the liquid is boiled into a beverage, but the fiber and starch must then sit for two more days, when they can then be baked and eaten. Figure 7.1 shows the percentage of cyanogenic content in the liquid, fiber, and starch remaining through each major step in this processing.

      Such processing techniques are crucial for living in many parts of Amazonia, where other crops are difficult to cultivate and often unproductive. However, despite their utility, one person would have a difficult time figuring out the detoxification technique. Consider the situation from the point of view of the children and adolescents who are learning the techniques. They would have rarely, if ever, seen anyone get cyanide poisoning, because the techniques work. And even if the processing was ineffective, such that cases of goiter (swollen necks) or neurological problems were common, it would still be hard to recognize the link between these chronic health issues and eating manioc. Most people would have eaten manioc for years with no apparent effects. Low cyanogenic varieties are typically boiled, but boiling alone is insufficient to prevent the chronic conditions for bitter varieties. Boiling does, however, remove or reduce the bitter taste and prevent the acute symptoms (e.g., diarrhea, stomach troubles, and vomiting).

      So, if one did the common-sense thing and just boiled the high-cyanogenic manioc, everything would seem fine. Since the multistep task of processing manioc is long, arduous, and boring, sticking with it is certainly non-intuitive. Tukanoan women spend about a quarter of their day detoxifying manioc, so this is a costly technique in the short term. Now consider what might result if a self-reliant Tukanoan mother decided to drop any seemingly unnecessary steps from the processing of her bitter manioc. She might critically examine the procedure handed down to her from earlier generations and conclude that the goal of the procedure is to remove the bitter taste. She might then experiment with alternative procedures by dropping some of the more labor-intensive or time-consuming steps. She’d find that with a shorter and much less labor-intensive process, she could remove the bitter taste. Adopting this easier protocol, she would have more time for other activities, like caring for her children. Of course, years or decades later her family would begin to develop the symptoms of chronic cyanide poisoning.

      Thus, the unwillingness of this mother to take on faith the practices handed down to her from earlier generations would result in sickness and early death for members of her family. Individual learning does not pay here, and intuitions are misleading. The problem is that the steps in this procedure are causally opaque—an individual cannot readily infer their functions, interrelationships, or importance. The causal opacity of many cultural adaptations had a big impact on our psychology.

      Wait. Maybe I’m wrong about manioc processing. Perhaps it’s actually rather easy to individually figure out the detoxification steps for manioc? Fortunately, history has provided a test case. At the beginning of the seventeenth century, the Portuguese transported manioc from South America to West Africa for the first time. They did not, however, transport the age-old indigenous processing protocols or the underlying commitment to using those techniques. Because it is easy to plant and provides high yields in infertile or drought-prone areas, manioc spread rapidly across Africa and became a staple food for many populations. The processing techniques, however, were not readily or consistently regenerated. Even after hundreds of years, chronic cyanide poisoning remains a serious health problem in Africa. Detailed studies of local preparation techniques show that high levels of cyanide often remain and that many individuals carry low levels of cyanide in their blood or urine, which haven’t yet manifested in symptoms. In some places, there’s no processing at all, or sometimes the processing actually increases the cyanogenic content. On the positive side, some African groups have in fact culturally evolved effective processing techniques, but these techniques are spreading only slowly.

      Rationalists always wonder: how come people aren’t more rational? How come you can prove a thousand times, using Facts and Logic, that something is stupid, and yet people will still keep doing it?

      Henrich hints at an answer: for basically all of history, using reason would get you killed.

      A reasonable person would have figured out there was no way for oracle-bones to accurately predict the future. They would have abandoned divination, failed at hunting, and maybe died of starvation.

      A reasonable person would have asked why everyone was wasting so much time preparing manioc. When told “Because that’s how we’ve always done it”, they would have been unsatisfied with that answer. They would have done some experiments, and found that a simpler process of boiling it worked just as well. They would have saved lots of time, maybe converted all their friends to the new and easier method. Twenty years later, they would have gotten sick and died, in a way so causally distant from their decision to change manioc processing methods that nobody would ever have been able to link the two together.

      • @weißauchnicht:

        Sehr interessante Überlegungen!

        Ich würde ja sagen, wenn es dem Überleben dient, ist es vernünftig. „Vernünftig“ hier in der Allerweltsbedeutung, nicht unbedingt „streng auf Ratio und Logik basierend“, sondern eher so „es ist vernünftig bei Rot an der Ampel stehen zu bleiben“. Und hier ist es ja wirklich unmittelbar gut fürs Überleben.

        Die interessante Frage ist, was sagt es eigentlich über unseren akademisch-wissenschaftlichen Begriff der Vernunft aus, wenn es heißt „Rationalists always wonder: how come people aren’t more rational? How come you can prove a thousand times, using Facts and Logic, that something is stupid, and yet people will still keep doing it?. […] For basically all of history, using reason would get you killed“? Ist da nicht schon längst etwas gehörig schiefgelaufen?

        Was bedeutet es für die aktuelle Situation, wo man ja ganz ähnliche Dinge hört: „Es gibt aber keinen Beweis für… Das ist doch sinnlos… Das ist eine Überreaktion usw…“?

  2. Eiei, da wird wieder die Cholesterin-Sau durchs Dorf getrieben. Ich dachte so ganz langsam setzt sich die Erkenntnis durch das LDL nicht das eigentliche Problem ist und auch nur einen sehr schlechter Marker für die Gesundheit der Arterien und des Herz-Kreislaufproblems darstellt. Könnte natürlich damit zusammenhängen, das mit Statinen die eine oder andere Milliarde Gewinn gemacht wird … Aber was weiss ich Laie schon.

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