At 44, I’m old enough to remember a time when numbers were everywhere. I remember when no one knew how many calories were in anything they ate, or what their resting heart rate was, or how many steps they walked today, or how long they spent on it. REM sleep last night. Daily human activity – eating, walking, to sleeppurchase – remain, but they are arranged with an arithmetic layer. It happened gradually, this introduction of numbers into our lives to live by: kilocalories, grams of macros, heart rate zones, heart rate variability, steps, elevation gain, liters, hours of direct sunlight…
Progressive digital infiltration took two forms: normalizing tracking and supplementing tracking with targets and limits. Not long ago, basic health advice consisted of innocuous words like “don’t eat too much”, “get fresh air”, “be active”. Now what is considered enough or too much has become numbers: 10,000 steps a day, 150 minutes of moderate exercise a week, 5 servings of fruits and vegetables a day, 2 liters of water a day…
I remember when getting a glass of water was something you did when you had a meal or were very thirsty; Now it’s not uncommon to aim for a certain number of water bottle fills per day and treat detectable thirst as a signal that only appears when things have gone horribly wrong. This is what happened screen timesun exposure, protein intake, BMI, sleep score: In all these cases, numerical criteria are now available and they have a complex downstream effect.
If one is so inclined, numerical norms can be transformed into personal ones goals. In this way, numbers create behavioral expectations: If you haven’t “put in your steps” or taken your quota of moving minutes today, and it’s 10 p.m., you might conclude that you should go for a walk. Thus, changes in what tasks continue to be a major driver of human behavior: from experiences (do I feel hungry, thirsty, tired, restless?) to digital health tips and performance indicators.
And it can be argued that this is a good and necessary thing: this evidence shows that certain habits and norms are important for health, and so are the technologies and public health campaigns designed to encourage them. But when we dig into the details of how the numbers came about, things start to look a little more murky than we might expect.
Here are some examples of how much skepticism there is often in the exact range of health numbers:
- For 10 thousand steps per daynon-commercial selection (by a Japanese pedometer manufacturer; see This is a Harvard health report history) led to behavioral change, which in turn led to research that revealed benefits. Further research (and common sense!) has suggested that there is nothing magical about 10k, and that diminishing returns or even negative effects can occur at much lower levels. (see Ding et al. 2025 for regular review and meta-analysis.)
- Body mass index began as a descriptive tool for generating statistics on the bodies of white European males as part of the research of the Belgian polymath Adolphe Quetelet. average personaverage person He believed that “the mean value of a distribution should be of primary importance in the study of human characteristics” (Tafreshi, 2022) and his ideas had an important influence on the development of eugenics by Francis Galton (Strawberry, 2015). Only later did BMI gain direct normative power as a spectrum with cutoffs that transform continuous distributions into normal categories for optimizing human health. It does not live up to its popular modern roles as an indicator of obesity and as an indicator of health or predictor of mortality risk. (Nuttall, 2015).
- Water consumption guidelines for the first time in the context of public health in the US food and Food The Council Recommendation of 1945, which states that total water intake is mainly derived from food (for an overview see Stuckey and Kavouras, 2020). For years, the daily number of 2 liter / 8 x 8 oz glasses was held up and misinterpreted as the amount to be ingested in the form of plain water. First author of the article (Yamada et al., 2022) on global changes in water consumption said: “The current recommendation is not scientifically supported at all. Most scientists are not sure where this recommendation came from.” The actual need for fluid intake is very variable (especially depending on the level of physical activity) and thirst is well indicated, but nevertheless, the number of 2 liters seems to have succeeded in a certain western type to drink more water than ever, and many others to believe that they should drink water.
- Aim to consume 2000 calories per day of self-reported daily intake values collected by the US Department of Agriculture were not only significantly underreported, but also aggregated to encourage people to eat less (see history overview Here). The instructions are now everywhere in the nutritional information on the packaging, which informs us not only what proportion of our supposedly ideal daily energy intake this piece of food represents, but also about its macro and micronutrients with dubious scientific evidence (Heath et al., 2010). As with every other metric I’ve mentioned, the individual variation in what is considered optimal is huge and is ignored by the monolithic 2k.
This obscure history does not mean that any health/lifestyle guidelines do not have a solid scientific basis.
Epidemiological findings, for example, show that greater physical activity (PFE) is associated with lower risk of cardiovascular disease (CVD) and all-cause mortality (Kraus et al., 2020), including prospective studies that do not allow us to definitively draw conclusions about causality but at least to observe that the relevant factor has temporarily overtaken the result. But here too, numbers are the most important part of the picture. As Kraus and colleagues summarize it: “PA associations with beneficial health outcomes begin at very modest amounts (one-third of guidelines); any MVPA is better than none; adherence to the 2008 PA guidelines reduces mortality and CVD risk by about 75 percent of the benefits of physical activity; guideline-recommended amounts reduce risk even further, but more PA is needed to achieve health benefits.”
So, crystallizing the powerful form of powerful reason into specific numbers, such as 150 minutes of moderate exercise per week, involves oversimplification. The characteristics of how the movement is distributed during the day and week, what type of activity and how the duration and intensity are affected, how these variables are affected by personal and contextual factors – all this is ignored in the number of widespread broadcasts and how it affects the settings of the fitness device, such as “minutes of intensity” and “heart points”.
Thus, the amount of confirmatory evidence and interpretive validity vary greatly at the population and individual level. The challenge of what each of us needs to be healthy (whatever that means to us personally) is now subsumed into an oversimplified singular metric. They often reflect reality poorly and try to shape it as sensitively as a hammer.
How can figures with such a shadowy history have such a psychological and behavioral resemblance to us? This is the turn..
