Positive Health Behaviours and How to Make Them Last

25 min

Sixty-six days, not twenty-one

You may have heard that it takes 21 days to form a habit. In a study published in 2010, Phillippa Lally and colleagues at University College London tested the idea. Volunteers each chose one healthy behaviour to do every day in the same situation, such as “after breakfast, drink a glass of water” or “before dinner, go for a 15-minute run”, and each day they rated how automatic it felt.

Automaticity rose quickly at first and then levelled off. On average, it took 66 days to get close to the maximum, but the range was huge, from 18 to 254 days, and exercise habits took longer than drinking water. Missing a single day did not ruin progress. Healthy behaviours, the study suggests, are less about willpower on one heroic day than about repeating a simple action in the same situation until it runs by itself.

Definition

Positive health behaviour: an action that protects or improves health, such as exercising, sleeping enough, eating well or washing hands with soap.

Habit: a behaviour triggered automatically by a familiar situation, because it has been repeated in that situation many times.

Intention–behaviour gap: the gap between what people intend to do and what they actually do.

Implementation intention: an “if–then” plan that links a specific situation to a specific action: “If it is 5 p.m., then I will walk for 20 minutes.”

1. Key positive health behaviours

Behaviour	Guidance	Source
Physical activity (ages 5 to 17)	An average of at least 60 minutes a day of moderate-to-vigorous activity, with vigorous and muscle- and bone-strengthening activity on at least 3 days a week; limit time sitting and on screens	WHO, 2020
Physical activity (adults)	150 to 300 minutes a week of moderate activity, or 75 to 150 minutes of vigorous activity	WHO, 2020
Sleep (ages 13 to 18)	8 to 10 hours in every 24 hours	American Academy of Sleep Medicine, 2016
Diet	At least 400 g (five portions) of fruit and vegetables a day; free sugars below 10% of energy; less than 5 g of salt a day	WHO healthy diet fact sheet
Hygiene	Washing hands with soap, especially after the toilet and before eating; a review of studies found it reduced the risk of diarrhoea by around 40%	Curtis and Cairncross, 2003
Safety	Helmets on motorcycles and bicycles, seatbelts, no phone use while crossing roads	Road safety guidance
Preventive care	Vaccinations, sleeping under mosquito nets, dental care, health checks and screening	Ministry of Health, RBC
Sexual health	Choosing to delay sex, using condoms, testing and treatment	RBC
Mental well-being	Time with friends and family, talking about problems, time outdoors, avoiding alcohol and drugs as a way of coping	WHO

Cyclists ride along a tree-lined Kigali road during a Car Free Day, when the City of Kigali closes roads to cars on some Sunday mornings so that people can cycle, walk, run and exercise together. Photo: Fabos ishimwe, CC BY-SA 4.0, via Wikimedia Commons.

2. From intention to habit

Most people already intend to be healthy. Reviews by Paschal Sheeran found that intentions explain less than a third of the differences in what people actually do. Several techniques help close the gap:

Implementation intentions. A review of 94 studies by Peter Gollwitzer and Paschal Sheeran (2006) found that “if–then” plans had a medium-to-large effect on reaching goals, from exercising to attending screening.
Repeat in the same situation, so that the situation becomes the trigger (Figure 1).
Change the environment: keep a water bottle on your desk, fruit where you can see it, your phone outside the bedroom at night. In schools, handwashing points placed between toilets and classrooms make washing easy.
Self-monitoring: record what you do, such as minutes of activity or hours of sleep.
Social support: exercise with a friend; mass events such as Kigali’s Car Free Day turn exercise into a shared activity.

Figure 1. How automaticity grows with repetition (schematic, based on Lally and colleagues, 2010).

City of Kigali: “Video highlights: Kigali #CarFreeDay”. Watch for the different activities people take part in, and consider which techniques from this lesson the event uses to make exercise easier.

Important

Evaluate the evidence. Lally’s study is valuable because it followed real behaviours day by day, but it was small (fewer than a hundred volunteers), the participants were mostly university students, and automaticity was self-rated. The 66-day figure is a median, not a rule. Implementation-intention research is extensive, but effects in the laboratory are often larger than in long-term real-life behaviour change. Guidelines such as WHO’s are based on large bodies of evidence, but meeting them depends on opportunities: safe places to exercise, affordable fruit and vegetables, and time.

Warning

Common mistake: treating a missed day as failure. Lally found that missing a single day did not undo progress; giving up after a slip is what stops habits forming.

Tip

Memory hook: to build a habit, make it small, same place, same time, and easy to start.

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Practice

Define a habit and an implementation intention.
What did Lally and colleagues find about how long habits take to form?
State the WHO guidance on physical activity for 15-year-olds.
Write two implementation intentions for an S6 student who wants to sleep 8 hours a night and drink more water.
Explain how a school could use the environment to increase handwashing.
Explain the intention–behaviour gap and suggest two ways to close it.
Evaluate Kigali’s Car Free Day as a way of promoting physical activity, using concepts from this lesson.

Show answersHide answers

Habit: a behaviour automatically triggered by a familiar situation after much repetition. Implementation intention: an “if–then” plan linking a situation to an action.
Automaticity rose quickly then levelled off; the median time to approach the maximum was 66 days, with a range of 18 to 254 days; missing one day did not ruin progress; exercise took longer than simpler habits.
At least 60 minutes a day on average of moderate-to-vigorous activity, with vigorous and muscle- and bone-strengthening activity at least 3 days a week, and limited sitting and screen time.
For example: “If it is 9.30 p.m., then I will put my phone outside my room and go to bed.” “If I sit down for evening study, then I will fill my water bottle first.”
Place handwashing points with soap between toilets and classrooms, keep them filled, add reminders or pictures near them, and build handwashing into routines such as before lunch.
The gap between what people intend and what they do. Ways to close it: implementation intentions, repeating the behaviour in the same situation, changing the environment, self-monitoring, social support.
Strengths: social support and enjoyment, a regular time and place (a cue), safe car-free roads (environmental change), sometimes free health checks. Limits: it happens only on some days, so it may not build daily habits on its own; people far from the routes may not benefit; its effects on population activity levels would need evaluation.

Sources and credits

Photos: “Cityofkigali 128”, Fabos ishimwe, via Wikimedia Commons, CC BY-SA 4.0; “Kirwa Primary School Handwashing Facility”, E. Dusingizumuremyi, SuSanA Secretariat, via Wikimedia Commons, CC BY 2.0.
Works described: Lally, P. and others (2010), “How are habits formed: modelling habit formation in the real world”, European Journal of Social Psychology 40; World Health Organization (2020), Guidelines on Physical Activity and Sedentary Behaviour; Paruthi, S. and others (2016), “Recommended amount of sleep for pediatric populations”, Journal of Clinical Sleep Medicine 12; World Health Organization, Healthy diet fact sheet; Curtis, V. and Cairncross, S. (2003), “Effect of washing hands with soap on diarrhoea risk in the community”, The Lancet Infectious Diseases 3; Sheeran, P. (2002), “Intention–behavior relations”, European Review of Social Psychology 12; Gollwitzer, P. M. and Sheeran, P. (2006), “Implementation intentions and goal achievement”, Advances in Experimental Social Psychology 38.
Video: “Video highlights: Kigali #CarFreeDay”, City of Kigali, embedded from YouTube.

Written by Ganzaa: the text, the table, Figure 1 and the exercises. The photos are used unchanged. This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.

1Sixty-six days, not twenty-one

21. Key positive health behaviours

32. From intention to habit

Sixty-six days, not twenty-one

1. Key positive health behaviours

2. From intention to habit