Have you made any New Year's resolutions for 2025? If you've decided to take care of your health, for example by eating better or taking up sports, you'll need motivation to make this new habit stick over time.
In a statement, Dr Ben Singh, a researcher at the University of South Australia, warns: " At the start of the year, many of us set goals and make plans for the months ahead – such as being more active, cutting down on sugar or making healthier food choices – but while conventional wisdom suggests that it only takes 21 days to adopt such habits, these claims are not based on evidence.", warns the researcher. This belief of the 21 days comes from the book " Psycho-Cybernetics » by American surgeon Maxwell Maltz.
With his team, Ben Singh scientifically evaluated the time needed for a healthy habit to become established over time. And the results indicate that the three-week time frame previously indicated is a huge underestimate. A new habit would actually take at least two months to establish itself.
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Behaviors that become automatic after more than 21 days
To obtain the values needed for their assessment, the researchers consulted six databases containing studies in which people assessed the time it took to achieve automaticity in health-related behaviors. A total of 20 studies comprising 2,601 participants with an average age between 22 and 74 years were ultimately selected. The healthy habits assessed varied widely. They included physical activity, a healthier diet, reducing sedentary behavior, but also more singular resolutions such as flossing.
Four of the studies examined focused specifically on the length of time it took to make the change. For example, the median time (the median divides two sets of statistics into two equal parts, one lower and one higher than the median) to maintain a healthier eating habit was 59 days, according to one study. Another suggested a time of 66 days, taking into account physical activity, better eating habits and water consumption.
Regarding the average time to adopt new eating habits and weigh oneself, participants in one study took 91 days to adopt this monitoring. Finally, a latest research has " reported that establishing the habit of daily stretching took an average of 106 days and 154 days for morning and evening stretching, respectively" . The researchers also note a " substantial individual variability (4 to 335 days) depending on different behaviors » studied.
While some people can quickly adopt a new habit, the vast majority do not do so in just three weeks. The authors of this study explain that, overall, their " Research indicates that habit formation typically takes 2 to 5 months for most health behaviors to become automatic.“.
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A few simple rules for adopting new habits over time
This study published in the journal Healthcare has many limitations (heterogeneous protocols, limited samples, etc.), and the data are not actually that easy to find. The researchers are well aware of this and emphasize that " This apparent paucity of studies directly measuring habit formation time highlights a significant gap between popular opinion and scientific evidence in this area.“.
Their results, however, remain important because determining an average duration for the formation of a new, healthier habit allows people to be given realistic expectations, the aim being to prevent them from losing their motivation after 21 days. The researchers also point out that certain rules generally help to encourage the adoption of a new habit: practicing it in the morning, choosing your own new habits, integrating them into a stable daily routine or having achievable goals.
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