Resolution solution: Does it really take 21 days to adopt a new habit?

On average, it takes between two and eight months to change your habits. On average, it takes between two and eight months to change your habits. Image: Shutterstock

A new year brings new resolutions, whether it's getting back into exercise, eating a healthier diet or cutting screen time. And, according to a theory that has been around for decades, it supposedly takes 21 days for these new behaviors to become routine and take root in our daily lives. But is this really the case?

The origin of this theory dates back to the 1960s, when the American plastic surgeon Maxwell Maltz hypothesized that his patients needed at least 21 days to get used to their new appearance and form a different "mental image" of themselves. This observation features in his famous book "Psycho-Cybernetics," which has become a bestseller and a reference in the world of wellness.

Sixty years on, experts are calling this 21-day theory into question. A study conducted by researcher Phillippa Lally of University College London in 2009 reports that a new habit takes an average of 66 days to become automatic. This time-frame can vary considerably depending on the person or circumstances, ranging from 18 to 254 days. According to the researcher, it's difficult to predict the variation in these timescales, but she suggests that it's probably easier to consider a habit as having become automatic when it's simple. Drinking a glass of water in the morning requires less effort than getting into the habit of exercising regularly, for example, which may give the impression that the first habit is assimilated more quickly than the second.

This idea is supported by a separate study, published in January 2023 in the journal PNAS. "Contrary to the popular belief in a 'magic number' of days to develop a habit, we find that it typically takes months to form the habit of going to the gym but weeks to develop the habit of handwashing in the hospital," write the researchers. Their study was based on data from 30,000 exercisers and 3,000 hospital employees. After examining 12 million exercise sessions and over 40 million hand-washings, the scientists determined that it took an average of six months to get into the habit of exercising, whereas getting into the habit of handwashing was more likely to take a week.

Thomas Boraud, research director in neuroscience at France's CNRS National Center for Scientific Research and head of the Neurodegenerative Diseases Institute (IMN) in Bordeaux, reiterates this notion by shedding light on the factors at play in the formation of habits. "The longer a habit lasts, the harder it is to stop. And the older you are, the more complicated it is to get rid of certain behaviors. The individual's personality also plays a role. Some people are more sensitive to change than others," he told Ouest France. For him, establishing an average time-frame for successfully adopting a new behavior, or quitting an old habit, would be "wishful thinking."

So, in this New Year, as we strive to let go of our bad habits, it's important to bear in mind that the road to change can take longer than the famous 21 days, and that it depends on a variety of individual factors. But don't worry, there are ways of sticking to these goals in the long term. To increase your chances of success, researcher Phillippa Lally advises considering only adopting those habits that you really want to integrate into your life.