Systematic review finds health habits can form in as little as two months, but individual variability ranges from 4 to 335 days. Morning routines and self-selected habits show the strongest results.

Study: Time to Form a Habit: A Systematic Review and Meta-Analysis of Health Behaviour Habit Formation and Its Determinants. Image Credit: Josep Suria/Shutterstock.com

 

In a recent systematic review in Healthcare, researchers summarized existing research on the time it takes to form health-related habits and identified factors influencing their formation.

Their findings indicate that there is significant variability across individuals in terms of how long it takes to form health-related habits.

Still, interventions can significantly improve the strength of habit formation. They also suggest that enjoyment is a critical component of maintaining healthy behaviors.

Background

Developing and maintaining health-related habits is essential for promoting healthy behaviors and preventing chronic diseases. Habit formation involves repeatedly performing a behavior in a stable context until it becomes automatic—requiring minimal thought or effort.

This process is critical for long-term behavior change and is influenced by factors like dopamine (which links actions to rewards) and “friction” (the ease or difficulty of performing a behavior).

A popular claim suggests habits can form in 21 days, but research shows this timeline varies widely depending on the behavior, individual, and context.

Practical strategies for building habits include linking new habits to existing routines, starting with small, achievable goals, and practicing consistently. Repetition in a stable context accelerates habit formation.

Previous studies, focused primarily on physical activity, have found that habit strength moderates the relationship between intentions and behaviors and predicts long-term adherence. However, less is known about how long it takes to form habits across a broader range of health behaviors.

About the study

The systematic review addresses an existing research gap, aiming to provide a deeper understanding of the time and effort required to form sustainable health-related behaviors and expand the evidence base beyond physical activity interventions.

Researchers identified relevant experimental studies through comprehensive searches across six databases, focusing on research that targeted adults, included habit-focused outcomes, and examined health-related behaviors such as exercise and diet.

Out of 3,448 identified records, 20 studies were included in the final analysis after a rigorous screening process.

These studies, involving 2,601 participants aged between 21.5 and 73.5 years, examined various health-related habits, such as healthy eating, physical activity, dental flossing, and water consumption.

Participants were recruited from diverse settings, including universities, the general public, hospitals, and specific populations like older adults or those with obesity. Studies employed different delivery methods, including mobile apps, text/email messaging, workshops, and informational leaflets.

Findings

Four studies investigated the time needed for habits to develop. Healthy eating habits required a median of between 59 and 66 days to form, although not all participants reached the level of automaticity.

For self-reported habits, such as healthy eating and stretching, the time to habit formation varied from 91 to 154 days, depending on the specific behavior and the context within which it was practiced.

A meta-analysis of 12 studies revealed significant improvements in habit strength across various interventions, with a moderate-to-large overall effect size. However, the effect sizes varied by behavior.

Flossing demonstrated the largest effect, followed by diet and physical activity, both of which showed moderate effects. In contrast, no significant effects were observed for sedentary behavior.

Several factors were identified as critical to habit formation. The initial stage of habit development is influenced by self-chosen habits and specific implementation plans, which improve initial habit strength.

Repetition and context stability further contribute to habit formation, with consistent practice and strategic timing, such as morning habits, shown to strengthen behaviors. Early repetitions yield significant automaticity gains, although these gains eventually plateau over time.

The development of automaticity is also shaped by factors such as enjoyment of the activity, detailed planning, and preparatory routines, such as setting out exercise clothes to encourage regular physical activity.

Conclusions

This meta-analysis revealed significant improvements in habit scores across behaviors, with the largest effects on physical activity, diet, and flossing.

Notably, morning practices and simple, repetitive behaviors such as flossing were easier to automate, while complex habits, notably healthy eating, took longer to form.

Interventions lasting between two and five months were more effective than short-term approaches. The review highlighted gaps in research, emphasizing the need for long-term studies using objective measures.

These findings emphasize the importance of consistent practice in stable contexts and suggest that tailored interventions can support habit formation.

Although the time required to achieve automaticity varies across behaviors, interventions that promote sustained repetition, enjoyment, and strategic planning can enhance the development and maintenance of habits.

Findings suggest individuals and health practitioners should focus on sustained efforts, realistic timelines, and supportive strategies for long-term habit formation.