Group health and wellness initiatives are more popular than ever. But just like freshmen level college courses, group size seems to be getting larger and larger. In a study recently published in the International Journal of Behavioral Nutrition and Physical Activity, researchers wanted to find out what group size was the most effective.



The researchers indicated that group-based weight-loss plans have been more effective than personal training in previous studies. They suggested that with more people comes more role-models, support, and competition.


Breaking Muscle Shop

However, much like how a larger class size in college can diminish your experience, the researchers suggested that health and fitness outcomes may benefit more from smaller group sizes. This was the first study of its kind to test how the size of a group affects individual results.


Study Design                     

66 overweight adults took part in this year-long study. They were divided into either a single large group of thirty participants, or three other small groups with twelve participants each. They were mostly women, although there were some men as well. While the average age was fifty years old, the only age requirement was that they were at or over 21. All the subjects belonged to an HMO, which is how they were recruited for the study, meaning that most of them were probably professionals as well.


For the first six months the participants met as a group roughly once per week to weigh in and learn about weight loss, discuss their progress, and practice skills needed to affect change. They performed something similar during the second half of the year to boost motivation, but only once per month.



The small groups won the day. After six months, the small-group members had doubled their results, with 14.3lb lost. The subjects in the large group had only lost seven pounds.


After a year, the results were even more divided. While the small group subjects had lost 15.4lb of bodyweight by then, which was not much more than their six-month measurement, the large-group subjects had gained some of the weight back, with a total of 3.7lb lost.


This means the small group size was more than four times as effective for weight loss over the course of a year. Not only did the small group participants achieve greater weight loss on average, but the they were also more likely to achieve a significant level of weight loss on their own.


Why Smaller Groups Were Better

One of the reasons for greater success was that the participants of the smaller group felt as though they were a part of something. They reported feeling more engaged. As noted by the researchers, this suggests that “smaller group settings provide more positive, cohesive, and collaborative atmospheres.”


The researchers said adherence made the biggest difference between success in the small group and lack of it in the large group. Specifically, the subjects had adherence to the behavioral modification strategies, like self-monitoring. The more intimate group dynamic in the smaller group resulted in better follow-through.


If you’re looking to lose weight, or achieve other health and fitness related goals, this study has your answer. Adding a social component reinforces your ability to stick to your plan, resulting in greater success.



1. Gareth Dutton, et. al., “A randomized trial comparing weight loss treatment delivered in large versus small groups,” International Journal of Behavioral Nutrition and Physical Activity 2014, 11:123


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