What are the effects of physical activity for adolescents with obesity?

Key messages

• Any type of physical activity may slightly reduce body weight, waist size, and body fat percentage in adolescents with obesity, compared to no physical activity.

• We do not know if physical activity has an effect on other measures of weight, body size, or health problems due to obesity, compared to no physical activity.

• We need larger, longer-lasting, and better-quality studies to be more certain about the effects of physical activity on adolescents with obesity.

What is obesity?

Obesity is when a person has too much body fat, which can harm their health. Worldwide, obesity amongst adolescents (aged 10 to 19 years) has tripled since 1990, and more than 300 million children and adolescents may be living with obesity by 2050.

Obesity during childhood and adolescence can negatively affect physical and mental health, and may increase the risk of having cancer, liver disease, or kidney disease in adulthood.

Weight loss is the best way to reduce the health risks caused by obesity. This is usually done through lifestyle changes such as doing more physical activity (e.g. swimming, running, weight-lifting) and eating healthier foods, or with surgery or medication.

What did we want to find out?

We wanted to find out if, compared to no physical activity, physical activity helps adolescents with obesity:

• lose weight and reduce their BMI (the 'body mass index' is used to check if someone is a healthy weight; their weight is divided by their height multiplied by itself), BMI z-score (how someone's BMI compares to BMIs of others of the same age and sex), waist size, and body fat percentage;

• lower their blood sugar levels and insulin resistance (insulin is a hormone that helps to control blood sugar levels).

We also wanted to find out if one type of physical activity was better than another type at producing these effects, and if the physical activity programmes led to any unwanted, harmful events.

What did we do?

We searched for studies that compared participating in physical activity (such as doing aerobic exercise, weight-lifting, or playing football) to:

• no physical activity;

• another type of physical activity (for example, high-intensity exercise compared to moderate-intensity exercise).

The adolescents needed to do the physical activities for at least 12 weeks. We compared and summarised the results of the studies and rated our confidence in the evidence, based on factors such as study methods and number of participants.

What did we find?

We found 30 studies including 1508 adolescents. The studies were small: the smallest included only 21 adolescents and the largest, 106. Just under half of the adolescents involved were female (46%). Their average age ranged from 10 years to nearly 17 years. The studies took place in 15 countries: 5 in Tunisia; 4 each in China and Iran; 3 in Brazil; 2 each in Canada, Spain, and the USA; and 1 each in Australia, Estonia, India, Mexico, South Korea, Sweden, Taiwan, and Thailand.

Most studies lasted 12 or 13 weeks; the longest study lasted 32 weeks.

We organised the studies' results into two broad comparisons:

• any type of physical activity (e.g. aerobic exercise, active video-gaming) compared to no physical activity (22 studies);

• one type of physical activity compared to another type (17 studies).

Main results

Physical activity versus no physical activity

Compared to no physical activity, any type of physical activity may slightly reduce:

• body weight: adolescents in the active groups weighed on average 1.88 kg less (17 studies, 749 adolescents);

• waist size: in the active groups, adolescents' average waist size was 2.88 cm smaller (10 studies, 476 adolescents);

• body fat percentage: in the active groups, adolescents' average body fat percentage was 2.96% lower (9 studies, 313 adolescents).

We are very uncertain about the effect of any type of physical activity on:

• BMI;

• BMI z-score;

• blood sugar levels;

• insulin resistance;

• unwanted, harmful events.

One type of physical activity versus another type

We are very uncertain about the effect of one type of physical activity compared with another on any of the points we were interested in.

What are the limitations of the evidence?

We have limited confidence in the evidence because:

• the studies were small;

• the types of physical activities varied;

• the studies' reporting of their methods and findings was poor;

• some studies did not report all their results;

• no studies reported on unwanted, harmful events.

The studies comparing two different types of physical activity were quite varied, which meant we were mostly unable to combine their results to produce strong evidence. Therefore, we do not know whether one type of physical activity is better than another.

How up to date is this evidence?

This evidence is current to December 2025.