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

Key messages

• Compared to no physical activity, any type of physical activity may help children with obesity to reduce their BMI slightly (the 'body mass index' is used to check if someone is a healthy weight) and may lead to considerably more minor unwanted events, but we are very uncertain about these results.

• We do not know if physical activity has any effect on the weight, body fat percentage, well-being, and blood sugar levels of children with obesity compared to no physical activity or another type or amount of physical activity. We also do not know if physical activity has any effect on the number of serious unwanted effects.

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

What is obesity?

Obesity is when a person has too much body fat. Worldwide, obesity amongst children (aged 0 to 9 years) has increased substantially since 1975. More than 300 million children and adolescents (aged 10 to 19 years) may be living with obesity by 2050.

Children with obesity are more likely to develop health problems such as heart disease, stroke, type 2 diabetes, some cancers, liver disease, asthma, joint and muscle problems, and infections later in life. Childhood obesity is also linked to higher rates of anxiety and depression.

Weight loss is the best way to reduce the health risks caused by obesity. In children, this is usually done through lifestyle changes such as doing more physical activity (e.g. running games or interactive video games that encourage movement (sometimes called 'exergaming')) and eating healthier foods.

What did we want to find out?

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

• reduce their BMI (the 'body mass index' indicates if someone is a healthy weight; their weight is divided by their height multiplied by itself, expressed as kg/m²) or BMI z-score (how someone's BMI compares to BMIs of others of the same age and sex);

• lose weight;

• improve their well-being;

• reduce body fat percentage or improve how body fat is distributed in the body; and

• lower their blood sugar levels.

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

What did we do?

We searched for studies that compared participating in physical activity to:

• no physical activity;

• another type or amount of physical activity.

The children 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 four studies including 517 children. The studies were small: the smallest included only 59 children and the largest, 222. Just under half of the children involved were girls (46%). Their average age was 9 years.

In three studies, the children did the physical activities for 12 or 13 weeks; the fourth study's physical activity programme lasted 32 weeks. The studies took place in three countries: one study each in Brazil and Iran, and two studies in the USA. In the American studies, 73% of the children were Black. The other studies did not describe the children's ethnicities.

• All four studies compared physical activity to no physical activity.

• One study also compared one type of physical activity (exergaming) to another type (swimming pool exercises).

• One study also compared doing 20 minutes versus 40 minutes of the same physical activities.

Main results

Physical activity versus no physical activity

Compared to no physical activity, children with obesity who participated in any physical activity programme may have:

• slightly reduced their BMI: the BMI of children in the active groups was on average 1.52 kg/m² lower (2 studies, 118 children);

• experienced more minor unwanted effects: children in the active groups may have been about 3.5 times more likely to experience minor unwanted effects (1 study, 222 children).

However, we are very uncertain about these results.

We do not know if physical activity makes any difference to children's:

• BMI z-score;

• weight;

• well-being;

• body fat percentage or how fat is distributed in the body;

• blood sugar levels;

• risk of experiencing serious unwanted events.

One type or amount of physical activity versus another type or amount

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

What are the limitations of the evidence?

We have limited confidence in the evidence because:

• there were few studies and they were small;

• the types of physical activities varied;

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

• three out of four studies did not report all their results.

How up to date is this evidence?

This evidence is current to December 2025.