Childhood obesity is linked to an increased risk of chronic health conditions and premature death. A recent study that quantified the impact found that severe obesity in early years could cut life expectancy by half.

This means that a child with severe obesity at age 4 has only a life expectancy of 39 if the individual does not lose weight. However, losing weight could add decades back to their lives.

"While it's widely accepted that childhood obesity increases the risk of cardiovascular disease and related conditions such as type 2 diabetes (T2D) and that it can reduce life expectancy, evidence on the size of the impact is patchy. A better understanding of the precise magnitude of the long-term consequences and the factors that drive them could help inform prevention policies and approaches to treatment, as well as improve health and lengthen life," said Dr. Urs Wiedemann who presented the study at the European Congress on Obesity (ECO) in Venice, Italy.

To estimate the effect of childhood obesity on cardiovascular disease, type 2 diabetes, and life expectancy, researchers created an early-onset obesity model. The data from 50 existing studies with more than 10 million participants from countries around the world were used for the model.

The studies took into account factors such as the age of obesity onset, obesity duration, irreversible risk accumulation, and severity of obesity. The severity of obesity was calculated based on BMI Z-scores, which define how strongly an individual's BMI deviates from the normal for their age and sex.

"The model shows that earlier onset and more severe obesity increase the likelihood of developing related comorbidities. The early onset obesity model also shows that a higher BMI Z-score at an early age leads to a lower life expectancy," the news release stated.

The model also estimated the effect of weight loss on life expectancy and long-term health. Researchers noted that earlier weight loss returns more years of life than later weight loss.

"The early onset obesity model shows that weight reduction has a striking effect on life expectancy and comorbidity risk, especially when weight is lost early in life," Dr. Wiedemann said.

"The impact of childhood obesity on life expectancy is profound. It is clear that childhood obesity should be considered a life-threatening disease. It is vital that treatment isn't put off until the development of type 2 diabetes, high blood pressure or other 'warning signs' but starts early. Early diagnosis should and can improve quality and length of life," Dr. Wiedemann added.