A new study shows that overweight seven-year-olds have a higher risk of developing type 2 diabetes as adults, but only if they are still overweight by the time they hit puberty and beyond. It's well known that overweight in childhood leads to an increased risk of type 2 diabetes later in life.

Our research has previously shown that children who weigh just a couple of kilograms too much have a much higher chance of developing the disease and that this effect is more pronounced in girls than boys. The study was published in the New England Journal of Medicine.

But in this study, they did not have information from adults, for which we received some criticism, for exclusively studying child and not adult body mass indices (BMIs).  This meant that they could not judge whether weight loss before adulthood could help to reduce the risk of developing diabetes later in life.

Reduces the risk for type 2 diabetes

As reported in previous studies, they found an increased risk for type 2 diabetes in adulthood among boys who had overweight at age seven, thirteen, and older.

In our study, we showed that losing weight before reaching early adulthood subsequently reduced the risk of developing type 2 diabetes later on. Specifically, boys with overweight had the same risk of developing type 2 diabetes later in life as boys of normal weight, provided they reduced their BMI before puberty and maintained that weight loss until early adulthood. Boys were only more likely to develop type 2 diabetes as adults if the overweight remained by the time they reached puberty and beyond.

Even small changes in BMI count

Reducing BMI between the age of seven and eighteen was associated with a reduced risk of developing type 2 diabetes. Even boys with obesity could halve their risk by reducing their BMI from 'obesity' to 'overweight,' and they could remove the elevated risk entirely by bringing their BMI down to a normal level.

In contrast, every single increase in BMI was associated with an increased risk of type 2 diabetes. In general, there was an increased risk of type 2 diabetes among less educated eighteen-year-olds. But this could not explain the increased risk observed in men with overweight. And regardless of educational level, they could all reduce their risk of developing type 2 diabetes by losing weight before puberty.

We need to prioritize prevention of overweight in children

All in all, our results show that overweight around the age of puberty indicates a pattern of weight gain, which is particularly significant for the risk of developing type 2 diabetes. Today, as many as 20% of children are overweight. Our results suggest that preventing and treating overweight in prepubescent teenagers can help to reduce their risk of developing type 2 diabetes later on.

Research among girls is now needed

The next stage is to study whether women experience the same beneficial results by reducing their BMI before puberty and whether the benefits also apply to other weight-related conditions such as heart disease and stroke.

Other studies show that weight loss in adulthood delays the development of type 2 diabetes. Therefore, we expect that weight loss at any time from childhood to adulthood has the same beneficial effect.