Body size during childhood — a marker of overweight and obesity — is linked to the risk for developing type 1 diabetes throughout life, according to a new analysis published in the journal Nature Communications.
As the study authors write, the incidence of type 1 diabetes — the proportion of people who develop the condition in a given year — has doubled over the last 20 years. Type 1 diabetes develops when the body’s immune system attacks the insulin-producing cells of the pancreas — first reducing, then eventually eliminating (or nearly eliminating), the organ’s ability to produce insulin. Since insulin is necessary to store and use glucose — the body’s preferred energy source — people with type 1 diabetes depend on outside insulin to survive.
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There are several hypotheses that researchers have proposed to explain why type 1 diabetes has been on the rise. One potential explanation is that the makeup of people’s gut bacteria has changed over time due to dietary and hygiene factors, with the immune system responding differently to this bacterial environment in the body. Other potential explanations include increasing rates of viral infections that activate the immune system in people who develop type 1, and decreasing levels of vitamin D due mostly to less sun exposure — with vitamin D playing a role in regulating the immune system.
Another hypothesis, though, is that rising levels of childhood obesity could be contributing to the “fragility” of insulin-producing pancreatic beta cells early in life, making them more susceptible to an attack by the immune system. Under this potential explanation, one effect of an unhealthy diet in childhood — containing highly processed carbohydrates that stimulate insulin production — could be to “wear out” pancreatic beta cells in a way that damages them, possibly making them look more to the immune system like an outside “intruder” that needs to be attacked or damaging these cells’ defenses against such an attack.
For the latest analysis, researchers at the University of Bristol in England were interested in exploring whether data supports the idea that childhood obesity could be behind the observed increase in type 1 diabetes. To do this, they used data from multiple studies — known as a meta-analysis — with a combined total of 15,573 participants with type 1 diabetes, and 158,408 participants without diabetes. The researchers aimed to find out whether a larger body size during childhood increases the risk for type 1 diabetes throughout life by applying a technique called Mendelian randomization. This technique involves looking at the effect not of childhood body size directly — but instead of genes that are linked to childhood body size — on the risk of developing type 1 diabetes. Since people can’t choose the genetic traits they inherit, this technique is a way to focus directly on how a trait (childhood body size) is linked to an outcome (developing type 1 diabetes) without having to account for how other factors might affect the outcome — factors like nutrition, social and economic status, or other health conditions.
Larger childhood body size linked to increased risk of type 1 diabetes
The researchers found that for every difference between a smaller and larger body size category, participants were 2.05 times as likely to develop type 1 diabetes throughout life. When the researchers adjusted for participants’ body size at birth and during adulthood, the link between childhood body size and diabetes risk got even stronger — with every difference between a smaller and larger body category linked to 2.32 times the risk of developing type 1 diabetes. Type 1 diabetes wasn’t the only health condition that the researchers found was linked in this way to childhood body size — they also found similar links to asthma, eczema, and hypothyroidism. But the researchers found that unlike in the case of type 1 diabetes, adjusting for body size later in life resulted in a weaker link between childhood body size and these other health conditions.
“Our findings support a causal role for higher childhood body size on risk of being diagnosed with [type 1 diabetes],” the researchers concluded, while noting that the link between childhood body size and “other immune-associated diseases is likely explained by a long-term effect of remaining overweight for many years” over the course of life. In other words, maintaining a healthy body weight during childhood is critical when it comes to reducing a person’s lifetime risk for type 1 diabetes — since body size at this phase of life is linked to a person’s lifetime risk for type 1 regardless of whether they remain overweight or obese following childhood.
Want to learn more about raising a child with type 1 diabetes? Read “The Type 1 Diabetes Diagnosis” and “Type 1 Diabetes at School: What Personnel Need to Know.”
