NEW ORLEANS – Obesity in adolescence is linked to an increased risk for type 1 diabetes onset in adulthood, new research suggests.
These new data, from Israeli military recruits followed for over a decade, suggest that obesity may be playing a causal role in type 1 as well as type 2 diabetes.
The incidence of type 1 diabetes has been increasing by about 2%-3% annually over recent decades, but the reasons aren’t clear. The study is the first to examine the role of obesity in adolescence and type 1 diabetes in young adulthood, and also the first to examine the question of using antibody status as part of the criteria for a type 1 diagnosis.
The findings were reported at the annual scientific sessions of the American Diabetes Association by Gilad Twig, MD, PhD, professor of medicine at Sheba Medical Center, Tel HaShomer, Israel. “For people who might have a high risk for developing type 1 diabetes, these results emphasize the importance of maintaining a normal weight,” he said in an interview. He noted that, although this recommendation applies to everyone, “here it’s becoming more precise for the population – more individualized in the sense that this might specifically help you.”
Naveed Sattar, PhD, professor and honorary consultant in cardiovascular and medical sciences at the University of Glasgow, said in an interview that carrying too much weight “will make the pancreas have to work harder to make insulin to keep the sugar normal. So, if you’re stressing the system and the pancreas is already likely to fail, it will fail faster.”
Dr. Naveed Sattar
Clinically, Dr. Sattar said, “Lifestyle does matter to the risk of developing type 1 diabetes. The weighting may be different [from type 2]. The major factor in type 1 is still the genetics, but if you have a family history of type 1 and your genetic potential is greater, you will minimize your risk by staying leaner.”
Study highlights that type 1 is not always ‘juvenile’
In addition to countering the long-held belief that type 1 diabetes is primarily a condition of thin individuals and unrelated to obesity, the data also reinforce the emerging recognition that type 1 diabetes isn’t always “juvenile” and in fact often arises in adulthood.
“About half of all cases of type 1 diabetes develop after age 18. By reputation, people think it’s a disease of children. But it’s begun to grow so that now 50% of cases occur after late adolescence,” noted Dr. Twig.
Dr. Sattar pointed to a UK Biobank study showing that nearly half of all cases of type 1 diabetes arise after age 30 years. “You absolutely can get type 1 in adulthood. It’s not rare.”
Direct correlation seen in otherwise healthy young people
The retrospective nationwide cohort study included 1,426,362 17-year-olds (834,050 male and 592,312 female) who underwent medical evaluation prior to military conscription starting in January 1996 and followed them through 2016. At baseline, none had a history of dysglycemia.
The data were linked with information about adult-onset type 1 diabetes in the Israeli National Diabetes Registry. In all, 777 incident type 1 diabetes cases were recorded over the study period, with a rate of 4.9 cases per 100,000 person-years.
Over a median follow-up of 11.2 years, there was a graded incidence of type 1 diabetes across BMI groups from underweight to obesity, from 3.6 to 8.4 cases per 100,000 person-years.
After adjustment for sex, birth year, age at study entry, education, and cognitive performance with BMI 5th-49th percentiles as the reference, the hazard ratios were 1.05 for the 50th-74th BMI percentiles, 1.41 for 75th-84th, 1.54 for those who were overweight, and 2.05 for those with obesity.
Every 5-unit increment in BMI corresponded to a 35% greater incidence of type 1 diabetes (adjusted hazard ratio 1.35) and every one increment was associated with a 35% greater risk (1.25), both values significant.
Sensitivity analyses resulted in similar findings for those with no other chronic health conditions at baseline. The results also didn’t change in a separate analysis of 574,720 subjects in whom autoantibody data were available to confirm the type 1 diabetes diagnosis.
Hypotheses for mechanisms
The mechanism for the association isn’t clear, but in a simultaneously published article in Diabetologia, Dr. Twig and colleagues outline several hypotheses. One relates to the growing evidence of a link between various autoimmune conditions, which point to the possibility of elevated adipokines and cytokines in obesity diminishing self-tolerance by promoting proinflammatory processes.
The authors cite data from the TrialNet Pathway to Prevention study of relatives of people with type 1 diabetes in which participants who were overweight and obese had an increased risk of islet autoantibody expression. However, not all data have supported this finding.
“Obesity is related to several other autoimmune conditions, so it’s not a complete surprise it might be related to another,” Dr. Twig noted.
Other possibilities include vitamin D deficiency, a high-fat diet, and alterations in gut microbiota.
And then there’s the “accelerator hypothesis,” suggesting that both type 1 and type 2 diabetes result from insulin resistance and genetic background that affect the rate of beta cell loss and the disease phenotype. Dr. Sattar said that the accelerator hypotheses “makes complete sense to me. Because the population is so obese, we’re seeing it more now whereas we might not have seen it 40 years ago when the BMI differentials were far less in society.”
Dr. Twig has no disclosures. Dr. Sattar has consulted for or received lecture fees from Amgen, AstraZeneca, Boehringer Ingelheim, Eli Lilly, Hanmi Pharmaceutical, Merck Sharp & Dohme, Novartis, Novo Nordisk, Pfizer, and Sanofi, and received grant support from AstraZeneca, Boehringer Ingelheim, Novartis, and Roche Diagnostics through his institution.