Dr Doris Maugg
March 05, 2025
Patients with type 1 diabetes (T1D) who have risk factors such as obesity and hypertension can develop insulin resistance over time, a characteristic typically associated with type 2 diabetes (T2D). This condition, known as double diabetes, combines the characteristics of T1D and T2D.
“About a quarter of patients with T1D develop metabolic syndrome,” said Thomas Haak, MD, chief physician at the Diabetes Center Bad Mergentheim, Bad Mergentheim, Germany, and former president of the German Diabetes Society (DDG), speaking at the “Innere Medizin fachübergreifend — Diabetologie grenzenlos” congress held on February 7 and 8 in Munich, Germany.
“Double diabetes exists and requires appropriate treatment,” said Haak.
Patients with T1D often have elevated triglyceride levels and high blood pressure, with women affected more often than men. This combination doubles the risk for coronary heart disease and increases the risk for stroke, diabetic foot, and nephropathy.
Patients with T1D must take insulin throughout their lives to manage their blood glucose levels. Haak explained that the first sign of insulin resistance in T1D is an increased insulin requirement exceeding 100 units/d.
Diagnosis involves assessing the clinical presentation of T1D, measuring C-peptide levels in the blood, and considering family history. Relevant clinical parameters include obesity, body mass index (BMI), waist circumference, and metabolic syndrome, particularly triglyceride levels and hypertension.
According to the 2023 S3 guideline of the DDG on T1D management, more than half of patients with T1D have a BMI > 25. The prevalence of metabolic syndrome in this population is increasing, mirroring trends observed in the general population.
Complications and Risks
A 2016 German study examined more than 30,000 individuals with T1D for signs of metabolic syndrome and its complications. The findings revealed that 1 in 4 patients met the criteria for metabolic syndrome, defined by obesity, high blood pressure, and dyslipidemia, and could be classified as having double diabetes.
These patients had higher rates of micro- and macrovascular comorbidities, regardless of the glycemic control. The DDG guidelines recommend addressing each component of metabolic syndrome in patients with T1D.
Treatment: What Works, What Does Not?
“So how do we best manage this condition?” asked Haak. A 2024 consensus report from the American Diabetes Association identified three key strategies:
- Lifestyle changes, such as high-fiber diets
- Bariatric surgery
- Medication
Haak emphasized that dietary adjustments are an effective method, focusing on reducing fat and carbohydrate intake. He highlighted the effectiveness of an initial 12-day “liver fast,” a protein-restricted diet that helps improve metabolic parameters.
Short-term dietary interventions, such as two consecutive “oat days” during which only oats are consumed, are beneficial for insulin resistance.
In clinical practice, combining dietary interventions with glucagon-like peptide 1 receptor agonists (GLP-1 RAs) has yielded promising results. However, Haak noted that timing is critical due to the potential for gastrointestinal side effects associated with GLP-1 RAs.
While bariatric surgery can be effective for obesity in T1D, it carries a risk for complications and requires careful patient selection as well as psychological and medical follow-up.
Metformin is effective for glycemic control but is not indicated for T1D alone, Haak continued. However, metformin can be used in patients with T1D and T2D. “Metformin should definitely be included in the concept,” he said, though it is not suitable for long-term use due to the risk for hypoglycemia.
The DDG guidelines highlight the role of metformin in managing insulin resistance in patients with T1D.
SGLT2 Inhibitors: A No-Go
For patients with well-controlled T1D, GLP-1 RAs can be used to manage obesity and insulin resistance, Haak explained. However, caution is required due to the increased risk for diabetic ketoacidosis. While these medications are not contraindicated, their costs are not reimbursed in many healthcare systems.
Haak referenced findings from the DEPICT-1 study, which showed that sodium-glucose cotransporter 2 (SGLT2) inhibitors in T1D can lower insulin requirements and reduce hypoglycemia risk but are also linked to ketoacidosis and other adverse events.
“SLGT2 inhibitors are contraindicated in T1D; the risk is too high,” Haak said, noting the available alternative treatments.
The guidelines do not confirm the safety and efficacy of SGLT2 inhibitors as an add-on treatment for T1D due to inconsistent results. Further studies are required to evaluate their safety.
This story was translated from Medscape’s German edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
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