Causes of Type 1 Diabetes

Type 1 diabetes is based on an autoimmune mechanism: T-lymphocytes attack and destroy the beta cells of the pancreas. Genetics plays a significant role — particularly the HLA gene region (HLA-DRB1, -DQA1, -DQB1). Heritability is estimated at 0.69–0.88, yet the concordance rate even among identical twins is only 30–70% — meaning genes alone don't fully determine the disease. Possible triggers mentioned in the literature for genetically predisposed people include viral infections and certain early-life factors, although their causal role hasn't been conclusively proven.

According to the CDC, type 1 diabetes is not caused by diet or lifestyle, and there is currently no known way to prevent it.

Causes & Risk Factors of Type 2 Diabetes

Type 2 diabetes develops through a combination of insulin resistance and a gradual decline in insulin production. The main risk factors identified by researchers include:

  • Excess weight and obesity — a body mass index above 30 is often cited as an approximate threshold for elevated risk; the contribution of excess weight to the disease ranges from ~30% (in people of East Asian descent) to nearly 100% (in some Indigenous populations);
  • Physical inactivity — fewer than 3 workouts a week is associated with higher risk;
  • Abdominal obesity — a waist circumference above roughly 102 cm in men and 89 cm in women is sometimes used as a reference point;
  • Dietary factors — sugary drinks and excess saturated and trans fats raise risk, while polyunsaturated and monounsaturated fats are linked to lower risk in studies; in some Asian populations, excessive white rice consumption is also associated with higher risk;
  • Heredity — estimated at 47–77%; more than 36 genes and 80 polymorphisms linked to risk are known;
  • Age 45 and older, a family history of type 2 diabetes, and a prior episode of gestational diabetes;
  • Coexisting conditions — high blood pressure, lipid disorders, and non-alcoholic fatty liver disease;
  • Smoking — associated with a higher risk of both diabetes itself and its complications;
  • Belonging to certain ethnic groups — according to the CDC, higher risk is noted among African Americans, Hispanic/Latino Americans, American Indians, and Alaska Natives.

Less Obvious Factors

Research also links adverse childhood experiences (abuse, neglect, family dysfunction) to approximately a 32% higher likelihood of developing type 2 diabetes in adulthood, with neglect showing the strongest association. Certain medications — some antipsychotics, as well as SSRIs/SNRIs — are associated with metabolic side effects that may increase risk. Chronic psychological stress and insufficient sleep are also among the factors mentioned in the literature.

Having one or more risk factors doesn't mean the disease will necessarily develop, and their absence doesn't guarantee protection from it. Only a doctor can assess your personal risk.