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Glucose metabolism and insulin regulation are two of the body's most critical physiological processes and, at the same time, two of the most disrupted in modern societies: insulin is the body's main anabolic hormone, synthesized and secreted by the beta cells of the pancreas, which allows muscle, liver, and fat cells to take up glucose from the bloodstream and use it as fuel or store it; when this system fails (due to tissue resistance to insulin, exhaustion of pancreatic secretory capacity, or both), prediabetes and type 2 diabetes progressively appear, along with a set of cardiometabolic disturbances known as metabolic syndrome, which probably constitute the most relevant silent pandemic of the 21st century.
Type 2 diabetes does not appear overnight but after a process that can take decades: it begins with tissue resistance to insulin (muscle and liver cells respond less to the insulin signal to take up glucose); the pancreas compensates by secreting more insulin (compensatory hyperinsulinemia), which keeps blood glucose normal but already produces detectable metabolic alterations (metabolic syndrome, nonalcoholic fatty liver, atherogenic dyslipidemia); progressively the pancreatic beta cells become exhausted and hyperglycemia begins, first postprandial (prediabetes), then fasting (diabetes); by the time diabetes is diagnosed, there is usually already a 50-70% loss of beta-cell functional capacity and established cardiovascular damage to varying degrees.
Fasting blood glucose: normal below 100 mg/dL; prediabetes 100-125; diabetes ≥126 (confirmed on two occasions).
Glycated hemoglobin (HbA1c): reflects average blood glucose over the previous 2-3 months; normal below 5.7%; prediabetes 5.7-6.4%; diabetes ≥6.5%. A less sensitive marker for early detection because it rises late in the cascade.
Fasting insulin and HOMA-IR: elevated baseline insulin with normal blood glucose is an early marker of insulin resistance, preceding prediabetes. HOMA-IR above 2.5 suggests significant resistance.
Oral glucose tolerance test: blood glucose 2 hours after 75 g of oral glucose; identifies intolerance that fasting glucose may not detect.
High triglycerides + low HDL + large waist circumference: a clinical triad suggesting metabolic syndrome/insulin resistance without the need for specific testing.
The good news is that the cascade toward type 2 diabetes is highly reversible in its early phases (insulin resistance, prediabetes) and partially reversible even in early established diabetes:
Weight loss: the intervention with the best clinical backing. Losses of 7-10% of body weight in people with prediabetes reduce progression to diabetes by approximately 60% (DPP study). Larger losses (15-20% with bariatric surgery or intensive programs such as DiRECT) can produce complete remission of type 2 diabetes in a significant proportion of cases.
Regular physical exercise: a combination of moderate-to-intense aerobic exercise + strength training; active skeletal muscle is the main organ that takes up glucose.
Mediterranean diet: supported by PREDIMED and other trials for preventing type 2 diabetes in people at risk.
Diets low in refined carbohydrates: including supervised ketogenic diets in some clinical contexts, with growing data on diabetes remission.
Adequate and regular sleep: chronic sleep deprivation produces acute insulin resistance.
Smoking cessation: tobacco worsens insulin resistance.
Several supplements have modest but documented clinical backing for improving glycemic control, as a complement to lifestyle interventions:
Metformin remains the first-line drug in type 2 diabetes because of its safety profile, efficacy, cost, and possible pleiotropic benefits for longevity (TAME study ongoing). In recent decades, new drug classes have appeared (GLP-1 agonists such as semaglutide or liraglutide, SGLT-2 inhibitors such as empagliflozin, others) with documented cardiovascular and renal benefits that have changed the treatment paradigm for type 2 diabetes.
The epidemic of insulin resistance and type 2 diabetes is probably the most prevalent and most preventable metabolic pathology of the 21st century; lifestyle interventions (healthy weight, regular exercise, a Mediterranean or low-ultra-processed diet, adequate sleep) have effect sizes comparable to or greater than pharmacological ones in prevention and early reversal; supplements are useful complements with modest expectations; medical follow-up is essential once the cascade is established.
Information, not medical advice.