Insulin resistance is the reduced ability of cells, primarily in muscle, liver, and adipose tissue, to respond to insulin. It drives the pancreas to produce more insulin to achieve the same blood glucose control, leading to chronically elevated insulin levels, progressive beta-cell fatigue, and eventually type 2 diabetes. It is also a powerful driver of the body composition changes that characterise middle age.
What Drives Insulin Resistance
- Excess visceral adiposity: fat surrounding the organs is hormonally active and produces inflammatory cytokines that directly interfere with insulin receptor signalling
- Inactivity: skeletal muscle is the largest insulin-sensitive tissue in the body. Muscle contraction independently of insulin drives glucose uptake. Inactivity reduces both insulin sensitivity and the non-insulin-mediated glucose uptake that muscle provides
- Poor sleep: a single night of poor sleep reduces insulin sensitivity by 30 to 40 percent through multiple hormonal mechanisms
- Dietary pattern: high intake of refined carbohydrates and ultra-processed foods maintains postprandial insulin spikes that downregulate insulin receptor sensitivity over time
- Chronic stress: cortisol counteracts insulin action and promotes hepatic glucose production
The Most Effective Interventions for Reversal
Resistance training is the most powerful single intervention for improving insulin sensitivity, because it builds muscle tissue that then acts as a glucose sink independently of insulin. Even a single resistance training session improves insulin sensitivity for 24 to 72 hours. Aerobic exercise produces smaller but complementary improvements. Combined with a lower-carbohydrate, higher-protein dietary pattern and sleep optimisation, insulin resistance is highly reversible in most adults who do not yet have established type 2 diabetes.