Elevated fasting insulin concentrations above approximately 46 pmol/L are associated with partial suppression of lipolysis and increased risk of adipose tissue expansion in non-obese adults, indicating that insulin's antilipolytic effect occurs at concentrations lower than those required for glucose uptake.

When insulin levels rise above 46 pmol/L, fat cells stop breaking down stored fat, even if blood sugar is normal. This happens because insulin binds to receptors on fat cells and turns off the enzymes that release fat for energy. The fat stays stored, and over time, the fat tissue grows larger. This effect starts at much lower insulin levels than what’s needed to lower blood sugar, so fat storage can increase before glucose control is affected.