Lean diabetes is one end of the spectrum of type 2 diabetes and not a separate entity

Lean diabetes mellitus is non-type 1 diabetes with BMI < 18.5 kg/m² and is now proposed to be a unique form of diabetes. We report on prevalence, clinical and microvascular complication profile in lean diabetes to see whether it stands out as a distinct entity or is a continuum of type 2 diabetes (T2D).

Using electronic records of a tertiary care diabetes centre in South India, individuals with T2D(n = 398,258) were classified using BMI, as lean(<18.5 kg/m²), normal weight(18.5-22.9 kg/m²),overweight(23.0-24.9 kg/m²),mildly obese(25.0-29.9 kg/m²), and markedly obese(≥30.0 kg/m²) T2D. Clinical and biochemical features as well as frequency of microvascular complications of lean diabetes were compared with other T2D groups.

The prevalence of lean diabetes was 1.5 %(n = 5865). Lean diabetes were younger with male preponderance, had higher fasting, postprandial plasma glucose, HbA1c levels, lower C-peptide and serum cholesterol compared to normal weight, overweight and obese T2D. Lean T2D had higher prevalence of retinopathy (42%), nephropathy (39 %), and neuropathy (73 %) compared to other groups(p < 0.001). Additionally, lean T2D were more likely to be treated with insulin (55.6 %, p < 0.001) compared with other groups.

Lean diabetes is one end of the spectrum of T2D and is characterized by an earlier age of onset, more severe insulin deficiency and increased risk of microvascular complications.