Indian Study Confirms Lean Diabetes as High-Risk Type 2 Diabetes Phenotype with More Microvascular Complications
India: A large-scale study published in Diabetes Research and Clinical Practice has challenged the notion that lean diabetes is a distinct form of the disease, suggesting instead that it represents one end of the type 2 diabetes (T2D) spectrum. The research, led by Dr. Viswanathan Mohan from the Department of Diabetology, Madras Diabetes Research Foundation, and Dr. Mohan’s Diabetes Specialities Centre, Chennai, examined the prevalence, clinical characteristics, and complication patterns in individuals with lean diabetes to determine whether it stands apart as a separate entity.
The study analysed electronic health records of 398,258 individuals with type 2 diabetes attending a tertiary care diabetes centre in South India. Patients were classified into five categories based on body mass index (BMI): 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). Among them, lean diabetes accounted for 1.5% of cases (n = 5,865).
The following were the notable findings of the study:
- Individuals with lean diabetes were diagnosed at a younger age and showed a male predominance.
- They had poorer glycemic control with higher fasting and postprandial plasma glucose as well as elevated HbA1c levels than other type 2 diabetes groups.
- These patients exhibited significantly lower C-peptide levels, indicating pronounced insulin deficiency.
- Serum cholesterol levels were lower in lean diabetes patients than in other BMI categories.
- The study revealed a higher prevalence of microvascular complications in this group, with retinopathy in 42% of patients.
- Nephropathy was present in 39% of lean diabetes patients.
- Neuropathy affected 73% of individuals with lean diabetes, a rate significantly higher than in other T2D groups.
- More than half of lean diabetes patients (55.6%) were treated with insulin, a higher proportion compared to other BMI-based categories.
According to the authors, these findings suggest that lean diabetes is not a separate disease type but a severe, insulin-deficient phenotype within the T2D spectrum. The combination of younger age of onset, poor glycemic profiles, and increased complication rates highlights the need for early diagnosis and aggressive management in this subgroup.
Dr. Mohan and colleagues emphasised that this is the largest study to date examining lean diabetes in a South Indian population, providing critical insights into its clinical profile. The results underscore the heterogeneity of T2D and the importance of considering BMI-related phenotypes when designing treatment strategies.
The study also has significant clinical implications. Given the high prevalence of microvascular complications and the reliance on insulin therapy, lean diabetes patients require close monitoring and early intervention to prevent long-term morbidity. The authors call for increased awareness among clinicians to identify this subgroup promptly and tailor management accordingly.
The authors conclude, "The research highlights that lean diabetes should not be considered a distinct form of diabetes but rather an extreme presentation within type 2 diabetes, marked by severe insulin deficiency and heightened complication risk. These findings reinforce the need for individualized treatment approaches and further research into the underlying mechanisms driving this phenotype."
Reference:
Mohan, V., Pramodkumar, T. A., Deepa, M., Pradeepa, R., Unnikrishnan, R., Routray, P., Tharunika, S., Lakshmi, N., Killivalavan, D., Ganesan, S., Jebarani, S., Venkatesan, U., Das, S., & Anjana, R. M. (2025). Lean diabetes is one end of the spectrum of type 2 diabetes and not a separate entity. Diabetes Research and Clinical Practice, 227, 112387. https://doi.org/10.1016/j.diabres.2025.112387
