Effects of intermittent fasting combined with a ketogenic diet versus a hypocaloric diet on metabolic outcomes in adults with type 2 diabetes mellitus: A controlled clinical study

Abstract

Background

Type 2 diabetes mellitus (T2DM) continues to rise globally, highlighting the need for effective and sustainable dietary strategies. Intermittent fasting (IF) and ketogenic diets have been associated with metabolic adaptations such as enhanced fat oxidation, ketone body production, and improved insulin sensitivity; however, evidence on their combined implementation in clinical settings remains limited.

Objective

To evaluate the associations of three dietary strategies—IF combined with a ketogenic diet (IF + KD), a hypocaloric diet (HD), and a control group (CG)—with anthropometric, metabolic, behavioral, and quality-of-life outcomes in adults with T2DM.

Methods

A 12-week controlled, parallel-group clinical study was conducted in 30 adults with T2DM allocated to IF + KD (n = 10), HD (n = 10), or CG (n = 10). The IF + KD group followed a structured 16:8 IF protocol combined with a ketogenic diet, while the HD group received an individualized energy-restricted diet. Anthropometric, biochemical, physical activity, and quality-of-life measures were assessed at baseline and week 12.

Results

Reductions were observed in body weight, body mass index, waist circumference, and body fat percentage (all p < 0.05). HbA1c decreased in both IF + KD and HD groups, and total cholesterol was reduced without adverse changes in renal function. Physical activity and quality-of-life scores improved in intervention groups, with minimal variation in the CG.

Conclusion

IF + KD and HD were associated with short-term improvements in metabolic and anthropometric outcomes in adults with T2DM. Findings provide real-world evidence on combined dietary strategies and should be interpreted within the context of a non-randomized design.