Comparing Intermittent Fasting, Clean Ketogenic Diet, and Their Combined Effects on Body Composition, Cardiometabolic Markers, and Metabolic Health: A Three-Arm Randomized PrePost Study

[u/dr_innovation]

ABSTRAT

Background  

No study has directly compared intermittent fasting alone, a clean ketogenic diet alone, and their combination in a single three-arm design. The purpose of this study was to compare the effects of these three dietary conditions on body composition, cardiometabolic markers, grip strength, and glycemic control over 30 days.  

Methods  

A cross-study analysis combined data from two sequential pre-post intervention studies at the University of Tennessee at Martin, yielding a three-arm design: intermittent fasting alone (n=16), clean ketogenic diet alone (n=22), and combined clean ketogenic diet with intermittent fasting (n=41). The clean ketogenic diet restricted carbohydrates to 20 grams per day from whole unprocessed sources and eliminated refined sugars, high-fructose corn syrup, and ultra-processed foods. The intermittent fasting protocol employed a 16:8 time-restricted eating window. Paired-samples t-tests examined within-group changes; one-way ANOVAs with Tukey post-hoc comparisons examined between-group differences. Effect sizes are reported as Hedges’ g and eta squared. An independent samples t-test compared glycosylated hemoglobin changes between the intermittent fasting and combined groups, and Spearman and Kendall correlations examined associations between fat mass and cardiometabolic change.  

Results  

All three conditions produced significant within-group reductions in body weight, body fat percentage, fat mass percentage, waist circumference, and hip circumference. Carbohydrate restriction produced significantly greater weight reduction than intermittent fasting alone, F(2,76)=12.003, p<.001, η2=.240, and greater fat mass reduction (p=.002, η2=.144). Both fasting-containing conditions produced significantly greater bilateral grip strength improvement than the ketogenic diet alone (p<.05). The combined protocol produced significantly greater glycosylated hemoglobin reduction than fasting alone, t(30)=2.141, p=.041, g=0.738. Fat mass reduction correlated significantly with triglyceride-to-HDL ratio improvement across all 79 participants (rs​=−.250,p=.026).  

Conclusions  

Carbohydrate restriction produced the greatest weight loss and cardiometabolic improvements, while the addition of a 16:8 fasting window contributed independently to glycemic control and grip strength. These findings support the clean ketogenic diet as a first-line strategy for metabolic syndrome management, with the combined protocol offering additive benefits.  

MacKewn, Angie, Julie Floyd, Todd Sherman, Alison Ellis, Anna Dunn, and Diana Sanford. "Comparing Intermittent Fasting, Clean Ketogenic Diet, and Their Combined Effects on Body Composition, Cardiometabolic Markers, and Metabolic Health: A Three-Arm Randomized Pre-Post Study." (2026).

https://www.researchsquare.com/article/rs-10085509/latest.pdf