Metabolic and Orexin-A Responses to Ketogenic Diet and Intermittent Fasting: A 12-Month Randomized Trial in Adults with Obesity.

The ketogenic diet produced the largest sustained reductions in BMI, fat mass, fasting glucose, and total cholesterol over 12 months.

• 30 adults with obesity (BMI ≥ 30 kg/m²) were randomized 1:1:1 to three dietary arms (n=10 per group)
• The trial lasted 12 months with assessments at baseline and every 3 months
• All 30 participants completed the intervention (100% completion rate)
• Between-group differences remained significant for fat mass and glucose trajectories after correction for multiple comparisons

TRF16:8 elicited more rapid early metabolic improvements and showed the most consistent longitudinal increase in Orexin-A levels.

• The 16:8 time-restricted eating regimen involved an eating window restricted to 8 hours per day
• TRF16:8 showed faster early responses compared to ketogenic diet and ADF5:2
• Between-group differences remained significant for Orexin-A trajectories after correction for multiple comparisons
• The most stable enhancement in Orexin-A levels was observed in the TRF16:8 group across the 12-month period

The ADF5:2 intermittent fasting protocol resulted in moderate improvements across metabolic outcomes.

• The 5:2 protocol involved 5 days of normal eating and 2 days of fasting or severe caloric restriction per week
• ADF5:2 improvements were intermediate between those of the ketogenic diet and TRF16:8
• Outcomes assessed included BMI, body composition, fasting glucose, lipid profile, and inflammatory cytokines

Increases in Orexin-A were associated with markers of improved metabolic flexibility and reduced inflammation across all dietary groups.

• Inflammatory markers assessed included CRP, IL-6, TNF-α, and IL-10
• Plasma Orexin-A levels were measured at baseline and every 3 months over the 12-month trial
• The authors note that 'mediation analyses were exploratory and non-causal,' meaning no causal relationship between Orexin-A and metabolic outcomes was established
• Orexin-A is described as 'a peptide implicated in energy regulation'

Dietary adherence was monitored through structured logs and monthly assessments across all three intervention arms.

• Structured dietary logs were used to monitor adherence throughout the 12-month trial
• Monthly assessments were conducted in addition to the formal measurement timepoints every 3 months
• Statistical analyses included repeated-measures models with sensitivity analyses adjusted for age and sex

The small sample size of 30 participants limits the generalizability of the findings.

• Only 10 participants were assigned to each of the three dietary arms
• The authors state 'results should be interpreted cautiously' given the small sample size
• Larger trials are warranted to clarify the role of Orexin-A as a potential biomarker of dietary response in obesity
• The long-term neuroendocrine effects of these dietary strategies are described as 'poorly understood' in the existing literature