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Impact of a very low-calorie ketogenic diet on metabolic and microbiota outcomes in post-bariatric patients and bariatric-Naïve individuals: A comparative pilot study.

Diabetes, obesity & metabolism
April 1, 2025
Ilaria Ernesti et al. (13 authors)
Journal ArticleComparative StudyHuman Study
Study Details

Study Goal

The researchers aimed to compare the efficacy and safety of a very low-calorie ketogenic diet (VLCKD) in post-bariatric surgery patients with weight regain versus bariatric surgery-naïve patients.

Results Summary

Both groups achieved significant weight loss, with the post-bariatric group showing slightly less metabolic improvement. The VLCKD also led to significant changes in gut microbiota composition, with more pronounced effects in the surgery-naïve group. Mild renal function changes were noted in post-bariatric patients but remained within acceptable ranges.

Population

Post-bariatric surgery patients with weight regain (BS+) and bariatric surgery-naïve patients (BS-).

Effective Dosage

Not specified

Duration

8 weeks

Interactions

None mentioned

Extracted Claims (10)
InterventionDirectionEndpointPopulationDosageImpactClaim #
very low-calorie ketogenic diet (VLCKD)
decrease
weight loss
patients with weight regain post-bariatric surgery (BS+)
-6.9%
achieved significant weight loss
#1
very low-calorie ketogenic diet (VLCKD)
decrease
weight loss
bariatric surgery-naïve patients (BS-)
-8.3%
achieved significant weight loss
#2
very low-calorie ketogenic diet (VLCKD)
increase
metabolic improvement
patients with weight regain post-bariatric surgery (BS+)
slightly less
showed slightly less metabolic improvement
#3
very low-calorie ketogenic diet (VLCKD)
decrease
insulin resistance
patients with weight regain post-bariatric surgery (BS+)
slightly less
showed slightly less metabolic improvement
#4
very low-calorie ketogenic diet (VLCKD)
decrease
triglycerides
patients with weight regain post-bariatric surgery (BS+)
slightly less
showed slightly less metabolic improvement
#5
very low-calorie ketogenic diet (VLCKD)
change
gut microbiota (GM) composition
patients with weight regain post-bariatric surgery (BS+)
significant changes
led to significant changes
#6
very low-calorie ketogenic diet (VLCKD)
change
gut microbiota (GM) composition
bariatric surgery-naïve patients (BS-)
significant changes
led to significant changes
#7
very low-calorie ketogenic diet (VLCKD)
increase
microbial diversity
bariatric surgery-naïve patients (BS-)
more pronounced
were more pronounced
#8
very low-calorie ketogenic diet (VLCKD)
change
specific taxonomic shifts
bariatric surgery-naïve patients (BS-)
more pronounced
were more pronounced
#9
very low-calorie ketogenic diet (VLCKD)
change
mild renal function changes
patients with weight regain post-bariatric surgery (BS+)
mild
were noted
#10
Abstract

AIMS: To date, bariatric surgery (BS) is the most effective long-term treatment for obesity, but weight regain (WR) is common. The very low-calorie ketogenic diet (VLCKD) is effective for weight loss and may influence gut microbiota (GM) composition, but it has been scarcely evaluated in post-bariatric patients. This study compared the efficacy and safety of a VLCKD in patients with WR post-bariatric surgery (BS+) and in bariatric surgery-naïve patients (BS-). METHODS: In this prospective, case-control study, 33 patients (15 BS+, 18 BS-) underwent an 8-week-long VLCKD. Outcomes included weight loss, metabolic profile, safety and GM composition. RESULTS: Both groups achieved significant weight loss (BS+: -6.9%, BS-: -8.3%), but the BS+ group showed slightly less metabolic improvement, particularly in insulin resistance and triglycerides. GM composition differed at baseline, reflecting the lasting effects of BS, and VLCKD led to significant changes in both groups. Microbial diversity and specific taxonomic shifts were more pronounced in BS- patients. Mild renal function changes were noted in BS+ patients, though these remained within clinically acceptable ranges. CONCLUSION: VLCKD is effective in both BS+ and BS- patients, though metabolic and microbial responses may be less robust post-surgery, possibly due to anatomical and physiological changes. Tailored approaches may be therefore needed to optimize outcomes in post-bariatric patients.

Medical Subject Headings (MeSH)
HumansDiet, KetogenicPilot ProjectsFemaleMaleBariatric SurgeryMiddle AgedAdultGastrointestinal MicrobiomeProspective StudiesWeight LossCase-Control StudiesTreatment OutcomeCaloric RestrictionObesity, MorbidObesity
Study Links
Quality Scores
Safety80
Efficacy85/10
Quality75/10
Citation Metrics
Total Citations1
Citations/Year1.0
Research Impact Scores
APT Score0.50
Weight Score2.67
Normalized Score0.81
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