Research on the benefits of apple cider vinegar has tended to focus on its hypoglycemic effects and lipid profile changes during long-term consumption, without exploring its acute effects on oxidative stress during short-term consumption. Therefore, this study aimed to determine whether apple cider vinegar consumption affects postprandial plasma MDA levels in obese adults. The hypothesis of this study is that apple cider vinegar consumption has an acute effect on changes in postprandial plasma MDA levels in obese adult subjects.

Subject criteria are adults aged 19-59 years; obese nutritional status; based on a BMI of ≥ 25.0 kg/m² (according to the Asia-Pacific classification); in good general health. Exclusion criteria include pregnancy, breastfeeding, and menopause; consuming alcohol; intolerance to apple cider vinegar or fermented products.

This preliminary study, a parallel, randomized, open-label, controlled clinical trial, compared two groups: a control group receiving a standard diet without apple cider vinegar, and an intervention group receiving a standard diet with a single dose of apple cider vinegar.

This preliminary study is designed as a parallel, randomized, open-label, controlled clinical trial to evaluate the acute effect of apple cider vinegar (ACV) on postprandial oxidative stress in adults with obesity.

Obesity is strongly associated with increased oxidative stress and enhanced lipid peroxidation, particularly in the postprandial state. Malondialdehyde (MDA) is a widely used biomarker of lipid peroxidation and reflects oxidative damage to cell membranes. Postprandial increases in MDA may contribute to cardiometabolic risk. Apple cider vinegar contains acetic acid and bioactive compounds that may modulate postprandial metabolic responses and potentially attenuate oxidative stress. However, clinical evidence regarding its acute effect on postprandial lipid peroxidation in adults with obesity remains limited.

Eligible participants will be randomly assigned to either a control group (standard meal without ACV) or an intervention group (single dose of ACV prior to a standardized meal). The intervention consists of 15 mL of apple cider vinegar diluted in 250 mL of water, consumed within 5 minutes. The control group will receive 250 mL of water under identical conditions. Fifteen minutes after beverage consumption, participants will consume a standardized meal within 30 minutes.

To minimize confounding factors affecting oxidative stress, participants will undergo a one-week run-in period during which they will receive balanced diet education and be instructed to avoid antioxidant supplements and unusual strenuous physical activity. Additional dietary and lifestyle restrictions will be applied 24 hours prior to the intervention. Participants will fast overnight (10:00 PM-8:00 AM) before the study visit.

Venous blood samples will be collected in the fasting state (baseline) and 3 hours after meal consumption to assess changes in plasma malondialdehyde concentration. Lipid peroxidation will be quantified using high-performance liquid chromatography (HPLC) analysis of MDA-thiobarbituric acid (TBA) adducts.

The required sample size was calculated using a two-group comparison formula with an additional allowance for potential dropout. Participants who do not comply with beverage or meal consumption requirements will be excluded from per-protocol analysis.

This study aims to determine whether a single pre-meal dose of apple cider vinegar can attenuate postprandial lipid peroxidation in adults with obesity and provide evidence for its potential role as a simple dietary strategy to reduce oxidative stress.

Inclusion Criteria:

1. Adults aged 19-59 years.
2. Obese, based on a BMI of ≥ 25.0 kg/m² (according to the Asia-Pacific classification).
3. In good general health.
4. No diagnosed chronic diseases (e.g diabetes mellitus, heart disease, kidney disease, cancer, hepatitis, or chronic infections).
5. Willing to participate in the entire study and sign an informed consent form.

Exclusion Criteria:

1. Pregnant, breastfeeding, or menopausal women.
2. Alcohol consumption.
3. Intolerance to apple cider vinegar or fermented products.