Obesity, a major global health issue, has more than doubled since 1990, now affecting over 1billion people (1,2) . Conventional treatments, including drugs like orlistat, are often limited by side effects (3,4) . Onion ( Allium cepa ) peels, rich in quercetin and flavonoids, have shown promise in reducing obesity through improved lipid metabolism and antioxidant activity (5-7) . The dose-dependent efficacy of onion peel as a dietary supplement remains unclear, particularly when compared to standard drug treatments. Data on its effects on metabolic hormones like leptin and ghrelin, which regulate appetite and energy balance, are also limited. This study explores the effects of red and white onion peel extracts on obesity markers in high-fat diet-induced obese female rats. Acute toxicity test was done in both red and white onion peels, using Lorke’s method (8) in 18 Swiss albino mice with doses from 10–5000 mg/kg. No toxicity or mortality was observed, confirming the extracts are safe. Forty-eight female Wistar rats (average weight 120 g) were randomly assigned to eight groups (n = 6). Group 1 (normal control) received a standard pelleted diet, while obesity was induced in Groups 2–8 using a high-fat diet (HFD) for five weeks. After induction, Group 2 (obese control) was switched to a normal diet, while Groups 3–5 received HFD supplemented with 10%, 20%, or 30% red onion peel, and Groups 6–8 received HFD supplemented with 10%, 20%, or 30% white onion peel, respectively, for five weeks. At the end of the treatment period, parameters including obesity indices, fasting blood glucose (FBS), liver enzymes (AST, ALT, ALP), antioxidant markers (SOD, CAT, GSH, GPx), malondialdehyde (MDA), and hormones (leptin and ghrelin) were measured using standard procedures. Data analysis was performed using SPSS version 25, and results were presented with GraphPad Prism version 8. Statistical significance was considered at p < 0.05 using Dunnett’s multiple comparison test. Results from HFD-induced groups showed significant (p < 0.05) increases in obesity indices, FBS (6.09±0.29 mg/dl), TC (198.99±1.08mg/dl), TAG (144.78±1.03 mg/dl) LDL (130.23 ±2.03 mg/dl), MDA, leptin, and liver enzymes, with decreases in HDL (38.90 ± 4.22 mg/dl), ghrelin, and antioxidant enzyme activities. Red onion peel supplementation showed greater improvement than white onion peel in reducing obesity indices, FBS, cholesterol, MDA, leptin, and boosting antioxidant activity, indicating its higher therapeutic potency for managing obesity. Both onion-supplemented diets significantly reduced obesity indices, liver enzyme activities, and regulated fasting blood sugar (FBS), indicating anti-obesity potential. Notably, red onion peel showed a greater effect than white onion peel, particularly at higher concentrations, as evidenced by more pronounced improvements in antioxidant enzyme activities and reductions in leptin and malondialdehyde levels. These findings suggest that red onion peel may offer superior therapeutic benefits and could be more effective in the dietary management of obesity.
Edeke et al. (Fri,) studied this question.