Background/Objectives: Obesity is a worldwide health problem, and adopting a diet is one of the main factors to enhance weight loss and manage obesity implications. However, the recommendation of a certain diet remains controversial. We aimed to compare the hepatic and metabolic effects of both high-protein diet (HPD) and ketogenic diet (KD) in a rat model of obesity. Methods: This study included 40 adult male albino rats, which were divided into four groups: group I, control group with a normal diet; group II, obese treated with high-fat diet; group III, obese treated with HPD; and group IV, obese treated with KD. Measurements of the lipid profile, glucose, and insulin serum levels and liver function tests were performed by examining the liver parenchyma for histopathology and oxidative stress (OS) markers. Results: High serum levels of glucose, insulin, and lipid profile and homeostasis model assessment of insulin resistance index were observed in the KD group compared with those in the other groups, with high levels of liver enzymes and OS markers and tumor necrosis factor in the hepatic tissue (p < 0.05). On the other hand, the HPD showed improved metabolic parameters and liver function with a low expression of OS markers in the hepatic tissue. Conclusion: These findings showed that HPD can be recommended as an effective weight loss diet with regard to its metabolic and hepatic effects. However, further clinical investigations are required to determine other HPD effects in obese patients.