The Impact of a ketogenic diet (KD) vs. a Low-Fat Diet (LFD) on weight loss in overweight and obese women: A Randomized Crossover Trial

Abstract:

Background: The global prevalence of obesity and overweight is a major public health concern, linked to increased risks of cardiovascular disease and metabolic disorders. Dietary interventions, such as the ketogenic diet (KD) and the low-fat diet (LFD), are popular strategies for weight management. However, their comparative effectiveness, especially in specific populations like women in Yemen, remains underexplored.

Objective: This study aimed to compare the effects of a KD and an LFD on weight loss, body composition, and key biochemical markers in overweight and obese women over a 12-week period.

Methods: We conducted a 12-week randomized crossover trial with 20 overweight and obese women in Sana'a, Yemen. Participants were randomly assigned to either a KD (65% fat, 25% protein, 10% carbs) or an LFD (30% fat, 15% protein, 55% carbs), with both diets being isocaloric (1650 calories). We measured anthropometric parameters (body weight, BMI, waist and hip circumference), body composition (fat mass, fat-free mass), and a range of biochemical markers (blood glucose, lipid profile, urea, creatinine, calcium, vitamin D, and ketone bodies) at baseline and weekly intervals.

Results: Both diets led to significant decrease (p < 0.001) in body weight, body mass index, and percentage of body fat, and an increase in muscle mass. The KD group, however, experienced more rapid weight loss (averaging 2 kg/week) compared to the LFD group (1 kg/week). The KD also resulted in more favorable changes to the lipid profile, including decrease in total cholesterol, LDL-C, and triglycerides but not significant, and an increase in HDL-C. Both diets maintained stable creatinine and urea levels. A key finding was the significant decrease in Vitamin D and calcium levels in the KD group, whereas the LFD group maintained these levels. The KD successfully induced a state of nutritional ketosis, evidenced by a significant and sustained increase in ketone body levels.

Conclusion: Both a ketogenic diet and a low-fat diet are effective for weight loss and improving cardiovascular risk factors in overweight and obese women. The ketogenic diet demonstrated a greater and more rapid impact on weight loss and lipid profile improvements, while the low-fat diet was more effective at preserving vitamin D and calcium. These findings highlight that both caloric restriction and macronutrient composition are important in managing obesity.