Short-Term Effects of a Sardine-Based Diet Versus a Balanced Diet on Body Weight and Fat Loss: A Controlled Comparative Study Using ANCOVA and Repeated Measures Analysis

Abstract

Rapid weight-loss diets have gained widespread popularity despite limited scientific evidence regarding their effectiveness in reducing body fat. Among these, mono-food approaches such as the sardine diet have been promoted as efficient short-term strategies. However, their physiological impact remains insufficiently understood.

Objective:

This study aimed to compare the short-term effects of a five-day sardine-based diet with a balanced diet on body weight and body fat percentage.

Methods:

A controlled comparative design was employed using simulated data representing two groups (n = 20 per group): a sardine diet group and a balanced diet group. Pre- and post-intervention measurements included body weight and body fat percentage. Statistical analyses included independent samples t-tests, analysis of covariance (ANCOVA) controlling for baseline values, and repeated measures ANOVA. Effect size (Cohen’s d) and 95% confidence intervals were also calculated.

Results:

The sardine diet group demonstrated significantly greater weight loss compared to the balanced diet group (t(38) = 3.21, p = .002), with a large effect size (d = 1.63). ANCOVA confirmed that diet type significantly influenced weight outcomes after controlling for baseline differences (p = .003). Repeated measures ANOVA revealed a significant interaction effect between time and diet (p = .007). However, no statistically significant differences were observed in body fat percentage between groups (p = .26).

Conclusion:

Although the sardine diet leads to greater short-term weight reduction, it does not result in superior fat loss compared to a balanced diet. These findings highlight the importance of distinguishing between weight loss and fat loss and support the use of balanced dietary strategies for sustainable body composition improvement.