Background: The notion that specific exercises reduce localized adipose tissue depots (i.e., targeted fat loss) and modify fat distribution is commonly termed spot reduction. According to this long-held popular belief, exercising a limb would lead to greater reduction in the adjacent adipose tissue in comparison to the contralateral limb. Aside from popular wisdom, scientific evidence from the 20th and 21th century seems to offer inconclusive results. Objective: To summarize the peer-reviewed literature assessing the effects of unilateral limb training, compared to the contralateral limb, on the localized adipose tissue depots on healthy participants, and to meta-analyse its results. Methods: We followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). We searched PubMed, Web of Science, and SCOPUS electronic databases, using several relevant keywords combinations. Independent experts were contacted to help identify additional relevant articles. Following a PICOS approach, we included controlled studies that incorporated a localized exercise intervention (i.e., single-limb training) to cohorts of healthy participants (i.e., no restriction for fitness, age, or sex), compared to a control condition (i.e., contralateral limb), where the main outcome was the pre-to-post intervention change of localized fat. The methodological quality of the studies was assessed using the Physiotherapy Evidence Database scale. Pre- and post-intervention mean ± standard deviation for fat-related outcome from the trained and control groups (limbs) were converted to Hedges’ g effect size (ES; with 95% confidence intervals [CI]), using a random-effects model. The impact of heterogeneity was assessed using the I2 statistic. The risk of reporting bias was explored using the extended Egger’s test. The statistical significance threshold was set at p < 0.05. Results: From 1,833 search records initially identified, 13 were included in the meta-analysis, involving 1,158 male and female participants (age, 14-71 years). The 13 studies achieved a high methodological quality, and results with low heterogeneity (I2 = 24.3%) and no bias (Egger’s test p = 0.133). The meta-analysis involved 37 comparisons, with 17 of these favouring (i.e., greater reduction of localized fat) the trained limb, and 20 favouring the untrained limb, but the ES ranged between -1.21 to 1.07. The effects were consistent, with a pooled ES = -0.03, 95% CI -0.10 to 0.05, p = 0.508, meaning that spot reduction was not observed. Conclusion: Localized muscle training has no effect on localized adipose tissue depots, i.e., no spot reduction, regardless of the characteristics of the population and of the exercise program. The popular belief on spot reduction is probably derived from wishful thinking, and convenient marketing strategies, such as influencers seeking increased popularity and procedures’ sellers interested in increasing advertising.