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128ANALESRANFwww.analesranf.comComposici%u00f3n de la microbiota intestinal en poblaciones pedi%u00e1tricas con obesidad: una revisi%u00f3n sistem%u00e1ticaMarti A., Canas I y Tamez H.An. R. Acad. Farm.Vol. 90. n%u00ba 1 (2024) %u00b7 pp. 125-135sessions /week in OB subjects compared to a controlgroup (normal weight) (30).The 3rd study ran for 6 weeks, combining physicalactivity (150 min/ week) and a dietary intervention(increasing fruit and vegetable consumption, replacingrefined carbohydrates with whole grains, and limitingthe consumption of sugar added to processed food andsugar-sweetened beverages) in OB subjects (31). The 4th study was an 8-week weight reductionprogram with 3 visits receiving counseling fromdietitians, personal trainers, research nurses, andpediatric clinicians, in which OB participants wereallocated in either a fat loss group or fat gain group,compared to normal- weight children (32). The results from the observational and interventionstudies (Table 2 and Table 3) will be discussed in termsof taxonomic classifications separated by phylum,order, family, genus, and species. In the results, we willdiscuss the most significant findings -those that hadsimilar outcomes at least in 2 independent studies-,which are presented in Table 4 and Table 5. 3.1. Observational Studies First, we will comment on the baseline resultscombining observational and intervention studiesregarding the phylum level analysis of gut microbiota.A higher abundance of Firmicutes inchildren/adolescents with OB compared to normalweight in six studies was found, from which 5 wereobservational (23,26%u201328,33) and one was anintervention study (31). Firmicutes levels in adultshave also been described to be increased (39) andrelated to increased consumption of food rich in animalfat in children (33). This bacterium is positivelycorrelated with serum tumor necrosis factor alpha(TNF-alfa) which is closely related to inflammatorylevels. (28). Notably, four studies; three observational (27,33,34),and one intervention study (32), reported a lowerabundance of Bacteroidetes in children/adolescentswith Ow/OB when compared to normal weight.Bacteroidetes increase energy absorption (27) and anegative relationship between their dominance andbody weight is found in adults with Ow/OB (33). Resultsin this review of low levels of Bacteroidetes and highlevels of Firmicutes are supported by previous adultstudies, which indicate a higher Firmicutes:Bacteroidetes ratio related to OB and inflammationlevels (34,40%u201342).Four studies; two observational (23,26) and twointervention studies (30,31) indicated a higherabundance of Proteobacteria in children/adolescentswith Ow/OB when compared to normal weight(23,30,31) and metabolically unhealthy obese (MUO)compared to metabolically healthy obese (MHO) (26).In adult studies low abundance of this phylum havebeen associated with a healthy intestinal microbiota(39). Recent studies have focused on the identificationof Proteobacteria, which might be implicated in thegenesis of endotoxemia and in the development ofmetabolic disorders (44). It can be concluded thatFigure 1. Flow diagram of the article selection process for this systematic review