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87 Functional defecation disorders and overweight 3 studies conducted in developed countries (Germany, the Netherlands, and the United States) seem to demonstrate an association between FDDs and excessive bodyweight, whereas studies in developing countries (Brazil, Colombia, and Iran) were unable to confirm this finding. This raises the question whether there are pathophysiological differences between developing countries and more economically developed countries regarding the association between FDDs and excessive body weight. Possible shared etiological factors involved in the pathogenesis of overweight/obesity and FDDs are eating behavior, low fiber intake, physical exercise, hormonal dysfunction, gut microbiota, genetic predisposition, psychological factors, and socioeconomic status. 1,9,13,16,21 Many of these factors likely differ between developed and developing countries. Potentially, a high-calorie, high-fat, low- fiber diet and a sedentary lifestyle, which are common in developed countries, impact body weight and FDDs differently compared with lifestyle habits in developing countries. One other potential pathophysiological factor that has been under increased attention over the past decades is the gut microbiota. It has been well established that obesity is associated with changes in the composition of the gut microbiota. 55–62 Studies in mice and humans strongly suggest that the gut microbiota plays an important role in energy metabolism and that there is a causative role for the microbiota in the development of obesity. 55,56,61 Gut microbiota involvement in children with constipation has also been suggested. 63 Although it is yet unclear whether the gut microbiota plays a causative role, it has been suggested that biochemical substances related to the gut microbiota may influence motility. 8,63–66 It is highly likely that dietary factors also play an important role in these microbiota-associated biochemical processes. 67–69 However, further studies in this field are needed to further elucidate the association between the gut microbiota, FDDs, and excessive body weight. Several studies specifically revealed that fecal incontinence (FNRFI, FC-associated fecal incontinence, and fecal incontinence not otherwise specified) was more common in children with excessive body weight. 13,28–30 However, not all included studies reported on fecal incontinence; therefore, it is difficult to draw firm conclusions from these pediatric data. A high prevalence of fecal incontinence has been previously described in obese adults, and in the adult population fecal incontinence may improve after weight loss due to bariatric surgery. 70,71 The underlying pathophysiological mechanism behind this association is incompletely understood, but it has been hypothesized that this is due to pelvic floor dysfunction. 72,73 Most likely, the excessive weight on the pelvic floor causes direct mechanical and neurologic dysfunction together with indirect effects of obesity such as diabetes, nerve conduction abnormalities, and intervertebral disc herniation. 71,72 Whether the same mechanisms apply in children is yet to be sought out. These findings warrant further studies, especially because fecal incontinence is known to have a major negative impact on quality of life. 5,6