This study assesses the effect of the low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet on gastrointestinal (GI) and behavioral problems in children with autism spectrum disorder (ASD). The objectives of this study are: -To determine whether the low FODMAP diet causes a decrease in gastrointestinal problems related to ASD -To determine whether the low FODMAP diet causes a decrease in behavioral problems -To assess the effect of decreased gastrointestinal problems on reduction of behavioral problems

In this study, participants were children with autism spectrum disorder (ASD) ages 6-17 years. Children with ASD were randomized to the low FODMAP diet or habitual diet for 2 weeks. At baseline and after a two-week intervention period, the parent/caregiver completed the Aberrant Behavior Checklist-Community and Pediatric Quality of Life Inventory Gastrointestinal Module. The parent/caregiver also completed a dietary food record, and stool consistency/frequency record (three days before start to intervention and the last three days of the intervention) of their children.

Inclusion Criteria:

• 6-17 age range
• Diagnosed with autism spectrum disorder
• Parent/Caregiver report of constipation and /or abdominal pain. • ROME IV criteria was utilized to identify constipation (defined as the presence of two of more of the following symptoms: Two or fewer stools per week, at least 1 episode of fecal incontinence per week, history of retentive posturing or excessive volitional stool retention, history of painful or hard bowel movements, presence of a large fecal mass in the rectum, history of large diameter stools that can obstruct the toilet) • ROME IV criteria was utilized to identify abdominal pain (defined as the fulfilled at least 4 times per month and include all of the following: episodic or continuous abdominal pain that does not occur solely during physiologic events (eg, eating, menses), insufficient criteria for irritable bowel syndrome, functional dyspepsia, or abdominal migraine, the abdominal pain cannot be fully explained by another medical condition)

Exclusion Criteria:

• Under 6 and over 17 years old
• Having a specific restrictive diet to treat allergies or a specific chronic disease - Any history of abdominal surgeries
• Any history of chronic physiological GI disorders such as celiac, inflammatory bowel disease, eosinophilic esophagitis.
• Any chronic condition that may impact GI function such as thyroid disease, cystic fibrosis, or cardiac abnormalities