BackgroundAdults with intellectual and developmental disabilities (IDDs) experience eating, drinking and swallowing problems, such as chewing problems, choking, gagging, coughing during eating, aspiration and rumination syndrome, which may lead to poor nutritional status. This study aimed to determine the relationship between IDD levels, eating, drinking and swallowing problems and nutritional status in adults with IDDs.MethodsThe sample consisted of 71 participants (37 men and 34 women) with a mean age of 22.5 ± 7 years (range 18–60 years). Professionals classified intellectual disability as mild, moderate or severe. The Screening Tool of Feeding Problems scale was applied to the caregivers of adults with IDDs to identify eating, drinking and swallowing problems. Dietary intake was assessed using a 24‐h dietary recall and a food and nutrition photograph catalogue. The researchers measured body weight, height and middle upper arm circumference. Body mass index was calculated. Four body mass index categories were determined: underweight (<18.5 kg/m2), normal weight (18.5–24.9 kg/m2), overweight (25.0–29.9 kg/m2) and obese (≥30 kg/m2). Chi‐squared tests were used to detect the relationship between IDD levels and eating and drinking problems, and analysis of variance tests were conducted to detect the relationship between IDD levels with anthropometric measurements and dietary intake.ResultsParticipants had mild (42.3%; n = 30), moderate (29.6%; n = 21) or severe IDD (28.2%; n = 20). They were underweight (12.7%; n = 9), normal weight (59.2%; n = 42) or overweight and/or obese (28.2%; n = 20). Participants with severe IDD had significantly higher Screening Tool of Feeding Problems ‘nutrition‐related behaviour’ and ‘eating and drinking skill deficit problem’ sub‐scale scores than those with mild IDD. However, the groups had no significant difference in ‘food refusal and selectivity’ sub‐scale scores. Participants with severe IDD also had anorexia prevalence similar to those with mild IDD. The groups did not significantly differ in anthropometric measurements, daily energy intake and macronutrient and micronutrient intake.ConclusionsWhile adults with severe IDD had more eating and drinking skill deficits (e.g. chewing problems and independent eating difficulties) and nutrition‐related behaviour problems than those with mild IDD, the eating, drinking and swallowing problems, which may critically affect their food intake, were similar to adults with mild IDD. The anthropometric measurements and energy and nutrient intakes of adults with severe IDD were not significantly different from those with mild IDD consistently. Findings indicate that nutritional deficiencies and nutritional behaviour problems may be avoidable in adults with IDDs.