Despite evidence that formula very low-energy diets (VLED) and low-energy diets (LED) are both effective and safe as treatments for obesity and type 2 diabetes, these diets remain underutilized in the United Kingdom. The aim of this study was to explore UK dietitians' attitudes and experiences of using formula VLED and LED. A cross-sectional survey was disseminated between September 2019 and April 2020 through websites, social media platforms and dietetic networks using snowball sampling. In total, 241 dietitians responded to the online survey with 152 participants included in the final analysis (female [94.1%], mean age 40.8 years [SD 9.5]; median 12 years [interquartile range 8, 22] within dietetic practice). One hundred and nine (71.7%) participants reported currently using VLED/LED in clinical practice and 43 (28.3%) did not. Those with lower motivation and confidence in implementing VLED/LED in clinical practice were less likely to use them.Cost and adherence were the two highest reported barriers to use. Dietitians perceived VLED/LED were effective, but concerns remained about long-term effectiveness, particularly for some patient groups. Dietitians also reported that further education, funding and service infrastructure, including access to clinic space and administrative support, were required to help embed VLED/LED into routine clinical practice. With clinical services now regularly offering VLED/LED programmes in the United Kingdom, dietitians are ideally placed to provide long-term support. However, understanding, reporting and addressing the potential barriers (funding/infrastructure and education) appear to be key requirements in increasing the delivery of VLED/LED programmes nationally.