To investigate how dietary patterns (DP) change following engagement in a weight management programme. Using the DP identified, to study their relationship with weight loss achieved and ability to meet the Scientific Advisory Committee on Nutrition’s 2015 fibre and sugar recommendations.

Secondary analysis of FFQ data, which collected dietary information at two time points: retrospectively before (T0) and presently during (T1) Slimming World’s programme, was analysed. Principal component analysis derived the DP present.

Online FFQ, hosted by Slimming World (SW) in the UK.

Female SW members (n 325; 17–68 years old).

At T0, two DP, ‘plant based’ and ‘processed meat and sugar added by the consumer’ were identified. At T1, three DP were identified, ‘high meat’, ‘high fat salt and sugar (HFSS) products’ and ‘nuts and oils’. Participants with a diet low in ‘HFSS products’ lost significantly more weight (P for trend = 0·001), were more likely to consume breakfast (P = 0·021) and consumed less free sugar compared with high ‘HFSS product’ consumers. Those initially presenting with a low ‘plant based’ diet score lost more weight at T1 (P for trend = 0·046). With engagement, mean fibre intake increased from 24·3 to 32·4 g/d (P < 0·001) and free sugar intake decreased from 12·6 to 8·7 % total dietary energy (P < 0·001).

An individual’s DP before and with engagement in a weight management programme may indicate their weight loss success. Advising reduced HFSS product intake may aid initial weight loss. SW appears to promote dietary changes towards UK fibre and sugar recommendations.