Background and Objectives. Obesity is a rapidly growing medical issue worldwide, and is fast becoming one of the leading causes of mortality. Data from our laboratory have demonstrated that alginates have the ability to inhibit pancreatic lipase activity in-vitro, and may therefore reduce the fat absorbed in the diet [1-3]. This project has developed a bread vehicle designed by Greggs PLC that incorporates alginate and may be used in foods that people are already consuming in a “health by stealth” manner in the battle against obesity. In an acceptability study with 40 participants there were no adverse side effects with either bread, and participants preferred the alginate bread compared to the control bread. The purpose of the present study was to assess the ability of alginate enriched bread to inhibit fat digestion in-vitro and in-vivo. Method. Control bread (CB) and alginate enriched bread (AB) were used in the current study. In-vivo: data presented is preliminary data from a double blind crossover study conducted using ileostomy patients (n=13). Participants consumed a calorific set meal the night before and were then fasted for 12h. Upon arrival participants consumed either 105g CB or AB as toast which included 20g of butter. Blood samples were taken at baseline, immediately post eating and then every 30 minutes for 5 hours, and placed on ice until analysis. Free glycerol and total triglycerides was measured in plasma to assess fat digestion. In-vitro: three fat substrates (Trioctanoate, Trioleate and Tributyrate) were digested in an open model gut system developed within this laboratory, which replicates digestion in the mouth, stomach and small intestines. 500µl of each substrate was added alone or with 5.2g AB or CB (n=9) at 0 minutes. A 1ml sample was then taken at 180 minutes for each sample. Free glycerol was measured to assess fat digestion. A t-test was used to compare CB and AB with normal substrate digestion in the model gut, and to compare total triglycerides in plasma between CB and AB at various time points in ileostomy patients. Data presented as mean ± standard error of the mean (SEM). Results. Preliminary data from ileostomy plasma samples indicated a reduction in the total triglycerides in the plasma ranging from 9-34% from 0-5h compared with the control bread, with a significant difference at 210 minutes (p>.05). In the model gut at 180 minutes there was a significant reduction in fat digestion of 47.7% (1.2), 32.5% (2.4) and 51.1% (1.3) for trioctanoate (p>.05), tributyrate (p>.05) and trioleate (p>.05) respectively. Conclusion. This study has the potential to provide evidence that normal foods supplemented with alginate can be used to treat obesity/overweight and could be utilised by the food industry. Further recruitment is required to acquire a larger group of ileostomy patients and to analyse the ileum effluent fluid to determine levels of undigested fat.