Background: Probiotic bacteria have been shown to have various effects on the microbiota; this may also affect appetite and may help promote weight loss and maintenance. Objective: This study was conducted to investigate the effect of Lactobacillus paracasei subsp paracasei L. casei W8 (L. casei W8) on glucagon-like peptide-1 (GLP-1) responses in an isolated pig intestine, in piglets and postprandially in humans. Additionally, the effect on subjective appetite, ad libitum energy intake, and glucose and insulin responses in humans was investigated. Design: Piglets were fed with probiotics for 2 weeks and the effect on glucagon encoding gene (GCG) was investigated. An isolated pig intestine was perfused with L. casei W8 and the GLP-1 response was measured. Twenty-one subjects completed a randomized, controlled, crossover study with three arms. Each participant completed 3 test days testing the effect of low dose (LD) (10(9) CFU), high dose (HD) (10(10) CFU) L. casei W8 or placebo capsule. Subjective appetite was assessed before an ad libitum lunch was served. GLP-1, insulin and glucose concentrations were analyzed. Results: Two weeks of treatment of piglets with L. casei W8 resulted in an increase in GCG expression compared to control animals (P <0.05). L. casei W8 increased the GLP-1 response in the isolated pig intestine. In humans, L. casei W8 had an overall effect on energy intake (P = 0.03), but no effects on subjective appetite sensation, overall glucose and insulin response and on GLP-1 release were observed (P > 0.1). Conclusion: The probiotic bacteria L. casei W8 appears to lower food intake acutely, but the underlying mechanisms are not understood.