Background and aims We have established that acute intraduodenal infusion of the fatty acid, lauric acid (“C12”), markedly reduces energy intake in healthy subjects in the absence of adverse effects. The aim of this study was to investigate the hypothesis that increasing doses of orally ingested C12 would result in a dose-related suppression of appetite and subsequent energy intake at breakfast and lunch. Methods 14 healthy men were studied on four separate occasions in double-blind, randomised fashion. Following ingestion of C12 (2 g (77 kJ), 4 g (153 kJ), or 6 g (230 kJ)) or control, energy intake at breakfast (30 min after C12 ingestion), perceptions of appetite, nausea and bloating (for 180 min following breakfast), and energy intake at lunch (180 min after breakfast), were measured. Results C12 ingestion did not induce nausea or bloating. While there was no effect of C12 on energy intake at breakfast, energy intake at lunch was reduced significantly after ingestion of both C12(2 g) (by 13.7%, P < 0.05) and C12(6 g) (by 18.1%, P < 0.01) compared with control, and tended to be less (by 8.7%, P = 0.1) following C12(4 g) (kJ; control: 4232 ± 151, C12(2 g): 3667 ± 283, C12(4 g): 3874 ± 315, C12(6 g): 3474 ± 237). Total energy intake (breakfast + lunch + C12 dose) was less following ingestion of C12(6 g) compared with control (by 7.8%, P < 0.05) (kJ; control: 8256 ± 297, C12(2 g): 7905 ± 269, C12(4 g): 8443 ± 421, C12(6 g): 7611 ± 384). Conclusion Acute administration of oral C12 reduces energy intake in lean humans. Clinical trial registration This study was performed in 2006/2007, i.e. prior to the requirement of clinical trial registration and, therefore, was not registered at the time.