Fish oil-supplementation increases appetite in healthy adults. A randomized controlled cross-over trial

• The first cross-over trial on effects on appetite sensation in healthy men and women.
• Post-prandial sensation of being full was 20% lower after 3 weeks fish oil vs. soy oil.
• In women, fish oil also induced a 1.5× increased desire to eat more after a test meal.
• This new fish oil effect may give clues to its CNS-modulating mechanism.
• If verified, fish oil may be used to stimulate appetite e.g. in cancer cachexia.

Marine n-3 fatty acids are hypothesized to have beneficial effects on obesity and cancer cachexia possibly via an effect on appetite. The aim of this study was to investigate, if fish oil-supplementation affects appetite in healthy individuals. In a randomized cross-over study, 20 normal-weight subjects (50% females) were given ten 0.5-mL capsules/day of fish oil or soybean oil for 3 weeks separated by 1-week wash-out. In the end of each period, appetite was assessed by 10-cm visual analog scales immediately before and after a standardized breakfast. Results were analyzed in accordance with the paired design considering oil sequence and gender. All subjects completed both periods with a compliance of 96% and oil sequence did not affect the results. There was no difference between the two supplements in any pre-breakfast appetite scores, but the post-prandial sensation of being full was 1.21 cm (0.20; 2.22) lower after the fish oil-period. Furthermore, there was a supplement × gender-interaction on “desire to eat more” due to a score increase of 1.09 cm (0.28; 1.90) in women only. These results suggest that marine n-3 fatty acid may increase appetite. This finding would be potentially beneficial for patients with compromised nutritional status.