Social facilitation of energy intake in adult women is sustained over three days in a crossover laboratory experiment and is not compensated for under free-living conditions.

People eat more when they eat a meal with familiar others than they do when eating alone. However, it is unknown whether eating socially impacts intake over the longer-term. The aim of Study 1 was to examine whether socially facilitated intake is sustained across all meals and across three consecutive days. The aim of Study 2 was to examine whether increased intake during a social meal taken in the laboratory is compensated for under free-living conditions. In Study 1, adult women (n = 26) ate all their meals across three days either with a friend or alone in a counterbalanced cross-over design. In Study 2 adult women (n = 63) consumed a meal in the laboratory either alone or with two friends and then recorded everything they ate and drank for the next three days using electronic food diary software. In Study 1 intake across 3 days was significantly greater in the Social (M = 7310 kcal, SD = 1114) than in the Alone condition (M = 6770 kcal, SD = 974) (F(1,423) = 16.10, p < .001, d = 0.51). In Study 2 participants consumed significantly more in the laboratory when eating with their friends (M = 1209 kcal, SD = 340) than when eating alone (M = 962 kcal, SD = 301) (F(1,63) = 13.28, p = .001, d = 0.77). Analysis of food diary data plus laboratory intake showed that intake remained significantly greater in the Social (M = 6396 kcal, SD = 1470) than in the Alone condition after 4 days (M = 5776 kcal, SD = 1182) (F(1,59) = 5.59, p = .021, d = 0.05). These results show that social facilitation of eating is sustained over three days and suggest that people fail to compensate for the social facilitation of eating.