Background/objectives: We have previously shown that 500 ml of a foamed drink ('foam') significantly improved appetite versus a non-foamed control. The objectives of this research were to assess the effect of smaller volumes of foams on appetite, and the potential benefits of foam ingestion and its timing on appetite measures in a reduced-energy context.
Subjects/methods: Two randomized, parallel design studies (pre- and main study) were conducted using healthy adult subjects. Pre-study: 133 subjects (age 18-50 years, body mass index (BMI) 20-32 kg m(-2)) each consumed either 10, 25, 50, 100, 150 or 250 ml foamed meal replacer (~0.2 kcal ml(-1)), 150 min after a fixed breakfast. Main study: four groups of subjects (n=134; age 18-60 years, BMI 22.5-35.0 kg m(-2)) consumed 200 ml/22 kcal foam (based on pre-study results) immediately after main meals (M), after snacks (S), in-between snacks and main meals (I) or not at all (control, C) within 1 day of a reduced-energy meal plan consisting of three main meals and three snacks. Measurements included self-reported appetite (six scales, reported as area under the curve (AUC)) and (main study only) end-of-day appetite questionnaire.
Results: Pre-study: the strongest effect on appetite was produced by 250 ml (consistent across scales), whereas 150 ml showed more pronounced effects than 100 and 50 ml in most scales. Volumes 10 and 25 ml had no effects on any scale. Main study: 200 ml foam reduced appetite AUC substantially in all treatments, particularly M (for example, hunger AUC reduced by 35% (P <0.001), 28% (P <0.05) and 20% (P=0.11) for M, S and I, respectively versus C). A strong reduction in 'appetite for a snack' was seen for all timings (all P <0.05). The end-of-day appetite ratings confirmed these findings.
Conclusions: Modest amounts of a low-energy foam can reduce appetite measures during a 1-day reduced-energy meal plan.