Emma J. Bertenshaw

Satiating effects of protein but not carbohydrate consumed in a between-meal beverage context.

Previous research has suggested that protein is the most satiating macronutrient; however some experiments have found no difference in satiating efficiency of protein and carbohydrate during short intervals after consumption. There is also evidence that the satiating effects of carbohydrate are minimal when in a beverage rather than solid context. To evaluate whether protein-based satiety was evident in a drink context, and clarify further effects of preload time on satiety, the present study compared iso-energetic dairy fruit drink preloads ( approximately 1250 kJ), differing in macronutrient composition and consumed at two time intervals in the morning. Using a counterbalanced within-subjects design, 18 unrestrained lean male volunteers consumed 300 ml of carbohydrate-enriched (CHO), protein-enriched and low-energy control (327 kJ) dairy fruit drinks, 120 min and 30 min before an ad libitum lunch. Significantly less energy was consumed at lunch after the protein (3234 kJ) compared to the control (3468 kJ, p<0.05) and CHO preloads (3588 kJ, p<0.05). However, this was not sufficient to show complete energy compensation. Preload time of consumption did not impact upon any measures. Only satiety ratings at the beginning of lunch varied significantly by preload type, reflecting differences in test meal intake. These findings are consistent with previous research that protein is more satiating than carbohydrate. The roles of sensory and hedonic characteristics are discussed.

Dose-dependent effects of beverage protein content upon short-term intake.

Protein is considered to be more satiating than carbohydrate, quantified by energy adjustment and subjective appetite. However, the effect of increasing protein content upon short-term energy adjustment in beverage contexts is unclear. This study used a repeated-measures, cross-over design. 28 male volunteers (18-35 years) ate a standard breakfast in the laboratory and 210 min later consumed one of four preloads 30 min prior to an ad libitum pasta meal. Three of the preloads were isocaloric ( approximately 1155 kJ) mixed composition dairy fruit drinks (300 g) of low (13% protein energy/87% carbohydrate energy), medium (25% protein energy/75% carbohydrate energy) and high (50% protein energy/50% carbohydrate energy) protein content. The control drink was a low energy (328 kJ) alternative. Results indicated a dose response effect of preload protein level on intake (g) at the ad libitum meal. Ad libitum intake was: control (637.6g+/-39.7), low (596.9 g+/-40.5), medium (546.9 g+/-34.7), and high protein (533.6g+/-42.3). 100% compensation was not achieved; however total energy intake after the medium and high protein drinks did not differ significantly from control. There were no significant differences in hunger and fullness ratings. Our findings support the view that increasing the protein composition of beverages relative to carbohydrate proportionally affects short-term subsequent intake in controlled conditions.

Perceived thickness and creaminess modulates the short-term satiating effects of high protein drinks

Previous research suggests that increasing beverage protein content enhances subsequent satiety, but whether this effect is entirely attributable to post-ingestive effects of protein or is partly caused by the distinct sensory characteristics imparted by the presence of protein remains unclear. To try and discriminate nutritive from sensory effects of added protein, we contrasted effects of three higher-energy (about 1·2 MJ) and one lower-energy (LE: 0·35 MJ) drink preloads on subsequent appetite and lunch intake. Two higher-energy drinks had 44% of energy from protein, one with the sensory characteristics of a juice drink (HP2, low-sensory protein) and the second a thicker and creamier (HPþ, high-sensory protein) drink. The high-carbohydrate preload (HCþ, high-sensory carbohydrate) was matched for thickness and creaminess to the HPþ drink. Participants (healthy male volunteers, n 26) consumed significantly less at lunch after the HPþ(566 g) and HCþ(572 g) than after HP2 (623 g) and LE (668 g) drinks, although the compensation for drink energy accounted for only 50% of extra energy at best. Appetite ratings indicated that participants felt significantly less hungry and more full immediately before lunch in HPþ and HCþ groups compared with LE, with HP2 being intermediate. The finding that protein generated stronger satiety in the context of a thicker creamier drink (HPþ but not HP2) and that an isoenergetic carbohydrate drink (HCþ), matched in thickness and creaminess to the HPþ drink, generated the same pattern of satiety as HPþ, both suggest an important role for these sensory cues in the development of protein-based satiety.

Acquired liking for sweet-paired odours is related to the disinhibition but not restraint factor from the Three Factor Eating Questionnaire

Previous research suggests that women scoring high on dietary restraint may be insensitive to flavour-flavour learning, but no study has yet explored this using the olfactory conditioning paradigm. Accordingly, 56 women who were sweet likers were classified as either high or low on both the Three Factor Eating Questionnaire restraint and disinhibition scales. They evaluated two odours before and after disguised pairings of one odour with 10% sucrose and the other with 0.01% quinine. Liking for the quinine-paired odour decreased post-training, with no effects of restraint or disinhibition. In contrast, the increase in liking for the sucrose-paired odour was significantly greater in women classified as scoring high in disinhibition, but was unaffected by restraint. Sweetness of the sucrose paired odour increased, and bitterness of the quinine-paired odour decreased, similarly in all groups. These data suggest that sensitivity of restrained eaters to flavour-based learning may result from their attitude to the food used as reinforcer rather than some basic failure in the learning process, and also suggest that women scoring high on disinhibition may show heightened sensitivity to hedonic cues.