A large body of research suggests that the micronutrient composition of meal is important in determining the satiety of the individual. In particular, high protein intakes appear to cause greater satiety than high carbohydrate or high fat meals. Protein is able to create satiety because it causes the release of peptide anorexic hormones that act on the hypothalamus to switch off the hunger signals. It is known that there is a circadian pattern of hormone release in animals, and so it is possible that the satiety induced by protein follows a diurnal pattern. For example, research suggests that meal size increases throughout the day and that the interval between meals decreases through out the day, such that 150 % more food is ingested in the evening relative to the morning. This pattern has also been recorded in laboratory animals.
To investigate the feeding patterns of humans and how they are affected by the time of day, researchers1 collected 7 day food diaries from 375 men and 492 women and analysed the food intakes between 0600 and 0959, 1000 and 1359, 1400 and 1759, 1800 and 2159, and 2200 and 0159. The results showed that the amount of food ingested in the morning was negatively correlated with the total amount of food ingested over the course of the day. In contrast, the amount of food ingested in the evening was positively correlated with the amount of food ingested over the course of the day. The researchers also measured the energy density of the foods and found that the energy density of the foods was positively correlated with the total intake of food over the course of the day.
These results provide evidence that meal timing is important in determining the total amount of food eaten in a day. Eating food earlier in the day appears to reduce appetite later in the day. This effect was seen during both weekdays and weekends and was evident in both men and women. This would tend to suggest that eating larger meals earlier in the day would promote weight loss perhaps if accompanied by a high protein diet. These findings also support previous work that suggests that when high density food is consumed, more calories are consumed that when lower density food is consumed. The results from this study therefore suggest that eating increased quantities of lower energy food during the early part of the day can reduce the amount eaten later in the day in such a way that total energy consumed is reduced.
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