Reports suggest that decreasing numbers of people are consuming breakfast regularly, and yet at the same time evidence suggests that breakfast may be protective of obesity. For example, epidemiological studies have reported that regular consumption of breakfast is associated with a lower body mass index, and those who successfully maintain weight loss are more likely to be frequent breakfast consumers. While the cause and effect is not clear, there is the possibility that breakfast consumption could affect subsequent energy intake through hormonal, metabolic and physiological changes. In particular, some evidence suggests that appetite may be reduced in frequent breakfast eaters, although there is little data available on the subsequent effects on physiological changes. Researchers have therefore been interested in assessing the feeding habits and physiological changes in those who regularly consume breakfast.
For example, research1 published in the Journal of Nutrition investigated the effects of breakfast consumption on energy intake and feeding behaviour in 12 normal-weight healthy male volunteers (mean age 23 years). In a random crossover design, subjects consumed breakfast (10% of daily energy, 15% protein, 14% fat, 72% carbohydrate), and were then provided with a 400mL 251kcal liquid meal 150min later. Lunch consisted of an ad libitum mixed meal. Subjects then repeated the protocol, but missed breakfast. Abstinence of breakfast cause a significant increase in plasma free fatty acid (FFA), suggesting that energy utilisation had switched to the oxidation of fat. Following the liquid meal, FFA remained elevated compared to the breakfast group, and the area under the curve for insulin and glucose were higher in the no breakfast group, which is consistent with previous reports of glucose and insulin responses following fasting.
In the breakfast group, subsequent ingestion of the liquid meal caused a greater increase in glucagon-like peptide-1 (GLP-1) and plasma peptide YY, when compared to the no breakfast group. Both GLP-1 and peptide YY are known appetite suppressants, which may explain why the subjects in the breakfast group reported increased satiety and a reduced desire to eat. There was also a significant reduction in the peak values of plasma ghrelin in the breakfast group, further suggesting that appetite had been reduced. In addition, the energy consumption at the lunchtime meal was 17% lower that the no breakfast group, suggesting that missing breakfast caused the participants to compensate by increasing energy at a subsequent meal when calories were not restricted. Taken as a whole these results support the contention that breakfast can have beneficial effects on body weight due to better regulation of appetite and blood glucose.
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