The belief that breakfast is the most important meal of day has been derived from cross-sectional studies that have associated breakfast consumption with a lower BMI. This suggests that breakfast omission either leads to an increase in energy intake or a reduction in energy expenditure over the remainder of the day, resulting in a state of positive energy balance. However, observational studies do not imply causality. A number of intervention studies have been conducted, enabling more precise determination of breakfast manipulation on indices of energy balance. This review will examine the results from these studies in adults, attempting to identify causal links between breakfast and energy balance, as well as determining whether consumption of breakfast influences exercise performance. Despite the associations in the literature, intervention studies have generally found a reduction in total daily energy intake when breakfast is omitted from the daily meal pattern. Moreover, whilst consumption of breakfast supresses appetite during the morning, this effect appears to be transient as the first meal consumed after breakfast seems to offset appetite to a similar extent, independent of breakfast. Whether breakfast affects energy expenditure is less clear. Whilst breakfast does not seem to affect basal metabolism, breakfast omission may reduce free-living physical activity and endurance exercise performance throughout the day. In conclusion, the available research suggests breakfast omission may influence energy expenditure more strongly than energy intake. Longer term intervention studies are required to confirm this relationship, and determine the impact of these variables on weight management.
Breakfast skipping: Satiety: Gut hormonesOverweight and obesity are defined as a BMI of 25-29·9 and >30 kg/m 2 , respectively, and are positively associated with several chronic diseases, representing a substantial health and economic burden on society (1,2) . Obesity is a growing concern with the worldwide prevalence of obesity more than doubling between 1980 and 2008 (3) . It has also been shown that BMI increases continuously throughout adulthood (4) suggesting that longterm behavioural changes are required to curtail this pattern of weight gain. This necessitates the study of both lean and overweight populations, to ensure that dietary interventions are applicable for both reducing BMI in overweight and obese populations, and preventing the increase of BMI in lean populations.Breakfast can be defined as the first meal of the day, consumed within 2 h of waking, before commencing daily activities, and has been suggested to contain 20-35 % of daily estimated energy requirements (5) . Breakfast has long been considered an integral part of a healthy balanced diet (6) . This is partly due to associations in the literature that show individuals who regularly omit breakfast have a higher BMI (7,8) and increased prevalence of obesity-related chronic diseases (5) , including type-2 diabetes (9) and CHD (10) . Despite this, brea...