The purpose of this study was to examine the effects of a very low-energy, viscous placebo breakfast meal on subjective appetite sensations during the morning, and food intake at lunch, compared to a typical whole-food breakfast meal and a water-only control. Participants will not be told that the placebo breakfast contains nearly no energy until the end of the study. The breakfasts will be provided in a randomised order, with a period of at least four days separating the trials. Blood samples will be taken before and after the breakfast is eaten to see how appetite-regulating proteins and blood sugars respond during the morning. Appetite questionnaires will also be completed throughout the morning, and a pasta-based lunch meal will be provided so that voluntary food intake can be measured.

Obesity is a risk factor for several chronic diseases, including type-2 diabetes, heart disease and some forms of cancer. There is clear evidence demonstrating that weight gain occurs progressively over the lifespan, highlighting that preventative action should be taken by young, lean individuals, who may yet develop overweight or obesity later in life. A positive energy imbalance, in which energy intake exceeds energy expenditure for a sustained duration, is known to be the underlying systematic cause of obesity. Therefore, reducing daily energy intake is a seemingly simple solution to the this problem. However, compensatory alterations in appetite regulation which stimulate an increase in energy intake often impede the long-term success of such interventions.

Extending the overnight fasting period, thereby restricting the time available for food intake, has emerged as an effective dietary strategy for reducing daily energy intake and may assist with weight management. Laboratory studies have shown that skipping breakfast typically results in increased appetite during the morning, and an increase in energy intake at lunch. Therefore, the long-term success of skipping breakfast may be reduced by elevated appetite sensations. A recent study which aimed to assess the effects of a very-low energy, placebo breakfast on resistance exercise performance noted that appetite was suppressed after consuming the placebo, despite its lack of energy content. Whether this suppression of appetite following placebo breakfast consumption results in a reduced energy intake at lunch, is currently unknown. Therefore, the investigators are interested to examine the subjective and hormonal appetite responses to placebo breakfast consumption, compared with these responses to an overt breakfast consumption trial an overt breakfast skipping trial, and whether these changes result in any differences in voluntary energy intake at lunch.

The present study is a randomised, controlled, crossover study in which fourteen healthy, habitual breakfast-consuming (self-reported) males will consume a very low-energy, viscous placebo breakfast, a typically consumed, whole-food breakfast, and a water-only control. At least four days will separate trials.

Participants will firstly complete a pre-screening session in which anthropometric data will be collected. This will be used to determine the energy content of the typical whole-food breakfast.

Inclusion Criteria:

• Non-smoker.
• Habitually consuming breakfast at least 3 days per week.
• Have maintained a stable weight for 6 months (self-reported).
• No known history of gastric, digestive, cardiovascular or renal disease.

Exclusion Criteria:

• Food allergies, dislike or intolerance of study foods or drinks.
• Not currently on a weight management program or have irregular eating patterns (i.e. extended fasting periods >8h other than overnight - self reported).
• Use of medication that may affect hormone concentrations.
• Excessive alcohol consumption (>4 units/day).
• Intensive training schedule (>10 hours/week).

Due to the obvious differences between the three breakfasts meals (viscous, jelly-like placebo breakfast, typical whole-food breakfast, water-only control), participants will be aware that the three trials are different. However, they will not be told that the placebo breakfast contains nearly no energy, and therefore, are blinded to this aspect of the study.