The investigation consisted of a laboratory study with 10 healthy subjects who were both sleep and food deprived prior to each experimental condition. The aim of the study was to investigate the importance of energy content and the bulk of food on wakefulness and satiation. Each subject was tested in four conditions, each with equal food composition but different energy amounts: 100, 500 and 1000 kcal and 100 kcal with low bulk content. Recordings and ratings of wakefulness and satiations were carried out throughout the investigation, starting 30 minutes before and continuing until 90 minutes after intake of the food alternatives. No differences in wakefulness could be observed after the four food alternatives. However, subjects rated themselves as more satiated after the food alternatives with higher energy content and higher bulk.