Satiety, which is the inhibition of eating following the end of a meal, is influenced by a number of food characteristics, including compositional and structural factors. An increased understanding of these factors and the mechanisms whereby they exert their effects on satiety may offer a food-based approach to weight management. Water and gas, which are often neglected in nutrition, are major components of many foods and contribute to volume, and to sensory and other characteristics. A review of previous short-term studies that evaluated the effects of water or gas in foods on satiety showed that while satiety was generally increased, effects on subsequent intakes were not always apparent. These studies were diverse in terms of design, timings and food matrices, which precludes definitive conclusions. However, the results indicate that solids may be more effective at increasing satiety than liquids, but gas may be as effective as water. Although increased gastric distension may be the main mechanism underlying these effects, pre-ingestive and ingestive impacts on cognitive, anticipatory and sensory responses also appear to be involved. Furthermore, there is limited evidence that water on its own may be effective at increasing satiety and decreasing intakes when drunk before, but not with, a meal. Longer-term extrapolation suggests that increasing food volumes with water or gas may offer weight-management strategies. However, from a practical viewpoint, the effects of water and gas on satiety may be best exploited by using these non-nutrients to manipulate perceived portion sizes, without increasing energy contents.Food gas: Food water: Food volume: Energy intake: Portion size Obesity is a major public health issue, which occurs when energy intake exceeds energy expenditure, leading to a chronic positive energy balance. However, energy balance is under complex control, and over 100 interacting factors have been identified and described in a series of obesity system maps, which have energy balance at their core (1) . A key variable in energy balance is the degree of primary appetite control, which has physiological, psychological and behavioural determinants (1) . Drugs that suppress appetite and increase satiety offer one strategy to combat obesity (1) . However, compositional and structural variations between foods can lead to substantial differences in their effects on satiety (2) . An increased understanding of these compositional and structural factors and the mechanisms whereby they exert their effects on satiety may offer an alternative, food-based approach to weight management. Water and gas, which are the focus of this review, are major components of many foods, where they contribute to structure and texture, and also to sensory characteristics. However, as non-nutrients, water and gas are often neglected in nutrition. Following an overview of the assessment of satiety and the role of physiological and food factors in satiety, the water and gas contents of a range of foods are presented. Short-term studi...