Mechanism
After drinking some water, how much you want to eat hydrating foods like an apple or orange will decrease relative to how much you want to eat something like an apple pie or some chips [1, 2]. This is because dehydration decreases the appeal of foods with higher salt content, and increases the appeal of foods with higher water content [2]. This is important since foods with a higher water content tend to have a higher micronutrient density and lower caloric density, while salty foods tend to be highly processed and calorie dense [2].
Caloric Intake
In multiple papers where dehydrated and normally hydrated subjects were compared, the dehydrated subjects consumed significantly fewer calories than the euhydrated ones [3 - 5]. This effect is dependent on the food available. When cereal bars were provided, dehydrated subjects consumed 760 fewer calories [5], whereas when a wet porridge was provided, there was little effect [6]. Interestingly, drinking a lot of water shortly before a meal can increase satiety through gastric distention, so both reducing and increasing water intake can potentially make weight loss easier (depending on the situation) [1, 6].
After drinking some water, how much you want to eat hydrating foods like an apple or orange will decrease relative to how much you want to eat something like an apple pie or some chips [1, 2]. This is because dehydration decreases the appeal of foods with higher salt content, and increases the appeal of foods with higher water content [2]. This is important since foods with a higher water content tend to have a higher micronutrient density and lower caloric density, while salty foods tend to be highly processed and calorie dense [2].
Caloric Intake
In multiple papers where dehydrated and normally hydrated subjects were compared, the dehydrated subjects consumed significantly fewer calories than the euhydrated ones [3 - 5]. This effect is dependent on the food available. When cereal bars were provided, dehydrated subjects consumed 760 fewer calories [5], whereas when a wet porridge was provided, there was little effect [6]. Interestingly, drinking a lot of water shortly before a meal can increase satiety through gastric distention, so both reducing and increasing water intake can potentially make weight loss easier (depending on the situation) [1, 6].
- Rogers, P. J., Ferriday, D., Irani, B., Hoi, J. K. H., England, C. Y., Bajwa, K. K., & Gough, T. (2020). Sweet satiation: Acute effects of consumption of sweet drinks on appetite for and intake of sweet and non-sweet foods. Appetite, 149, 104631.
- Carroll, H. A., Templeman, I., Chen, Y. C., Edinburgh, R., Burch, E. K., Jewitt, J. T., ... & Betts, J. A. (2019). Hydration status affects thirst and salt preference but not energy intake or postprandial ghrelin in healthy adults: A randomised crossover trial. Physiology & behavior, 212, 112725.
- Pérez-Luco, C., Díaz-Castro, F., Jorquera, C., Troncoso, R., Zbinden-Foncea, H., Johannsen, N. M., & Castro-Sepulveda, M. (2019). Fluid restriction decreases solid food consumption post-exercise. Nutrients, 11(6), 1209.
- Engell, D. (1988). Interdependency of food and water intake in humans. Appetite, 10(2), 133-141.
- Shirreffs, S. M., Merson, S. J., Fraser, S. M., & Archer, D. T. (2004). The effects of fluid restriction on hydration status and subjective feelings in man. British Journal of Nutrition, 91(6), 951-958.
- Corney, R. A., Horina, A., Sunderland, C., & James, L. J. (2015). Effect of hydration status and fluid availability on ad-libitum energy intake of a semi-solid breakfast. Appetite, 91, 399-404.
