Chewing uses a surprising amount of energy. An experiment that looked at the energy use associated with chewing gum found that it can increase bodily energy use by up to 15 percent.
Adam van Casteren at the University of Manchester in the UK and his colleagues measured energy use in 21 people between 18 and 45 years old as they chewed gum for 15 minutes. Each participant was asked to chew two types of gum—one soft and the other tough—so they could compare the effects of the gum's properties on the participants' energy use. Energy use was measured using a specially made cap covering the participants' heads. "You can use the cap to work out how much energy is being used," says Casteren. Before the experiment, the participants had all worn the cap while they sat watching a film in order for the researchers to know their base level energy use.
The researchers found that chewing the soft gum increased energy expenditure by about 10 percent, while chewing the tougher gum increased this use by around 15 percent. Casteren says it's interesting that a small change in the properties of the gum had such a clear effect on energy use.
The findings suggest that the energy use required to chew also explain why we developed such strong teeth for the action. Any amount of energy lost while chewing food, makes the meal a less efficient source of energy, so we must finish the action as soon as possible.
Dylan Thompson at the University of Bath in the UK says the increase is still only a small amount overall. "It will contribute less than 1 percent of total daily energy use because of relatively short daily chewing time," he says.
