Food for Thought: Chew on This Weight Loss Advice
Researchers from Iowa State University are presenting their findings at the Experimental Biology 2012 Conference in San Diego, California this month that demonstrates that the old weight loss tip of taking your time by chewing longer and slower during a meal can help a person eat less.
Previously, this weight loss tip was based on the idea that a hunger hormone called ghrelin would be suppressed while other hormones involved in feelings of fullness and satiety would be increased, and thereby signal the brain that the body had consumed enough food.
In fact, the ISU researchers’ results indicate that the basis of this weight loss tip is valid and can lead to less food consumed during a meal.
In the study, 20 ISU students were given a metronome and told to chew every time it ticked. The students were divided into two groups where the metronome ticked for 15 times with one group and 40 times with the other group before the two groups were allowed to swallow their chewed food. During the study, plasma glucose and hormone levels were measured as well as the students’ sense of appetite.
What the researchers found was that the students who chewed more actually ate less than the students who chewed less.
"When people chewed the pizza 40 times before swallowing, there was a reduction in hunger, preoccupation with food and a desire to eat," said James Hollis, an Iowa State assistant professor of food science and human nutrition who is co-authoring the study. "There was an increase in CCK, which is a hormone related to fullness and satiety. And there was a reduction in ghrelin, another hormone that stimulates the brain to increase appetite."
However, their results also showed that the blood glucose and insulin levels were higher in the group that chewed their food more times before swallowing. This means that absorption of fats and carbohydrates were increased with the increased chewing.
According to Hollis, "…increased mastication breaks down the food more thoroughly in the mouth, and this really facilitates nutrient absorption. That means you're getting more glucose and carbohydrates into the blood stream, which requires a larger insulin response to maintain plasma glucose levels."
What is not clear, however, is whether or not increased chewing will then offset the dieting value of eating less. In a previous study done with test subjects chewing nuts, Hollis found that more chewing led to less eating, but also an increase in the absorption of fat from the nuts.
"So while you get a reduced appetite, you also absorb more energy from the nuts. It's not clear which is more beneficial—the reduced appetite, or whether it's outweighed by the increased absorption of lipids and fat," he states.
With respect to appetite suppression, the researchers also noted that at least part of the desire to eat less may be from the test subjects’ reported dislike of chewing food so much and having to hold it in their mouths longer than they normally would. Such feelings of displeasure during eating could mask the true hunger and satiation hormone influences.
Therefore, while there appears to be truth in the weight loss advice to chew your food more slowly and thoroughly, there is also the chance that the increased calorie absorption could interfere with weight loss goals. Perhaps a new weight loss study/diet will come out that categorizes foods by the speed with which each should be eaten to balance both caloric intake and feelings of fullness.
Image Source: Courtesy of MorgueFile
Reference: Iowa State University News