Study: Eating Slowly Might Not Help Obese Lose Weight

Researchers found eating meals slowly doesn't always reduce calorie intake.

Eating slowly doesn't help everyone reduce calorie intake, a new study found.
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Eating meals more slowly might make you feel less hungry, but that doesn't necessarily mean you'll consume fewer calories, as scientists previously speculated.

In a study published Monday in the Journal of the Academy of Nutrition and Dietetics, researchers from Texas Christian University examined how eating speeds affected calorie consumption in 35 normal-weight and 35 overweight or obese subjects, as defined by their body mass index scores.

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Although all the subjects ate the same meal of vegetable pasta in two conditions – one at a leisurely pace and one at a fast pace – only the normal-weight individuals saw a statistically significant reduction in calorie consumption during the slow meal. Individuals in the normal-weight group saw an 88 kcal reduction between the fast and slow meals, while overweight and obese individuals saw a 58 kcal reduction.

"A lack of statistical significance in the overweight and obese group may be partly due to the fact that they consumed less food during both eating conditions compared to the normal-weight subjects," said lead author Meena Shah, in a statement. "It is possible that the overweight and obese subjects felt more self-conscious, and thus ate less during the study."

The number of obese adults in the United States jumped from 14.5 percent in the early 1970s to 35.7 percent in 2009-10, according to the Centers for Disease Control and Prevention.

Scientists have speculated that the rapid rise in the prevalence of obesity among American adults can be at least partly attributed to a similar increase in the reported energy intake – the number of calories consumed in a day. One way to reduce energy intake, previous research suggested, is to reduce the speed of eating.

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A high eating speed, the study says, "impairs the congruent relationship between the sensory signals and the metabolic processes that determine how much we eat." Because the brain doesn't immediately register a feeling of fullness (research has shown it takes about 15 to 20 minutes) scientists have said eating more slowly could help reduce overeating.

Although previous studies found eating speed is positively related to body weight, they focused on normal or "mostly normal" weight individuals largely from one racial or ethnic group, the TCU study says. Additionally, the information on eating speed was self-reported, making it difficult to generalize any findings to the American population. Participants in the TCU study were given specific instructions about how to control their eating speeds.

But the reduction in calorie intake in the TCU study could have also been influenced by the fact that both groups consumed more water during the slow meal, the researchers said. Overall, participants in both groups consumed 9 ounces of water during the fast meal, compared with 12 ounces during the slow meal.

The normal-weight subjects increased their water intake during the slow meal by 27 percent, while the overweight and obese subjects drank 33 percent more water during the slow meal, compared with the fast meal.

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Despite the differences in calorie consumption between the two meals, both groups said they felt less hungry after the slow meal than after the fast meal.

Although eating speeds do not appear to have the same effect for all weight groups, further examining the relationship could be useful in developing strategies to help people of different weights reduce their calorie intake, Shah said. But the team said further research is necessary because it's still unclear if any reduction in hunger from eating more slowly would affect how people eat subsequent meals, or if it could lead to weight loss.

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