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THURSDAY, Jan. 2, 2014 (HealthDay News) -- As people look for fresh strategies to cut back on calories and shed pounds, a new study suggests that simply eating more slowly can significantly reduce how much people eat in a single sitting.
The study involved a small group of both normal-weight and obese or overweight participants. All were given an opportunity to eat a meal under relaxed, slow-speed conditions, and then in a time-constrained, fast-speed environment.
The catch: Although all participants consumed less when eating slowly and all said they felt less hungry after eating a slow meal compared to a fast meal, only people who were considered normal weight actually reduced their calorie intake significantly when eating more slowly.
"One possible reason [for the calorie drop seen] may be that slower eating allows people to better sense their feelings of hunger and fullness," said study author Meena Shah, a professor in the department of kinesiology at Texas Christian University, in Fort Worth.
Slow eating also seemed to increase water intake and stomach swelling, Shah said, while also affecting the biological process that determines how much food people consume.
The study was published online Jan. 2 in the Journal of the Academy of Nutrition and Dietetics.
Although just less than 15 percent of Americans were obese in the early 1970s, that figure increased to nearly 36 percent by 2010, the researchers said.
To explore a potential connection between slow eating and reduced caloric intake, the team focused on 35 normal-weight men and women and 35 overweight or obese men and women.
During a two-day study period, all were asked to consume the exact same meals under two conditions. The "slow" meal was spread over an average of 22 minutes per meal, involving small bites and deliberate chewing without concern for time. The "fast" meal involved large bites and quick chewing, under the notion that time was of the essence. The average fast-meal time was about nine minutes.
The result: Normal-weight participants were found to consume 88 fewer calories when eating slowly, a decrease deemed "significant." By contrast, the obese/overweight group saw only a 58-calorie reduction during the slow-eating session, which was not considered significant.
The researchers said the obese/overweight group actually consumed less food overall during both the slow- and fast-eating sessions than the normal-weight group. That finding might explain the smaller calorie drop during the first group's slow-eating trial, they said.
Some self-consciousness among the participants might also have affected eating patterns, leading them to consume food in a manner that differed from a private, real-world setting. "There is always the possibility that people will eat differently when they are being observed," Shah said.
Both groups ate less when eating slowly, however, and a notable spike in water intake during the slow-eating test might be a major reason why. When eating slowly, water intake increased by 27 percent among the normal-weight group, and by 33 percent among the overweight/obese group.
Susan Roberts, a senior scientist with the U.S. Department of Agriculture, suggested that the study suffers from a number of analytic flaws.
"First of all, slow eating reduces [calorie] intake by 10 percent in the normal-weight folk and 8 percent in the obese ones," said Roberts, who works at the nutrition research center at Tufts University in Medford, Mass. "The 10 percent is [deemed] statistically significant, whereas the 8 percent is not. However, there is no significant difference between 8 percent and 10 percent, meaning ... there is no difference in the effect of eating speed on [calorie] intake according to whether you are obese or lean."
"More importantly," she added, "the obese individuals in the study substantially under-ate during the measurements, which calls into question whether the results are meaningful and repeatable."
Lona Sandon, assistant professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas, said the study did not control for a number of factors that could have influenced the findings. That makes it impossible to conclude that there is any direct cause and effect between slower eating and lower food consumption, she said.
"However, there are other theories and camps of research that support the theory that we consume less when we eat more slowly," said Sandon, a registered dietitian. "Taking time to enjoy and be more mindful of the food we are eating is associated with eating less."
"[But] it may be a better strategy for preventing weight gain, as opposed to treating overweight and obesity," Sandon said.
To learn more about healthy weight, visit the U.S. National Heart, Lung, and Blood Institute.