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Eating slowly (and not close to bedtime) may help prevent weight gain, study finds

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Use chopsticks, if you don't normally use them, for slower, more “mindful” eating.

People who linger over their meals and eat slowly are less likely to be obese after six years than those who gulp down their food quickly, a new study from Japan reports.

The study also found lower rates of obesity among people who eat their final meal of the day at least two hours before bedtime, who avoid after-dinner snacks and (to a lesser extent) who always have breakfast. 

This study comes with all sorts of caveats (more about those in a bit), but its findings are also supported by other research that has suggested how and when we eat can help us maintain a healthier weight and waistline.

“Interventions aimed at altering eating habits, such as education initiatives and programmes to reduce eating speed, may be useful in preventing obesity and reducing the risk of non-communicable diseases,” the authors of the new study conclude. 

Study details

For the study, which was published earlier this week in the journal BMJ Open, researchers at Kyushu University analyzed health insurance data collected from 2008 to 2013 for almost 60,000 Japanese adults over the age of 40 who had been diagnosed with type 2 diabetes. The researchers chose that particular group of people because obesity is a known risk factor for type 2 diabetes. 

During the duration of the study, the participants underwent regular checkups, which included body mass index (BMI) and waist circumference measurements. At the checkups the participants were also asked questions about their eating habits, including whether they ate at a fast, normal or slow rate; whether they regularly ate dinner within two hours of going to sleep; whether they regularly snacked after dinner; and whether they regularly skipped breakfast. (“Regularly” was defined as three or more times per week.)

At the start of the study, more than half (56 percent) of the respondents said they ate at a normal speed, while more than a third (37 percent) said they tended to gobble up their food quickly. Only about 7 percent reported that they lingered over their food.

Any self-reported changes in the participants’ eating speed were recorded at subsequent checkups.

Key findings

With the aid of various statistical models, the researchers used the collected information to see if the participants’ eating speed — including changes in it — influenced the likelihood of them being obese at the end of the study. They also adjusted for various confounding factors, such as age and BMI at the start of the study.

They found that the people who were least likely to be obese when the study began were those who said they ate slowly. Specifically, 45 percent of the participants who said they ate fast at the start of the study were obese, compared with 30 percent who said they ate at a normal speed and 22 percent of those who said they ate slowly. 

An association between eating speed and obesity was also observed at the end of the study. After six years, the normal-speed eaters were 29 percent less likely and the slow eaters were 42 percent less likely to be obese than the fast eaters.

(Obesity in Japan is defined as a body mass index of 25 or higher. That’s lower than in the United States, where individuals are considered obese if their body mass index is 30 or higher.)

The study also found associations between other eating habits and the risk of obesity. The participants who regularly ate dinner within two hours of sleeping were 10 percent more likely to be obese than those who didn’t, while those who regularly munched on after-dinner snacks were 15 percent more likely to be obese.

Skipping breakfast had a much smaller impact. The participants who said they regularly did so were just 7 percent more likely to be obese.

Limitations and implications

As already noted, this study has many limitations. To begin with, it’s an observational study, which means it can’t prove a direct cause-and-effect relationship between eating slowly — and any of the other eating habits — and obesity. Furthermore, the participants self-reported their eating habits, and what is “slow eating” to one person may not be to another. Also, the study didn’t measure how much the participants ate. Perhaps the people who lingered over their food were also eating less — and thus consuming fewer calories.

It’s also not clear if the findings would apply to people living in different countries, where diet, lifestyle and obesity rates differ.

Still, findings from other studies support the idea that eating speed can affect BMI and obesity.

“A possible reason for this association is that fast eaters may continue to eat until they feel full despite having already consumed an adequate amount of calories, and the combined effect of eating quickly and overeating may contribute to weight gain,” write the authors of the current study. “In contrast, eating slowly may help to increase feelings of satiety before an excessive amount of food is ingested.”

Previous research has also shown that eating after dinner or within two hours of sleeping are risk factors for metabolic syndrome, a group of conditions (such as high blood pressure, high blood sugar and excess fat around the waist) that raise the risk of heart disease, stroke and type 2 diabetes.

Mindful tips

Nutritionists at Harvard University offer these tips for people who want to try slower, more “mindful” eating:

  • Set your kitchen timer to 20 minutes, and take that time to eat a normal-sized meal.
  • Try eating with your non-dominant hand; if you’re a righty, hold your fork in your left hand when lifting food to your mouth.
  • Use chopsticks if you don’t normally use them.
  • Eat silently for five minutes, thinking about what it took to produce that meal, from the sun’s rays to the farmer to the grocer to the cook.
  • Take small bites and chew well.
  • Before opening the fridge or cabinet, take a breath and ask yourself, “Am I really hungry?” Do something else, like reading or going on a short walk.

FMI: You can read the Kyushu University study in full on the BMJ Open website.

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