Eating slowly may aid prevent obesity, claim researchers. This is based on research carried out in Japan, the Guardian reported.
The study was conducted by researchers from Kyushu University in Japan, with funding from the Ministry of Health, Labour and Welfare of Japan.
The researchers discovered that people who said they ate slowly or at normal speed were less likely to be obese at the end of a 6-year study, than those who said they ate quickly.
The study used data from health checks with 59,717 Japanese people who had type 2 diabetes. The scientists wanted to see if eating speed and some other eating behaviours like taking snacks after dinner, affected obesity.
Very few people changed their eating speed during the course of the study. They discovered that people who ate slower were less likely to be obese; but we don’t know from this study whether changing your eating speed would work as a weight-loss plan.
Theoretically, it makes sense that a person may tend to eat less if he/she eats more slowly. Experts say that when we eat quickly, our bodies don’t have time to register the hormonal changes that signal when we are full.
Eating more slowly may help to decrease the amount of calories we eat but because this study didn’t look at calorie intake or diet, we don’t know if the intake of calorie explains the discoveries.
Researchers wanted to see how eating speed over time, and a range of other eating behaviours, affected people’s likelihood of being obese. They focused their analysis on people with type 2 diabetes as obesity is a known risk factor for this condition. The researchers felt this group could benefit most from any observations.
Observational studies can demonstrate links between factors such as eating speed and obesity, but they cannot prove that one factor (such as eating quickly) directly causes another (such as obesity). A wide range of other unrecorded factors (amount of food consumed, physical activity, etc) may affect the results.
Researchers used health check data collected over a 6-year period from 59,717 Japanese people aged over 40 who had been diagnosed with type 2 diabetes. As part of a government scheme, all adults over 40 enrolled with health insurance companies are invited to attend health checks to detect risk factors for obesity and metabolic syndrome (a combination of diabetes, high blood pressure and obesity).
At the health checks, people were asked about a range of eating behaviours, including:
- whether they ate at a fast, normal or slow rate
- whether they regularly (3 or more times a week) ate within 2 hours of bedtime
- whether they regularly ate snacks after dinner
- whether they ate breakfast
They also had their body mass index (BMI) calculated, their waist size measured, and were categorised as obese or not obese. It is worth noting that in Japan a BMI of 25 or over is considered obese, whereas in the UK 25 to 29 is overweight and only 30 and above is considered obese.
READ ALSO: Brain Foods For Mental Alertness
People were offered annual health checks, but as they entered the study at different stages after their diabetes diagnosis, most did not have 6 sets of results.
The researchers used a variety of statistical models to look at how people’s stated eating speed, and any change over the time of the study, influenced their chances of being obese at the end of the study.
They considered these potential confounders:
- obesity status at the previous checks
- participant age
- use of diabetes medicine
What were the basic results?
People who said they ate quickly at the start of the study were more likely to be obese at the start of the study:
- 8% of people who said they ate fast were obese
- 6% who said they ate at normal speed were obese
- 5% who said they ate slowly were obese
Fast eaters were also more likely to be men who eat dinner within 2 hours of bedtime. When compared to fast eaters, by the end of the study:
- normal speed eaters were 29% less likely to be obese
- slow eaters were 42% less likely to be obese
Various eating habits also increased risk of obesity. Compared to people who ate dinner within 2 hours of sleeping (at least 3 times a week), those who didn’t were 10% less likely to be obese (OR 0.90, 95% CI 0.86 to 0.94).
Only 171 people (0.29% of quick eaters) changed from fast eating at the start of the study to slow eating at the end, and 92 people (0.15% of slow eaters) changed from being slow eaters to quick eaters.
How the researchers interpreted the results
The researchers said their discoveries “indicate that weight loss can be supported through the reduction of eating speed”. They also say that eating dinner more than 2 hours before sleeping, not snacking after dinner and always having breakfast may also help weight loss.
There are limitations to this study that we need to take into account:
- The study did not measure how much people ate, so we don’t know if people who ate more slowly were eating fewer calories than those who ate quickly.
- The study included mostly working-age people who were motivated to attend health checks, so we don’t know if the results would apply to older or less health-conscious people.
- The study didn’t assess people’s socioeconomic group, which might have had an effect. For example, if you have to eat meals during short breaks in a long working day, you may eat quicker than people who can afford to take their time. This may mean that people’s relative levels of deprivation could affect the results.
- The study relied on people’s own reports of how quickly they ate, without defining speed as other than fast, normal or slow. One person might describe themselves as a slow eater, but eat at a speed that seems fast to someone else.
READ ALSO: 10 Foods That Fight Belly Fat
There may be limits to how the findings apply to the UK, in terms of the population diet, lifestyle and risk factors for obesity. In Japan the BMI threshold for obesity (>25) is lower. It corresponds to the UK threshold for overweight. Prevalence of obesity according to the UK threshold (BMI>30) is much lower in Japan. That means the results may not translate directly.
Few people in the study changed from fast to slow eating, so the proposed benefits from eating slowly are only theoretical. We don’t know whether people would lose weight if told to eat more slowly, or how easy it is to change eating speed.