New diet and eating habit recommendations are constantly emerging as scientists and dieticians try to combat rising obesity rates seen worldwide, prolonging meal duration is just one example of this. According to the World Health Organisation (WHO), globally, adult obesity has more than doubled since 1990, and adolescent obesity has quadrupled.

The WHO criteria for defining obesity or overweight in adults are:

• Overweight is a BMI greater than or equal to 25; and
• Obesity is a BMI greater than or equal to 30.

Obesity and being overweight have been linked to serious health risks, including type 2 diabetes, heart disease, stroke and certain cancers. Consuming food at a quicker pace has been linked to a higher risk of obesity and weight gain.

Researchers from the Fujita Health University in Japan recently published a study in the Open Access journal Nutrients investigating the effects of meal type on meal duration.

Dietary management of obesity

Obesity and being overweight are complex conditions that can be caused by a range of factors, including diet, lack of physical activity, genetics and environmental factors.

Environmental factors are a big risk factor for developing obesity; food insecurity and unhealthy eating habits learnt in childhood can contribute to the overconsumption of cheaper, less nutritious food. Moreover, there is a strong link between mental health and obesity. Food can become a coping mechanism to help manage stress, depression and anxiety.

Eating foods rich in fat and sugar activates the dopaminergic system in the brain, which is responsible for motivation and reward. These factors can make it difficult to manage obesity and for individuals to follow specific diets. Moreover, because of this, dieticians and scientists have been looking for simple and practical ways to improve eating habits. This includes eating slowly, which can reduce food intake and calories.

Eating slowly to reduce the risk of obesity

Appetite and food intake are regulated by hormones such as ghrelin, which controls hunger.  Ghrelin is produced and released mainly by the stomach. It is released when the stomach is empty. Following a meal, ghrelin is suppressed, and a variety of hormones are released to signal fullness and regulate energy balance, including leptin, insulin and gut peptides. However, this process can take up to 20 minutes; eating slowly allows these hormones extra time to relay signals, preventing overeating.

Eating slowly is not easy to incorporate into certain lifestyles. Because of this, researchers from Japan investigated the factors influencing meal duration, particularly how meal type influences meal duration.

Meal type influences meal duration.

The researchers analysed meal duration, number of chews and bites and chewing tempo among 41 participants (18 males and 23 females). The participants were recruited from the faculty and staff of Fujita Health University.  Additionally, the participants had to be between the ages of 20 and 65 years. Participants with anorexia nervosa, bulimia nervosa, BMI > 30, or preexisting diabetes or kidney disease were not included.

The participants were initially asked to fill out food frequency questionnaires to estimate energy and nutrients in their diets. Moreover, the participants were also asked to assess handgrip strength to indicate upper body strength and overall muscle strength.

The researchers assessed meal duration using two different meals with similar calorie intake but differing nutritional value and two eating sequences. This included pizza (301 kcal) and hamburger steak with rice and broccoli served in bento style (Japanese packed lunch) (304kcal). The participants were first assessed whilst eating pizza using a Bitescan device to analyse the meal duration, number of chews, number of bites and number of chewing tempos. Additionally, the researchers used a stopwatch to confirm eating duration, as well as recording the session via video recording.

“Eating slowly is widely recommended for obesity prevention. But people often don’t know how to implement this advice. Our study shows that simply choosing the right type of meal—such as a bento instead of fast food—can naturally extend meal duration and encourage more mindful eating.” – Professor Katsumi Iizuka, author on the study.

After 4 weeks, the researchers changed the meal to hamburger steak with rice and broccoli (bento) and instructed to eat the broccoli first, followed by the rice, and then the hamburger. The researchers then measured the meal duration as explained above.

The final meal assessment was completed 4 weeks later, where the bento was again served to the participants, but they were instructed to eat the rice first, then the hamburger steak and then the broccoli.

Meal type affects meal duration.

The researchers identified that participants consumed the pizza significantly faster than the bento. The participants demonstrated shorter meal durations and fewer chews when eating pizza than when eating bento.

Bento meals were consumed using chopsticks and had individual components, promoting slower eating. In addition, they identified that eating vegetables first or last did not affect meal duration. The study also identified differences between men and women. Men generally ate faster and chewed less than women; however, in both groups, the bento took longer to eat.

Professor  Katsumi  Iizuka explains that

“One key factor affecting meal speed is how the food is served and eaten. Bento meals are served in small portions that need to be picked up with chopsticks, which slows down the process. In contrast, pizza is eaten by hand and is often designed to be eaten quickly. This difference in serving style plays a big role in how fast people eat.”

The researchers conclude that meal type does have a significant effect on meal duration and that it’s important to pay attention to the food we choose to consume to prevent the development of obesity. Additionally, they note that future research should focus on meal duration and contents in the everyday setting of obese individuals. Moreover, they explain that psychological and environmental aspects should also be considered.

“If we want to help people eat more slowly, we should focus less on telling them how to chew and more on helping them choose meals that require slower, more deliberate eating; this could be a simple yet powerful tool in our fight against obesity and related diseases,” – Professor  Katsumi  Iizuka.

If you would like to read more or submit research about reducing the risk of obesity, please see the Nutrients section: Nutrition and Obesity.