The data from researchers at the Nestlé Research Center and Wageningen University in the Netherlands aims to unravel the complex relationship between the foods we eat and our eating behaviours – including food consumption rates, bite size, and caloric intake.
Led by Ciaran Forde from the Nestlé Research Center in Switzerland, the team report two new studies that together begin to unravel how the sensory properties of various foods and meals influence eating behaviour and food intake.
“The current obesogenic food environment is characterized by energy dense, softly textured foods that can be eaten quickly,” explained the research team, writing in the journal Appetite.
“Previous studies suggest that oral processing characteristics such as large bite size, low number of chews and low orosensory exposure contribute to the low satiating efﬁciency of these foods”
"The evidence from these studies provides new insights into how different foods may impact eating behaviours, such as bite size and chewing time. These, in turn, can also impact feelings of fullness and food intake," added Forde.
"Our ultimate goal is to help consumers control their energy intake,” he said. “With the knowledge gained from these studies, we can make more pleasurable and satisfying meals that promote fullness with fewer calories.”
In their first study, Forde and his team said their data revealed ‘surprising differences’ in the way foods were consumed. For example, the average number of bites for each food varied from 5 bites (for raw tomatoes) to 33 bites (for tortilla chips) – a rather surprising six-fold difference.
The second study then examined whether foods that require more chewing and which stay in the mouth longer, promote greater feelings of fullness – and therefore reduce energy intake.
“Foods that were consumed in smaller bites, were chewed for longer and were expected to impart a higher satiation,” they confirmed.
“This information may be used to design foods meals lower in energy and higher in satiating efﬁciency per kcal consumed.”
The first of the studies tested the oral processing characteristics – including chew rate and bite size – of 35 solid, savoury foods that often comprise hot meals.
Examples included a variety of vegetables, meat and prepared foods (such as chicken, tofu, lasagne, pizza) and snack foods (like tortilla chips, fish fingers).
Participants were asked to eat a standard 50 g amount of each food item, 7 of which were tested over 5 consecutive days.
Video recordings of the volunteers eating the food were then used to calculate the eating rate (g/min), chew rate (chews/min), average bite size (g/bite), average chews/bite and overall oral duration time (seconds) for each of the 35 test foods.
The team found large variations between the number of chews – ranging from 27 chews for mashed potatoes, to 488 chews for tortilla chips – and also found that softer foods (such as mashed carrots, lasagna and canned tomatoes) were eaten in larger bite sizes with fewer chews per bite, resulting in a much faster eating rate.
The Nestlé scientists concluded that foods consumed in smaller bite sizes which were chewed longer resulted in slower eating rates and higher expected fullness among study volunteers.
Based on this they then formed and tested a second theory – whether foods that require more chewing, and which stay in the mouth longer, promote feelings of fullness and therefore reduce energy intake?
In this second study a test meal of steak and gravy, carrots and potatoes was adapted into whole and pureed textures with gravy of high and low flavour intensity. The meal was served to four groups of volunteers to consume ad libitum they were comfortably full.
Food intake was measured and compared across each group and meal condition, and the duration of each individual’s mealtime was recorded to enable comparison of eating rates.
Participants that ate whole vegetables and steak consumed about 10% less than those who ate the mashed vegetables and steak pieces. The difference in gravy taste intensity resulted in a higher intake only with the mashed meal. Overall, the mashed meal was consumed about 20% faster than the whole meal - the equivalent of an extra 10g/minute more of food eaten.