Can eating food that needs more chewing help weight loss?
 The texture of food can affect how full we feel, and therefore potentially help those struggling with obesity to lose weight by reducing their food intake, according to a new study from Leeds University. NHS data shows around 64 percent of adults in England are overweight or obese. Reducing hunger cravings through appetite control and feelings of fullness is one way to tackle the problem. The study discovered food that is both solid and “high viscous” (think eating apples rather than drinking apple juice) could “significantly reduce hunger and promote satiety [the feeling of being full], when compared to liquid and low-viscous food”. We spoke to the people behind the study, as well as other experts, to find out how choosing food with more texture could help with weight loss. What makes us feel full? Explaining how texture could influence our feeling of fullness, the British Nutrition Foundation’s Helena Gibson-Moore says: “The feeling of fullness and the suppression of hunger for a period of time after a meal… occurs due to a number of bodily signals that begin when a food or drink is consumed and continue as it enters the gut and is digested and absorbed. These satiety signals… are generated in response to a number of things, including the sensory experience such as the appearance, smell, taste and texture of the food or drink.” What’s the research? Professor Anwesha Sarkar and PHD student Ecaterina Stribitcaia at Leeds University conducted a study analysing previous research on the subject and applying strict criteria to it: A total of 8,530 studies were narrowed down to 23, to examine the relationship between a food’s texture and how full people feel after consuming it. In all 23 studies, the participants were asked to consume food where the only difference was the texture, for example a chicken breast that was steamed and solid versus one that was blended and soft. They predicted that the results would show “higher textural characteristics would lead to greater suppression of appetite, reduced food intake and gained satiety”. So is this what they found? How does this help people who need to lose weight? After analysing the data, they found their predictions were correct. “The results showed that solid foods decreased hunger significantly compared to liquid ones. High viscous foods significantly increased fullness compared to low viscous ones”. How this might be used to adapt our diet to make us feel fuller for longer is described by Dr Keri McCrickerd, Senior Research Fellow at the Singapore Institute for Clinical Sciences (SICS), Agency for Science, Technology and Research (A*STAR), who has carried out her own study. “We found that people are quite sensitive to changes in the texture of foods and drinks. Even subtle changes to things like thickness, chewiness and creaminess are noticed, and can change how filling a person expects that food or drink to be. “Most importantly, we found the expectations generated by changing a food’s texture impacted things like the portion a person picked and how filling they experienced the foods to be. Often it was the thicker and chewier versions that were expected to be more filling, consumed in smaller portions and experienced to be just as satisfying.” So which foods will make us feel fuller for longer? “It will be difficult to pinpoint a set of ingredients”, say Sarkar and Stribitcaia. “We can say that solid and more viscous foods, such as steamed chicken, will leave people fuller for longer. From a perspective of more complex food texture… further research is required, which we are currently work on”. Do some nutrients make us feel fuller for longer? Eating for satiety isn’t all about texture. Protein is good at filling us up, and Gibson-Moore explains that, “Foods that are high in fibre may also enhance feelings of satiety. So including protein foods, such as beans, pulses, eggs, fish, chicken (without the skin) or lean meat, and plenty of high-fibre foods, such as wholegrain bread and cereals, beans, pulses and fruit and vegetables, in meals may help us suppress feelings of hunger until the next meal.” As for foods that do the opposite – leave you immediately hungry – McCrickerd says calorific beverages are the worst offenders. “Soft drinks and flavoured teas and coffees that are high in sugar are known to be not very filling, despite the calories they can contain. Part of the reason for this is that we think of such products as thirst-quenching or something to be consumed in a social context, and don’t expect them to be filling. Although their volume can be high, they are also fast to consume and generally low in protein and fibre.” Is it all in the mind? “Satiety is dependent on more than just the metabolic effects of nutrients in the gut, and psychology plays a part”, says Gibson-Moore. Sarkar and Stribitcaia agree. “It is challenging to pinpoint the exact cause of the feeling of fullness, because the physiological and psychological consequence of eating a food of a certain texture is a very complex milieu [environment], and a lot of factors jointly can be affected by food texture… The key physical mechanism is linked to ‘oral residence time’ (ORT). Generally, a solid or highly viscous food stays in the mouth for longer and gets chewed sufficiently to allow time to mix with saliva before being swallowed, whereas for a liquid the ORT is very low. The longer the ORT achieved by manipulating food texture, the more time the body (both psychologically and physiologically) gets to sense it and trigger the feeling of fullness. The cognitive aspect is very important.” However, they are keen to stress that they did not investigate this aspect. What food comes wrapped in can also convince us it’s going to be filling, according to McCrickerd. “Product labelling, taste, texture and apparent size can all affect our expectations about how filling a food or drink is going to be, and when we believe it is going to be more filling we are more likely to pick smaller portions or feel fuller after consuming it”, she says. Should you buy more high-texture food? Before you change your shopping list to include more texture-heavy (and protein-packed) foods, there’s a bit of a disclaimer: there’s still more research required. “It’s still not clear whether changing the texture of the foods we eat will have a meaningful impact on our dietary behaviours or weight over time”, says McCrickerd. “Most of the research to date has been from relatively small and short-term studies that have modified the texture of one food item and looked to see how people’s eating behaviours are affected over one meal or day. Longer-term studies are needed to see how sustainable the effects of texture-enhanced foods are across days and weeks of consuming them, and whether this approach can complement existing strategies to reduce the portion size and calorie content of popular foods and beverages”, she concludes.