Though the impact on energy intake of reducing energy density is well known, there is less scientific evidence on how changes in texture can lead to reductions in eating rate. Through mathematical modelling and a human intervention trial, "RESTRUCTURE: Developing and implementing innovative and evidence-based food design principles to moderate energy intake" will unravel the links between physical properties like food texture, the speed of eating and energy intake.
In recent years, ultra-processed foods (UPF) have become one of the most discussed nutrition topics world-wide. Several studies have shown that diets high in UPFs are associated with overweight and obesity and diet-related chronic diseases such as type 2 diabetes and coronary heart disease. One randomized controlled trial has confirmed this finding where people consumed more energy and gained weight (~ 1 kg) on a two-week UPF diet compared to an unprocessed food diet. However, to date it is unknown what aspects of UPF drive this effect on calorie overconsumption and health.
Based on previous research we know that certain food properties drive calorie consumption. Two of these important food properties are thought to be food texture (or structure such as liquid, soft, hard, elastic etc.) and energy density (the number of calories contained in 100 g of food), may make people eat more of them.
Energy density affects how much calories people consume as people tend to eat a fixed amount or portion of a specific food, not adjusting for the amount of energy it may contain. For example, a person may commonly eat one bowl of yoghurt in the morning, when served a different type of yoghurt (with more calories) the person will not adjust the amount of yoghurt in the bowl accordingly and eat the amount or volume that he/she is used to while consuming more calories. Certain food textures require less chewing before a bite of food can be swallowed and are therefore faster to eat.
Previous research has shown that the speed of eating affects the speed at which we feel full, which in turn determines how much food we eat during a meal. When food is eaten quickly, people tend to eat more. The texture of UPF may therefore play an important role in driving food or calorie overconsumption of these foods. Eating more calories than the body uses leads to storage of energy in the form of bodyfat and weight gain over time. For example, the image below shows that the same number of grapes is consumed 12 times faster when squeezed into a juice compared to when eaten as whole grapes. When eating the whole grapes, someone will most likely feel full far before finishing the entire portion of 1 kilogram. This shows that the type of food and the speed of eating may influence how much we consume of the food.
Although the effect of food texture and eating rate on food and energy intake has been studied extensively on a meal-level using different types of foods, less is known about how the eating rate of UPF diets influences food and energy intake over the longer-term (i.e. across weeks).
The RESTRUCTURE project was initiated in 2021 to investigate the food texture properties that moderate eating speed and energy intake. The project was extended in 2022 to further explore whether meal texture influences daily energy intake over two 14-day periods with diets that are consumed at a faster or slower eating speed. This large randomized controlled trial was conducted in 2024 with the aim to determine the effect of eating rate (ER) of ultra-processed food diets (UPF fast ER vs UPF slow ER) on energy intake across a two-week period. The secondary objectives are to compare any changes in body composition and other pre-defined markers of metabolic health that occur over when consuming ultra-processed diets with either a slow or fast eating rate. You can read the clinical trial registration here and the pre-data analysis scripts and detailed study methods here.
Food texture and energy density are not the only possible mechanisms for how UPFs may contribute to poorer health outcomes. There are many ideas as to why diets high in UPFs may lead to poor health outcomes. For example, there have been suggestions that UPFs could disrupt blood sugar levels (glycaemic homeostasis), fat metabolism, and gut microbiome and affect certain appetite hormone levels. Additionally, there are also some hypotheses suggesting that UPFs may impact our health because of food additives. However, none of these hypotheses or ideas have been supported by data. One of the main outputs of the RESTRUCTURE project is to design a controlled, high-quality intervention trial to get more data precisely on how processed foods may impact our bodyweight and overall metabolic health
