UK Edition
Humans have an in-built calorie counter that automatically clocks how much energy is in our food and helps us eat less fatty foods, a study has found.
Our brains seemingly have the inherent ability to tuck into a meal and know how calorific it is and and our appetites adjust accordingly.
The findings challenge the current nutritional theory that humans are completely unaware of how many calories are in their food, making us vulnerable to overeating, whether it is a calorie-dense pasta dish or an energy-poor salad bowl.
Researchers from the University of Bristol say people were not told whether they were eating a low or a high-energy meal, and the findings showed that humans are smarter eaters than we have previously given ourselves credit for.
Lead author Annika Flynn, doctoral researcher in nutrition and behaviour at the University of Bristol, said: "For years we've believed that humans mindlessly overeat energy-rich meals.
"Remarkably, this study indicates a degree of nutritional intelligence whereby humans manage to adjust the amount they consume of high-energy density options."
The new study looked at data from a 2019 trial where 20 healthy adults who were in hospital for four weeks were given standard, everyday meals such as a chicken salad sandwich with fig roll biscuits or porridge with blueberries and almonds.
The original study looked at ultra-processed foods and healthier options and each meal had a known amount of calories as well as sugar, fat, fibre and macronutrient content.
Writing in their study, the researchers speculated that there is likely to be a calorie turning point where a person registers that their meal is packed with calories and they then subconsciously decide to eat less.
Ms Flynn said: "For instance, people ate smaller portions of a creamy cheese pasta dish, which is an energy-rich meal, than a salad with lots of different vegetables which is relatively energy-poor."
'Hidden complexity to how humans interact with energy-rich foods'
Co-author Jeff Brunstrom, professor of experimental psychology at the University of Bristol, said: "This research gives added weight to the idea humans aren't passive overeaters after all, but show the discerning ability to moderate how much of an energy-rich meal they consume.
"This work is particularly exciting as it reveals a hidden complexity to how humans interact with modern energy-rich foods, something we've been referring to as 'nutritional intelligence'.
"What this tells us is we don't seem to passively overconsume these foods and so the reason why they are associated with obesity is more nuanced than previously thought.
"For now, at least this offers a new perspective on a longstanding issue and it opens the door to a range of important new questions and avenues for future research."
The findings are published in The American Journal of Clinical Nutrition.