Most people would have enjoyed participating in this study by University of Bathresearchers — especially because it involves eating a lot of pizza.
Researchers recruited 14 healthy participants and had them eat pizza on two occasions: one time until they were comfortably full, and the other until they couldn’t eat another bite. The results, as the eternal clickbait goes, will surprise you.
Researchers at the Centre for Nutrition, Exercise and Metabolism at the University of Bath analyzed the blood of participants before and after each meal.
In the ‘eat all you can’ group session, participants ate around 3000 kcal on average, roughly about one and a half large pizzas — about two times more than the other ‘normal meal’ group. However, this varied a lot, as some individuals were able to consume up to two and a half large pizzas in one go. Researchers were surprised to see that even when participants pushed way beyond their usual limits and doubled their calorie intake, they managed to keep the amount of nutrients in the bloodstream within the normal range, at least in the short term.
Essentially, this one overindulgent meal did not seem to make much of a difference, says lead researcher Aaron Hengist.
“We all know the long-term risks of over-indulgence with food when it comes to obesity, type II diabetes and cardiovascular disease, but we know much less about some of the immediate effects ‘all you can eat’ places on the body. Our findings show that the body actually copes remarkably well when faced with a massive and sudden calorie excess. Healthy humans can eat twice as much as ‘full’ and deal effectively with this huge initial energy surplus.”
For instance, blood sugar was no higher than after a normal meal, and blood lipids were only slightly higher. The one major difference was the amount of insulin in the blood, which was 50% higher for the large meal than the normal one.
The study also analyzed the participants’ appetite and found that after eating the big pizza meal, participants felt sleepy, lethargic, and had no desire to eat anything else, even dessert. This was somewhat surprising, researchers note, because reward centers in the brain are typically food-specific, so eating a lot of pizza might not be expected to change the desire for sweet food.
This study should not be interpreted as ‘eat all you want and all is OK’. All the participants in the study had a healthy body mass index and were generally healthy — this was a one-off for them, and it was a very small sample size, insufficient to draw any general conclusions.
Still, given all the interest in nutrition and how people tend to overeat, we know surprisingly little about maximal eating, says Professor James Betts, who oversaw the work.
“We know that people often eat beyond their needs, which is why so many of us struggle to manage our body weight. It is therefore surprising that no previous research had measured the maximal capacity for eating at a single meal in order to understand how the human body responds to that challenge.”
“This study reveals that humans are capable of eating twice as much food as is needed to make us feel ‘full’, but that our bodies are well adapted to an excessive delivery of dietary nutrients at one huge meal. Specifically, those tested in this study were able to efficiently use or store the nutrients they ingested during the pizza-eating challenge, such that the levels of sugar and fats in their blood were not much higher than when they ate half as much food.”
The study could also help reconcile research about how and when we eat. For instance, recent studies have shown that people who eat one big breakfast burn more calories than those who don’t.
While the question of the long-term effects of one-off big meals is still unanswered, it’s encouraging to know that if your diet is healthy overall, one exception probably won’t make a huge difference.
“The main problem with overeating is that it adds more stored energy to our bodies (in the form of fat), which can culminate in obesity if you overeat day after day. However, this study shows that if an otherwise healthy person overindulges occasionally, for example eating a large buffet meal or Christmas lunch, then there are no immediate negative consequences in terms of losing metabolic control.”
Alexandra is a naturalist who is firmly in love with our planet and the environment. When she's not writing about climate or animal rights, you can usually find her doing field research or reading the latest nutritional studies.