A study of people consuming all-you-can-eat pizza has found the male body copes “remarkably well” when faced with a sudden increase in calories.


The research by the University of Bath asked healthy men aged between 22 and 37 to eat until they were “comfortably full” on one occasion and eat until they could not “manage another bite” on another.

Those who volunteered for the trial consumed almost twice as much pizza when pushing beyond their usual limits, doubling their calorie intake. But the study found the amount of nutrients in their bloodstream kept within normal range.

Researchers say this shows that if an otherwise healthy person overindulges occasionally there are no immediate negative consequences in terms of losing metabolic control.

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Aaron Hengist, of the University of Bath, said: “We all know the long-term risks of overindulgence with food when it comes to obesity, type 2 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.”

In the study, published in the British Journal of Nutrition, the average calorie intake in the all-you-can-eat trial exceeded 3,000 – around one and a half large pizzas. Some individuals were able to consume up to two and a half large pizzas in one sitting – well beyond standard adult guidelines for calorie intake in one day.

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
Prof James Betts

Results showed that after eating to excess, blood sugar levels were no higher than after a normal meal, though the amount of insulin in the blood was 50 per cent higher than usual. Blood lipids were only slightly higher despite having consumed more than twice as much fat than eating until comfortably full.

Hormones released by the gut to stimulate insulin secretion and increase feelings of fullness were changed the most by overeating.

Four hours after overindulging, the participants felt sleepy and lethargic, and did not have a desire to eat anything else, including sweet foods.

Professor James Betts, who oversaw the work, said: “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.”

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Prof Betts said the main issue with overeating is it adds more stored energy to the body in the form of fat, which can result in obesity if people eat 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,” he added.


The researchers acknowledged their study involved healthy young men so they plan to investigate whether similar effects occur in women and for overweight and older people.

What happens to your body after eating Christmas dinner?

As you prepare to start your festive feasting, it’s probably best not to think about the discomfort that may follow. Here, we remind you of what lies in store in the 24 hours following your day of overindulgence. Recent South African research suggests one Christmas meal could fuel a 1.7-day hike in the Himalayas. But don’t focus on the calories – this is a day of celebration!

First 5 minutes

Alcohol absorbs rapidly into the bloodstream and will hit you five to 10 minutes after your first sip. The small intestine absorbs most of the alcohol, while 20 per cent enters through the stomach. Alcohol dilates blood vessels, particularly the capillaries under your skin, making you feel warm.

20 minutes

The average stomach capacity is around one litre, but it takes 20 minutes for ‘full’ signals to reach the brain from the gastrointestinal tract, after you first starting eating. By then, you may already have overeaten. Eating and drinking too fast makes you belch as you swallow excess air.

As you eat, the food hikes up your blood sugar levels. In response, your pancreas will start producing the hormone insulin, which will convert the glucose into a storable form called glycogen. The resulting drop in your blood sugar levels makes you feel overwhelmingly tired.

One hour

After eating, more blood flows to the digestive tract. To aid digestion, your heart and metabolic rate go up, accompanied by a slight increase in body temperature, making you sweat and feel more tired. To make matters worse, rich foods are harder to process, and alcohol slows digestion.

A heavy meal rich in protein and fat can sit in your stomach for two to three hours, making you feel bloated. Flatulence is partly triggered when the body’s enzymes can’t deal with certain substances such as raffinose, a complex sugar found in brussels sprouts and other brassicas.

Three hours

It takes about three hours for the body to break down a 250ml glass of wine, but you’ve probably drunk more than that. Is it time for the cheeseboard? Combined with the carbs in crackers, the amino acid tryptophan in cheese could make you crash out.

Six hours

It takes six to eight hours for food to pass through the stomach and the small intestine, before reaching the large intestine. The body digests meat into amino acids, which are absorbed through the small intestine and into the blood.

24 hours

With any luck, your hangover, caused largely by dehydration from alcohol’s diuretic nature, will have eased by now. The body may finally start eliminating undigested food, having absorbed water and minerals, and stored excess fat.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.