Plenty of studies have looked at the long-term health effects of excessive calorie intake, which include increased fat storage, impaired endocrine control, and changes in muscle.
However, little is known about how our bodies cope with this overeating, and whether it has any impact on our overall health.
Humans have a tremendous ability to eat a heavy meal over a long period of time. For example, members of the “Masa” tribe participate in the Guru Walla Festival, which is a traditional fattening festival where they try to gain as much weight as possible, by eating as much food as possible.
Many members gain 11 kg of fat in just two months, by eating roughly 8,700 calories a day – more than 3 times what is recommended for most adults per day.
While this is an extreme example, it shows that our bodies are easily able to overeat – that is not necessarily a good thing. Even as little as 24 hours of overfeeding, it can have some negative consequences for our health, including elevated blood sugar concentrations.
In the study, researchers at the University of Bath wanted to understand how much humans can eat when they exceed the fullness point, and to know the effect of that on the body, by measuring the effect of overeating on the metabolism in the hours after a meal.
They studied a group of 14 healthy men, between the ages of 22 and 37. In one experiment, they were asked to eat as much pizza as possible until they were satisfied. And they ate roughly 1,500 calories on average – just less than one large pizza.
On a separate day, they were asked to eat until they were no longer able to, bypassing the normal feeling of fullness. Remarkably, they were able to eat nearly double – about 3,000 calories on average, although some managed to eat nearly two and a half large pizzas (4,800 calories).
This indicates that when you feel full, you are probably half full.
Blood samples were taken at regular intervals for 4 hours after the start of the meal, to see how the body was adjusting. Surprisingly, despite eating twice as much food, there was only a slight increase in blood sugar and lipid levels in the blood.
The ability to keep blood sugar and fat levels in the normal range indicates how healthy a person’s metabolism is. It can also show the risk of developing diseases, including type 2 diabetes or cardiovascular disease.
In these physically active and healthy people, the body is able to control sugar and fats in the blood after eating a large meal by working a little more than usual to control metabolism.
It turns out that hormones released from the gut and pancreas (including insulin) helped the body regulate blood sugar levels. The heart rate increased after the meal, confirming that the body was working harder to keep things under control.
The research team measured how people felt during the post-meal period, by looking at satiety, drowsiness, and cravings for certain types of foods.
And while we often feel we have an extra space for dessert, study participants had little craving for anything (even sweetened foods) when they passed the feeling of fullness phase – even 4 hours after the meal. They also found that people felt sleepy and less energetic after eating a lot of food.
The results revealed that a single meal of overeating does not cause much harm to your health – although overeating for 24 hours appears to have an effect. So the focus of further research may be on understanding how our bodies handle the next meal after a binge eating.
Understanding how the body easily copes with times of excessive calorie intake helps us understand what goes wrong in the long term. Healthy people depend on the body’s ability to work more diligently in times of need (by increasing insulin, gut hormones, and heart rate), to maintain metabolic control.
And when we frequently eat too many calories at every meal, metabolic syndrome (a combination of high blood pressure, diabetes, and obesity) will develop and the body becomes unable to respond to these situations.
And before the study begins, expect the body to suffer from massive caloric surplus from overeating. The results demonstrate the body’s remarkable ability to handle the stress of eating a lot of food, by carefully regulating blood sugar concentrations and blood pressure.
And throughout history, the human body has had to adapt to periods of famine and abundance – this study is further evidence of this evolutionary adaptation.
Although we focused on healthy young participants, it will now be important to look at how the body deals with overeating in people who are overweight or at risk of developing diseases, such as type 2 diabetes.
But while overeating can sometimes be normal – and not a major threat to our health – it is important to emphasize that eating more than we need on a regular basis is unhealthy. This is partly because eating more calories than required over a long period of time will lead to weight gain and may lead to metabolic disease.