Here’s What Buffets Do to Your Body and Brain

How much food your stomach can hold may be the reason why you're having trouble losing weight.

You may eat with your eyes first, but both your stomach and your mind have a big say in how much you consume before you feel full. A July 2020 study in the journal Gastrointestinal and Liver Physiology suggests that while your stomach volume can lead you to eat more calories at a meal, your brain can override your physical limits if you’re not careful.

Studying the stomach

The researchers recruited 62 obese people who were otherwise healthy. (Fifty-seven were women.) The researchers determined obesity as having a body mass index (BMI is a combined measurement of your height and weight)of over 30; that’s the same as the Centers for Disease Control and Prevention’s BMI scale. The participants didn’t have eating disorders, alcohol problems, or mood disorders like anxiety or depression.

First, participants drank a nutritional supplement called Ensure so researchers could measure the amount of food volume it took each person to feel full. They rated their fullness levels every five minutes, and when they hit “maximum or unbearable,” they stopped drinking.

Now the researchers knew roughly the stomach volume for each participant. Four hours later, the volunteers were offered a buffet of vegetable lasagna, vanilla pudding, and skim milk, and they had 30 minutes to eat as much as they wanted. The scientists kept track of the amount each person ate.

The reasons we overeat

People with larger stomachs could consume up to 30 percent more calories, explains Michael Camilleri, MD, study co-author and consultant in the Division of Gastroenterology and Hepatology in the Department of Internal Medicine at the Mayo Clinic in Rochester, Minnesota. He notes that on average, stomachs enlarged to about three times their fasting size after a meal. Unfortunately, the link between feeling full on the nutritional drink didn’t line up with feeling full at the buffet; the results showed the volunteers could push past their stomach volume when eating real food.

Anyone who has sat down to a Thanksgiving spread knows this to be true: Eagerness to eat can lead you to overdo it—and your stomach size won’t necessarily slow you down. There’s another factor at work, says Dr. Camilleri: A process called gastric emptying rate, which is how fast food leaves the stomach. “It’s estimated that about one in every four people with obesity has fast gastric emptying,” says Dr. Camilleri. In short, the stomach empties food rapidly and then sends a signal that you’re hungry again.

For the study, Dr. Camilleri also tracked gastric emptying and, sure enough, a quick exit could also lead to higher consumption. The volume of your stomach as well as how fast it empties “both impact the amount people eat to feel comfortable or not to feel hungry,” explains Dr. Camilleri.

Aerial View Of Salad And FriesHinterhaus Productions/Getty Images

Carbs didn’t help

There still exists the “perception that non-fat calories [like from carbohydrates] don’t cause overall weight gain,” says Dr. Camilleri. But in the study, eating more carbs typically went hand in hand with having a bigger meal. Eating more fat and protein didn’t have that connection.

What this means for weight loss

The biggest lesson is that the size of your stomach and your desires combine to trigger overeating. You can combat this by imposing limits on yourself. For example, when you’re faced with a buffet, fill a plate with some prime choices—but don’t let yourself go back for seconds. Another option is to remove temptation altogether by not bringing dishes to the table: Instead, serve yourself up in the kitchen, eat at the dinner table, and only return to the kitchen to clean up and stash the leftovers.

In addition to gaining a better understanding of how the body processes fullness, says Dr. Camilleri, his research may also lead to the development of a weight-loss treatment that limits stomach volume or slows gastric emptying. There are already some medications that do this. One, like Liraglutide, slows the rate at which food leaves the stomach, he says. That can help people feel fuller, longer. Indeed a 2015 study in JAMA found that people who were overweight and obese with type 2 diabetes who took 3 milligrams of liraglutide daily lost weight over about a year period, compared to a placebo group. One-quarter of those patients lost more than 10 percent of their body weight, compared to less than 7 percent of patients in the placebo group. Next up, Dr. Camilleri plans to pursue the research looking at people in other weight categories.