Japanese researchers followed 1,083 adults for five years, splitting them into three categories based on how quickly they ate: slow, normal, and fast. They also answered a questionnaire at the beginning of the study, sharing their diets, physical activity, and medical history. In the beginning, none of the volunteers had metabolic syndrome—meaning at least three risk factors including abdominal obesity, low “good” HDL cholesterol, high triglycerides, high blood pressure, and high blood sugar—which can lead to health problems like heart conditions and diabetes. Watch out for these 7 other signs of metabolic syndrome.
When the participants reported back five years later, 84 had been diagnosed with metabolic syndrome—and their eating speed was a major predictor, according to results in the journal Circulation. The fast eaters were 89 percent more likely to have metabolic syndrome than slow and normal eaters. Just 2.3 percent of slow eaters received the diagnosis, compared to 11.6 percent of fast eaters.
But that’s not all. Fast eaters also saw more weight gain, larger waistlines, and higher blood sugar levels than slower munchers. The researchers say gobbling down your meal makes it easier to blow past fullness before your body has a chance to signal you to stop. “When people eat fast they tend not to feel full and are more likely to overeat,” said Takayuki Yamaji, MD, study author and cardiologist at Hiroshima University in Japan in a statement. “Eating fast causes bigger glucose fluctuation, which can lead to insulin resistance.” (Check out this other surprising eating habit that could make you gain weight.)
Previous research backs up the weight benefits of slow eating, too. One study of New Zealand women found fast eaters have higher body-mass indexes, and a Chinese study found that both healthy and obese men ate less when told to chew 40 times instead of 15 times before swallowing. Preliminary research even suggests chewing your food longer could burn more calories—up to about 1,000 extra every month.
Not that fast eating is the only factor making you put on pounds. Don’t miss these other 11 sneaky causes of weight gain that don’t have to do with food or exercise.