The causes of weight gain and obesity are layered and complex, with numerous, interrelated factors playing key roles. A new study linking higher body mass index (BMI) and an aversion to bitter foods has just added another component to the mix: taste.
The study, "Facial Affective Reactions to Bitter-Tasting Foods and Body Mass Index in Adults" [pdf], featured in international research journal Appetite, sought to explain why people who are overweight or at risk of becoming overweight eat differently than thinner people. The researchers hypothesized that people with higher BMI had an aversion to bitter foods and consequently avoided them. Because bitter foods are often fruits and vegetables -- think grapefruit, kale and brussels sprouts -- which are high in dietary fiber and water content and contain no saturated fat, refined carbohydrates or added sugar, the researchers supposed avoiding these foods could affect weight.
Forty participants -- 28 females and 12 males who had no history of eating disorders, aversions, allergies or illnesses -- were divided into two groups: low BMI and high BMI. Everyone tasted two bitter drinks: five milliliters of a grapefruit juice drink and five milliliters of a bitter chocolate drink, both in 10 milliliter plastic cups. Researchers measured participants' subjective reaction, as well as their facial expressions.
For the subjective part, participants filled out a survey detailing their preference and consumption of bitter substances. After they tasted the bitter drinks, they rated the taste on a scale of zero to 100, zero being not at all bitter and 100 being extremely bitter. Researchers also measured facial expressions after participants drank the substances by videotaping them and comparing the degree to which their expression changed from before tasting to afterward.
The results confirmed the researchers' hypothesis, showing that the bitter-tasting drinks "elicited significantly more intense disgust reactions" in participants with high BMI than those with low BMI.
Taste, aversive or otherwise, can only partially explain why people may be overweight or susceptible to becoming so, the study acknowledges. Body mass index is a "complex variable," and a more intense responses to bitter flavors, which can lead to the avoidance of some healthy food like bitter-tasting fruits and vegetables, is just one possible cause.
Almost 70 percent of U.S. adults are overweight, and a third suffer from obesity, which was officially classified as a disease in June 2013. With so many people overweight or obese, researchers stress the urgency of future study on the causes of weight gain, and specifically the effects of an individual's taste for bitter foods.
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