Blood sugar levels may influence food choice more than weight

Scientists suggest that glycemic control measures may influence food choice and eating behaviors, not body weight, as is often studied. The Virginia Tech, US, team used flavor-nutrient learning — “training” participants to associate a specific flavor with calories by pairing an unknown or unliked flavor in a drink with sugar. 

Flavor-nutrient learning influences eating habits and may impact body weight, as it teaches how people prefer certain foods based on how they make them feel. 

When the researchers removed sugar from test beverages, some participants preferred the flavor paired with calories. However, the findings were not uniform — participants with higher fasting glucose and blood glucose levels over time (A1C) were less likely to prefer the flavors paired with nutrients. 

“One of the most interesting findings was that measures of body weight status — body mass index (BMI), waist-to-hip ratio, and waist circumference — were not related to individual responses,” says the study’s first author, Mary Elizabeth Baugh, a research scientist at the university’s Fralin Biomedical Research Institute.

“We need more data, but this points to potentially impaired learning based on post-ingestive signals. With higher values of glycemic control, even within the normal range, there could potentially be some disruption in gut-brain signaling.”

Flavor-nutrient learning

Although research in animal models points to the importance of signals from the gut to the brain after eating, scientists argue that this is difficult to show in people. Eating habits and food preferences vary widely, while testing conditions in animal studies can be strictly controlled. 

The study, published in Physiology & Behavior, included 26 participants from Southwest Virginia. The paper pooled data from two preliminary studies with similar randomized crossover designs. 

Due to post-ingestive mechanisms, participants still preferred the flavor paired with calories even when sugar was removed.The team introduced participants to ten atypical flavors: acerola, bilberry, horchata, lulo, yuzu, papaya, chamomile, aloe vera, mamey, and maqui berry. 

“The best practice is to take something strange, because we want new learning to happen,” explains lead researcher Alexandra DiFeliceantonio, faculty member at the institute and interim co-director of its Center for Health Behaviors Research. 

After participants rated how familiar these flavors were and how much they liked them, the researchers proceeded with two flavors that were less familiar and liked by individual participants. 

The team matched flavored drinks for sweetness, with one containing sugar and the other an artificial sweetener — one drink provided calories and the other didn’t. The participants consumed the beverages at home at specified times over several weeks. 

Next, the researchers ensured both drinks used artificial sweeteners, so calories would not confound results during the testing session. 

Participants still preferred the flavor paired with calories even when sugar was removed. “And that’s because of post-ingestive mechanisms, not anything related to sweetness,” says Baugh. 

The researchers noted that their findings stood out because none of the participants had been diagnosed with diabetes or prediabetes, and they represented a wide range of BMI categories. 

Gut-to-brain communication

Baugh explains that signals from the gut to the brain after eating are necessary, beyond oral taste signals, to guide food preference. 

The study’s findings can also affect people with healthy BMI and A1C ranges, as fluctuations in blood glucose influence what they eat.“We wanted to know whether the gut-to-brain system for relaying information about nutrient learning might be different for people who have obesity and those with differences in glycemic control,” adds DiFeliceantonio. “If it’s different, we should use different targeted strategies to help them change their diet.”

She highlights that post-ingestive signals are less well studied — “our gut talking to our brain, teaching us what to eat.” 

DiFeliceantonio underscores that the study’s findings don’t only affect people who meet the criteria for overweight and obesity. “Even if you are a person with a healthy range BMI and a healthy range A1C, fluctuations in your blood glucose are still influencing what you eat in a way that you might not be aware of.”

Meanwhile, Baugh adds that more research is needed as the study was small. She is recruiting participants with a broader range of glycemic control and body weights to inform public health better. 

“Ultimately, understanding the mechanisms that influence food choice and eating behaviors can be impactful in developing different pharmacological or behavioral strategies for obesity treatment — and even prevention,” she concludes. 

In related research, psychologists have pinpointed overactive food-seeking neurons rather than an overactive appetite as a potential cause behind post-meal snack cravings.