Chewing Evidence Isn't Perfect. A Fact-Check of the 3 Biases and Scientific Limitations in Existing 'Chew Well Research'

“People who chew well are less likely to gain weight.” “The higher the number of chews, the higher the cognitive function.” Countless research papers showing these conclusions exist around the world. However, when those with scientific literacy look at this data, they must always cast a doubtful eye (critical appraisal): “Was this conclusion really derived through a correct process?”

By the nature of measuring an extremely daily human behavior, chewing research tends to encompass several unconquerable structural bugs (biases and confounding factors). To warn against the excessive expectation that “chewing solves everything,” this article explains three representative limitations (vulnerabilities) inherent in current chewing evidence.

Limitation 1: The Trap of Self-Reporting Bias

“How much time do you usually spend on a meal?” “How many times do you chew per bite?” In large-scale epidemiological surveys (e.g., cohort studies targeting tens of thousands of people), the vast majority of data regarding chewing is collected through such handwritten questionnaires (self-reporting) (parts of E05 also fall under this).

Here, a despairing amount of noise is mixed in.

• Because humans unconsciously try to make themselves look good (or try to lean towards the “correct” answer), the number of people who self-report “eating fast” is extremely smaller than the actual percentage.
• Moreover, since there is no human being who eats while accurately counting the number of chews, the reported data of “20 minutes per meal” itself contains a fatal measurement error, being nothing more than a completely unreliable sensation/memory value.

Limitation 2: The Possibility of “Reverse Causality”

Against the conclusion of papers stating that “chewing well (A)” brings about “health/weight loss (B),” the hypothesis, “Isn’t it actually the reverse?” always lingers.

In other words, the problem (the wall of external validity) is that it might just be: Not “I became healthy because I chew well,” but “Precisely because I already have high health consciousness, no cavities, and high meal quality (being B), I have the leeway to slowly chew and eat hard things as a result (becoming A).”

• It is extremely difficult to statistically and completely eliminate these “confounding factors (subjects’ income, knowledge level, exercise habits, etc.).” To purely isolate the effect of chewing alone, a Randomized Controlled Trial (RCT) in a sterile state where lifestyle habits are completely controlled is necessary, but it is ethically and physically impossible to forcibly manipulate human eating speed over a long period (the limitation of E12).

Limitation 3: The Disconnect Between the Laboratory Environment and Real Society

When trying to confirm chewing effects through an RCT (Randomized Controlled Trial), it is generally conducted in a controlled laboratory environment. When measured under strict conditions like “Yes, please chew this gum here for 20 minutes to the rhythm of a metronome,” meaningful data (increased blood flow and GLP-1 secretion) is certainly obtained (elucidation of mechanisms related to E06).

However, there is no guarantee that the “strongest data (internal validity)” hammered out in this laboratory will apply directly to our chaotic daily lives (external validity).

• In the real world, we wash down our meals to a random rhythm while looking at our smartphones, talking with colleagues, or feeling stressed. There is a sufficient possibility that the “ideal effects produced in the lab” will not manifest at all during a corporate slave lunch full of distracting thoughts.

How Do We Deal With the Risks?

It is premature to conclude that “the chewing effect is meaningless because it’s not perfect.” This is because, even if there are doubts about self-reporting noise or reverse causality, it is an unshakable physiological fact that “dependence on soft diets without chewing” causes fatal damage to metabolism and the autonomic nervous system (the evils of fast eating).

By knowing the limitations, we can stop believing in the magic that “you’ll lose weight if you chew.” Instead, it becomes possible to coolly and strategically utilize chewing as “one of the handiest, zero-side-effect early switches among numerous metabolic hacking tools.”