Burn Fat Just by 'Chewing'? The Mechanism Where Mastication Stimulates the Sympathetic Nervous System and Forcibly Activates Heat Production (DIT) in Brown Adipocytes

“The basis of dieting is to increase calories burned more than calories consumed.” In this simple arithmetic, many people focus only on “how to reduce calorie intake (dietary restriction)” or “how to burn calories through exercise.” However, within the energy consumed just by being alive, there is a hidden parameter that can be dramatically increased or decreased simply by “how we eat.” That is “Diet-Induced Thermogenesis (DIT),” and its ignition switch is “chewing.”

In this article, we unravel the neurological process of why simply moving your jaw generates heat from deep within your body and promotes fat burning.

The Ignition Process of the “Sympathetic Nervous System” Starting from Chewing

The act of “chewing” food in the mouth and grinding it three-dimensionally with the back teeth violently stimulates the “trigeminal nerve,” the thickest cranial nerve crawling across the face.

• The physical pressure and rhythmic electrical signals generated by chewing sprint directly from the trigeminal nerve to the brainstem (reticular formation) and hypothalamus (also related to the stimulation of the arousal network in E11).
• This intense input into the brain properly excites the “sympathetic nervous system” within the autonomic nervous system. The sympathetic nervous system typically plays the role of putting the body into a “battle state (energy burning state)” during stress or exercise.

In other words, chewing firmly is an act of issuing an advance command (alert) to the brain: “A large amount of energy is about to enter the body, so burn it as heat to process it.” In a state of swallowing without chewing (fast eating or liquid diets), this alert is not sounded, so the body does not consume the energy as heat, but instead chooses the path of “storing it as fat (energy-saving mode)” (relationship between obesity and chewing in E06).

Directly Activating “Brown Adipocytes”

Tracing the mechanism even deeper, it is understood that the sympathetic nervous system, excited by chewing, forcibly raises the activity of “Brown Adipose Tissue (BAT)” located in specific parts of the body.

Normally, the fat around our waist is white adipocytes that “store” energy. On the other hand, brown adipocytes are a group of specialized cells with the exact opposite role of “burning fat and turning it into heat (a heater),” existing in small numbers mainly between the shoulder blades and around the neck.

• Recent research (such as the heat production mechanism in E03) shows that noradrenaline secretion from the sympathetic nervous system presses the switch for brown adipocytes, making the mitochondria (UCP1 protein) within the cells run at full capacity to create heat.
• In experiments comparing a “chew well” group and an “eat fast and swallow” group, it has been confirmed that the former clearly has a higher postprandial energy expenditure (DIT) and that the rise in body temperature continues for a longer time.

Daily Chewing Strategy to Create a “Burning Body”

To hack this “heat production (fat burning) system via chewing” to the maximum extent in daily life, the “physical design of each bite” becomes more important than the content of the meal itself.

• Start with the Hardest Item for the “First Bite” of Every Meal: To sound the alert to the brain at the earliest possible stage, start eating with the “ingredient that requires the jaw muscles the most” in that meal, such as root vegetables in a salad, brown rice, or tough meat.
• Do Not “Eat While Doing Something Else” (Synchronizing Vision and Chewing): Unconscious chewing while looking at a smartphone weakens the feedback to the brain. Mindful eating, directing your consciousness to the sensation and rhythm of your jaw “chewing,” improves the quality of the signal to the sympathetic nervous system.

“Chewing” looks like an extremely localized movement taking place inside the mouth, but in reality, it is the “easiest switch” to forcibly reboot the entire body’s energy metabolic engine (brown adipocytes).