How Food Choices Shape Memory, Cognition & Cravings | Dr. Scott Kanoski

Episode Overview

• Host and Guest Context: Stanford Professor of Neurobiology and Ophthalmology Dr. Andrew Huberman interviews Dr. Scott Kanoski, Professor of Human and Evolutionary Biology and Neurobiology at the University of Southern California (USC). Huberman notes the podcast is separate from his Stanford roles and discloses sponsors Our Place (Titanium Always Pan Pro), Helix Sleep (Dusk mattress paired with Truemed for HSA/FSA), AG1 (AG1 Pro containing 5g creatine monohydrate, calcium HMB, and zinc carnosine; Huberman has taken AG1 for nearly 14 years), Element (LMNT), and Function Health (which he also uses alongside Our Place, Helix Sleep, and Element). Kanoski notes his research is supported by the NIH funding model and taxpayer dollars, and mentions early-career brushes with the sugar lobby regarding public-facing statements on his sugar research.
• Gut-Brain Signaling and GLP-1 Pharmacology: The conversation explores how physiological gut hormones like GLP-1 communicate with the brain via the vagus nerve to regulate blood glucose and satiation, contrasting natural signaling with super-physiological GLP-1 weight-loss drugs and their side effects, discontinuation rates, and brain-penetration questions.
• Memory as a Master Regulator of Appetite: The episode reveals how the hippocampus—traditionally viewed purely as a memory center—is essential for interpreting internal hunger and fullness cues (interoception) and how visual memories of meal size override actual stomach fullness hours after eating.
• Dietary Impacts on Brain Health and the Microbiome: Kanoski details preclinical and human evidence showing how Western diets, adolescent sugar consumption, artificial sweeteners, and heat-processed foods (Advanced Glycation End-products) alter the gut microbiome and impair hippocampal memory—often persisting into adulthood.
• Reward Pathways and Neuro-Modulation: The discussion concludes by examining how dopamine, acetylcholine, and oxytocin dynamically regulate food cravings, nutrient-driven memory encoding, and socially facilitated eating, while highlighting how exercise and vagus nerve stimulation can rescue diet-induced cognitive deficits.

Key Concepts

• Natural vs. Pharmacological GLP-1 Signaling: Natural GLP-1 (glucagon-like peptide-1) is an incretin hormone secreted from the L-cells of the distal intestines slightly before and during a meal, as well as in the brainstem (nucleus tractus solitarius). While peripheral and central GLP-1 systems both suppress appetite, they appear to operate independently. GLP-1 regulates blood glucose by stimulating insulin secretion when blood glucose is high, which is why GLP-1 drugs were first applied to diabetes rather than obesity. Physiological GLP-1 acts via a paracrine mechanism, binding immediately to receptors on adjacent gastrointestinal vagus nerve terminals. In preclinical rodent models, Wolfgang Langhans and colleagues in Zurich showed that a selective sensory lesion of the GI vagus nerve prevents injected native (short half-life) GLP-1 from reducing food intake, and knocking down vagal GLP-1 receptors via short hairpin RNA interference results in animals eating larger meals.
• GLP-1 Drug Mechanics, Penetration, and Limitations: Drugs like Ozempic and Wegovy raise GLP-1 to super-physiological levels—roughly 1,000-fold higher than natural levels. GLP-1 receptors are densely expressed throughout the brain, including the hippocampus and reward circuitry (mesostriatal pathway, midbrain VTA, striatum, nucleus accumbens), suggesting potential applications for dementia and substance abuse disorders (unlike 1990s Fen-Phen/fenfluramine, which acted as a sympathomimetic/stimulant and was discontinued due to cardiovascular outcomes). However, Kanoski notes "the jury's still out" on whether newer GLP-1 drugs cross the blood-brain barrier. While preclinical rodent evidence on first-generation GLP-1 drugs (from 2005–2012) suggested they entered the brain to suppress food intake, studies tagging newer GLP-1 peptides with fluorescent molecules show them clumping in circumventricular organs (which lack a blood-brain barrier). Elizabeth Rhea, Bill Banks, and colleagues at the University of Washington use Carbon-14 radiolabeled peptides to study this; early-generation drugs readily enter the brain, while newer ones are less clear or take longer. Furthermore, clinical trials (which typically last 1 to 2 years and embed nutritional and physical activity guidelines) show the most common side effects are nausea and emesis (vomiting). A majority of people discontinue treatment within 2 years due to side effects or lean mass loss (especially in elderly populations). Kanoski also warns there is no clinical data on microdosing GLP-1s (only anecdotal reports vs. strong placebo effects), no data on lean, non-diabetic individuals taking them, and while patients report reduced "food noise" (which neither Huberman nor Kanoski personally experience), it is unknown if this occurs via central brain receptors or gut-vagus satiation mechanisms.
• Artificial Sweeteners and the Cephalic Phase Response: Sweet taste triggers a "cephalic phase response," releasing insulin before nutrients enter the GI tract to prepare for blood glucose changes. Preclinical animal models show that uncoupling sweet taste from caloric consequences via artificial sweeteners perturbs appetite and glucose regulation. In Kanoski's lab, juvenile/adolescent rodents given daily voluntary access to Stevia, Ace-K, or Saccharin within FDA acceptable daily intake levels (equivalent to about 6 sweetened beverages a day) developed adult hippocampal-dependent memory impairments, altered tongue sweet taste receptor expression, and larger insulin spikes when glucose was infused bypassing the mouth—even after stopping the sweeteners and eating healthy rodent chow (which is 10% to 15% calories from fat with complex carbohydrates) and water. However, Kanoski hedges strongly against applying this to humans, noting human randomized clinical trials on artificial sweeteners are "all over the place," humans are notoriously inaccurate at self-reporting diet in nutrition studies, and both he (drinking Coke Zero) and Huberman (drinking Yerba Mate with stevia) consume low-calorie sweeteners during the episode.
• Episodic Memory and Interoceptive Agnosia: The hippocampus is required to remember eating and to interpret physical fullness signals. In a human study by Jeff Brunstrom and colleagues using a peristaltic pump attached to a tomato soup bowl, participants saw 300 mL or 500 mL while actually consuming 500 mL or 300 mL; immediate hunger matched actual consumption, but a couple of hours later, hunger ratings flipped to match what they remembered seeing. Similarly, Paul Rozin and others studied densely amnesic humans with bilateral medial temporal lobe/hippocampal damage (10 to 40 second memory span) who would eat up to three full meals in a row and still rate their hunger as a 7 out of 10 on a 0 to 10 scale. In rodent models, normal animals use hunger vs. fullness as an interoceptive cue to predict a foot shock or food pellet, but hippocampal lesions cause "interoceptive agnosia," preventing them from using hunger states to guide behavior—an impairment also induced by high-fat, high-sugar diets.
• Western Diets, Adolescent Sugar, and Heat-Processed Foods (AGEs): Over 60% of US calories come from ultra-processed foods, and over 40% of US adults are obese (up from ~20% in the 1990s). In adult rodents, a "Western diet" (~35% fat, 15% simple sugars) causes hippocampal memory impairments in as little as 1 week. Juvenile/adolescent rodents given ad libitum access to a sugar solution (matching human soft drink calorie percentages) alongside healthy food and water, or fed a "junk food diet" (chocolate peanut butter cups, ruffled potato chips, high-fat/high-sugar chow), develop hippocampal memory deficits that persist into adulthood even after switching to a healthy diet. In an unpublished, non-peer-reviewed rodent preprint from Kanoski's lab testing the NOVA classification of ultra-processed foods, researchers baked otherwise healthy rodent food for 1 hour at high heat to induce the Maillard reaction and create Advanced Glycation End-products (AGEs), which bind to RAGE receptors; juvenile rodents fed this AGE-enriched diet developed adult memory impairments. Kanoski's lab tests memory using a table-sized Barnes-style maze and novel object-in-location recognition arenas (where diet-impaired animals perform at chance levels), avoiding the Morris water maze because swimming is stressful and physically demanding for rats. In humans, Dick Stevenson and colleagues found correlations between habitual sugar and saturated fatty acid intake and poorer hippocampal memory in young adults (undergraduates). Prospective human studies also link midlife dietary patterns and metabolic status (like visceral adiposity) to later dementia risk, and Western diets accelerate pathology and symptom onset in transgenic Alzheimer's rodents. However, Kanoski emphasizes that human midlife diet-dementia links are correlational, not a direct 1-to-1 causal line, and switching diets after symptoms arise is unlikely to be a cure compared to lifelong healthy eating (whereas Huberman notes UC Santa Barbara research showing omega-3 supplementation during pregnancy positively relates to offspring brain size and function).
• The Gut-Vagus-Hippocampus Acetylcholine Pathway: Kanoski's lab mapped a 3-tier pathway where the GI vagus nerve signals to the brainstem, which projects to the medial septum, where acetylcholine-producing neurons innervate the hippocampus. Lesioning the GI vagus nerve in rodents impairs hippocampal memory. In humans, a small retrospective study of Taiwanese medical records found patients who received a truncal vagotomy in the 1980s/1990s for stomach ulcers had an increased risk of developing dementia later in life (which Kanoski hopes to investigate further using the Swedish National Registry). Using fiber photometry in awake rodents, Kanoski's lab showed that hippocampal acetylcholine ramps up in a staircase effect while an animal actively chews and swallows food, ramping down during pauses and settling at a higher postprandial baseline. This occurs with both healthy and high-fat/high-sugar foods, but does not occur with non-nutritive taste alone (such as consuming stevia). Furthermore, Kanoski's lab is testing Vagus Nerve Stimulation (VNS) devices sutured to the stomachs of transgenic Alzheimer's rats (which develop age-dependent hippocampal amyloid and tau pathology); the devices stimulate the nerve only during natural stomach distention/contraction while eating and have already been shown to rescue diet-induced memory impairments.
• Microbiome Plasticity in Diet-Induced Memory Deficits: Since the Human Microbiome Project ended around 2012, PubMed hits for the microbiome have grown from ~7,000 ten years ago to ~250,000 today. While FDA-approved fecal transplants successfully cure violent C. diff (Clostridioides difficile) infections after antibiotics, Kanoski cautions we are "not even close" to labeling specific bacteria as universally good or bad because effects are context-dependent. In his lab's early-life sugar rat model, the gut bacterium Parabacteroides increased roughly 2-fold and negatively correlated with memory; treating healthy, non-sugar-fed rats with antibiotics and enriching Parabacteroides roughly 8-fold replicated and worsened hippocampal memory deficits. Conversely, in the unpublished heat-treated (AGE-enriched) diet preprint, the lactic-acid-producing bacterium Lactococcus was completely eliminated by the diet, and re-introducing/enriching Lactococcus rescued the memory impairments.
• Dopamine State-Dependency and Oxytocin's Dual Role: The mesostriatal dopamine pathway (midbrain VTA to nucleus accumbens) responds to palatable foods (liquid sucrose, high-fat/high-sugar), but is also state-dependent: bland food triggers dopamine in food-restricted animals, water in water-restricted animals, and sodium in sodium-depleted animals. It is also plastic: in conditioned taste aversion, pairing sucrose with an illness-inducing injection eliminates the dopamine response to sucrose and its cues. Regarding "food addiction," Kanoski declines to take a firm side, noting that while eating behaviors can fit DSM criteria, food is required daily for survival unlike drugs of abuse. Meanwhile, oxytocin is produced in the PVH of the hypothalamus and projects to the brainstem and throughout the brain. While Harvey Grill and others showed brainstem oxytocin reduces food intake by increasing satiation and reducing meal size, Kanoski's lab found that "social facilitation of eating" (where humans and rodents eat more with familiar peers than alone or with strangers) requires oxytocin signaling in the hippocampus; genetically turning down hippocampal oxytocin receptors eliminates this social overeating.

Quotes

• At 0:00:20 - "With this model, the animals show hippocampal-dependent memory deficits when they're older, and these seem to persist later into life even though they're not consuming the sugar anymore." - Explaining how adolescent exposure to liquid sugar causes long-term cognitive deficits in rodents even after transitioning to a healthy adult diet.
• At 0:00:44 - "So we give them chocolate peanut butter cups, ruffled potato chips, rodent high-fat, high-sugar diet. They show these memory impairments that last even after you switch them to a healthy diet." - Describing the "junk food" cafeteria diet model in juvenile rodents and its lasting impact on adult hippocampal memory.
• At 0:03:32 - "In its natural form, it's an incretin hormone, so it's secreted from the distal intestines around food ingestion, so there's a little bit of secretion before the meal actually starts, then there's additional secretion during the meal, and this gets into circulation." - Defining the physiological baseline and timing of natural GLP-1 release in the gut.
• At 0:05:30 - "There are side effects, nausea and emesis—emesis being vomiting—the most common side effects, and this can lead to discontinuation in a lot of people." - Highlighting the primary gastrointestinal side effects driving patients to stop taking super-physiological GLP-1 medications.
• At 0:07:48 - "The receptor for GLP-1 is not exclusively expressed in regions of the brain that control appetite and food intake and glucose regulation; they're pretty densely expressed throughout the brain." - Explaining why GLP-1 drugs are being investigated for broader neurological applications like substance abuse and dementia.
• At 0:14:51 - "This paracrine mechanism is where the GLP-1 is released from these L-cells in the intestines and immediately act on nearby receptors that are expressed on the vagus nerve." - Clarifying how natural gut GLP-1 communicates satiation to the brainstem locally rather than relying on bloodstream circulation.
• At 0:21:11 - "Kind of like you're tricking the wisdom of the body, right? So sweet taste means calories are coming—oh wait, but now it doesn't." - Describing how non-nutritive sweeteners disrupt the evolutionary cephalic phase response linking sweet taste on the tongue to caloric intake.
• At 0:28:03 - "So in general, the memory of recent eating will contribute to eating less at the subsequent eating occasion." - Summarizing human research showing that episodic memory of a meal actively suppresses subsequent snacking.
• At 0:29:11 - "A couple hours later, that flips, and their hunger ratings were more driven by what they saw—what they think they consumed—versus what they actually consumed." - Detailing Jeff Brunstrom's peristaltic soup bowl study, proving visual memory of portion size overrides gastric physiology hours after a meal.
• At 0:31:04 - "So we think that these systems that are responding to nutrients when we eat are actually promoting memory function, potentially this is a system that evolved because of how important it would have been to remember these eating occasions." - Offering an evolutionary framework for why nutrient detection in the gut directly stimulates memory encoding in the hippocampus.
• At 0:33:36 - "The best diet is one that you can stick to, and that's going to be a different approach for different people." - Paraphrasing obesity researcher George Bray on the necessity of personalized adherence over rigid dietary dogma.
• At 0:35:04 - "So the hippocampus is somewhat of a canary in the coal mine." - Emphasizing the extreme vulnerability of the hippocampus to metabolic perturbations, Western diets, and inflammatory insults.
• At 0:48:33 - "There is some evidence that exercise can reverse those memory deficits, and in part that's happening through changes in the brain." - Pointing out that physical activity can rescue cognitive impairments induced by a high-fat, high-sugar Western diet.
• At 0:51:23 - "If you lesion the vagus nerve as it's coming out of the gut, the gastrointestinal-innervating components of the nerve, animals show hippocampal-dependent memory impairments." - Demonstrating that intact gut-to-brain vagal signaling is required for normal memory performance, independent of appetite control.
• At 1:03:30 - "Over 60% of calories that—not maybe not you or I—but like many people consume come from ultra-processed foods in the US." - Framing the scale of ultra-processed food consumption in the modern American diet.
• At 1:07:45 - "A majority will discontinue treatment within two years of starting." - Noting the high drop-off rate for patients prescribed GLP-1 weight-loss drugs due to side effects and lean mass loss.
• At 1:18:43 - "If you track the acetylcholine release into the hippocampus when the animals are actively eating—so they're holding food, they're chewing it, they're swallowing—the acetylcholine levels are ramping up when that's happening." - Explaining the real-time neurochemical mechanism by which the act of eating nutritive food drives memory encoding.
• At 1:20:35 - "We don't see this with taste alone. So if the animals consume stevia, a non-nutritive sweetener, we don't see the acetylcholine release patterns in the hippocampus." - Contrasting caloric intake with artificial sweeteners, which fail to trigger the gut-vagus-hippocampal acetylcholine staircase effect.
• At 1:23:38 - "So of course they're getting this gut feedback to the brain, they're probably even feeling full, but they don't know how to interpret that signal; the hippocampus is needed to understand what that signal means." - Explaining why amnesic patients with hippocampal damage experience interoceptive agnosia and will eat three full meals in a row.
• At 1:58:24 - "We found that that phenomenon requires oxytocin signaling in the hippocampus, so if you genetically turn down the signal, the animals don't show that effect." - Revealing the specific neural mechanism behind the "social facilitation of eating," where dining with familiar peers drives increased food consumption.

Takeaways

• Eat Mindfully to Strengthen Meal Memories: Because recalling a recent meal suppresses subsequent snacking—as demonstrated by Suzanne Higgs and colleagues, where participants primed to remember their pizza lunch ate fewer cookies ("biscuits") later—avoid distracted eating and consciously attend to your meal to encode a strong episodic memory.
• Leverage Visual Portion Cues for Long-Term Satiety: Since hunger hours after eating is heavily driven by how much food you remember seeing rather than actual caloric volume, use visual plating strategies that register as a complete, substantial meal to prevent premature return of hunger.
• Protect the Developing Adolescent Brain from Liquid Sugar and Junk Food: Limit habitual consumption of sugar-sweetened beverages and ultra-processed junk foods during childhood and adolescence, as preclinical models show early-life exposure causes persistent hippocampal memory deficits and microbiome alterations in adulthood even after switching to a healthy diet.
• Minimize High-Heat Charred and Ultra-Processed Foods: Reduce intake of heavily browned, baked, or fried ultra-processed foods rich in Advanced Glycation End-products (AGEs from the Maillard reaction), which preclinical data suggests can deplete beneficial lactic-acid bacteria (Lactococcus) and impair memory independently of sugar or fat content.
• Use Physical Exercise to Buffer and Reverse Dietary Brain Deficits: Incorporate regular aerobic and physical exercise into your routine, which animal studies show can reverse hippocampal memory impairments caused by consuming a high-fat, high-sugar Western diet.
• Pair GLP-1 Medications with Resistance Training and Nutrition: If taking a GLP-1 agonist under medical supervision, actively follow resistance exercise and nutritional protocols (as embedded in clinical trials) to mitigate lean muscle mass loss, and avoid unstudied practices like "microdosing" or using these drugs if you are already lean and non-diabetic.
• Recalibrate Your Palate Away from Hyper-Palatable Foods: Because the mesostriatal dopamine system is highly plastic and state-dependent, temporarily stepping away from ultra-processed high-fat/high-sugar foods allows your reward circuitry to reset so that whole, minimally processed foods become naturally rewarding.
• Account for Social Overeating Around Familiar Peers: Recognize that dining with friends and family triggers hippocampal oxytocin signaling ("social facilitation of eating") that naturally increases meal size; plan portion sizes in advance during social gatherings if managing caloric intake.
• Consume Whole Nutritive Foods to Support Memory Encoding: Rely on whole, caloric nutrients rather than non-nutritive sweeteners to properly engage the gut-vagus-septal pathway that drives post-meal acetylcholine release in the hippocampus.
• Moderate Artificial Sweetener Intake During Youth: While human clinical data on low-calorie sweeteners remains mixed, exercise caution with heavy daily consumption (e.g., multiple diet sodas or sweetened beverages daily) in juveniles, given animal evidence of lasting shifts in glucose regulation, tongue taste receptors, and memory.
• Prioritize Midlife Metabolic Health for Dementia Prevention: Because prospective human studies link midlife visceral adiposity and dietary patterns to late-life dementia risk—and changing diets after cognitive symptoms appear is unlikely to reverse pathology—adopt a low-sugar, low-saturated-fat diet early in adulthood.
• Choose a Sustainable Dietary Pattern: In alignment with obesity researcher George Bray's principle that "the best diet is one that you can stick to," select a nutritious eating framework that fits your personal preferences and lifestyle for lifelong adherence rather than cycling through extreme short-term restriction.