You’ve probably heard that “you are what you eat.” But here’s a truth that’s even more unsettling: your body responds differently to the same food depending on what you believe about it.
Not in some vague, feel-good way. In a measurable, physiological, hormone-changing way.
If that sounds impossible, consider this: researchers gave people the exact same milkshake twice and measured their hunger hormones. When people thought they were drinking an indulgent, high-calorie shake, their bodies responded as if they’d consumed three times more calories than when they believed they were drinking a sensible, low-calorie shake.
Same shake. Different beliefs. Completely different physiological responses.
This is the power of mindset on food, and it changes everything we thought we knew about nutrition.
The Milkshake Study That Changed Everything
Dr. Alia Crum, now a professor at Stanford University, conducted this groundbreaking study as a graduate student at Yale. The research question was deceptively simple: Do our beliefs about what we’re eating change our body’s physiological response to that food, even when the objective nutrients remain constant?
The study brought participants into the lab under the impression that they were testing different milkshakes with vastly different nutrient profiles designed for different metabolic needs. Each person consumed two different milkshakes a week apart.
At one visit, participants were told they were drinking a high-fat, high-calorie indulgent shake: 620 calories, loaded with fat and sugar. At the other visit, they were told it was a low-fat, low-calorie sensible “diet” shake.
Here’s the kicker: it was the exact same shake both times. A moderate 300-calorie shake, right in the middle of the two descriptions.
What the researchers were really measuring was ghrelin, often called “the hunger hormone.” Ghrelin rises when you need food and drops when you’ve eaten, signaling to your brain that you’re satisfied and revving up metabolism to burn what you just consumed.
The results were stunning.
Your Beliefs Change Your Hormones
When people thought they were drinking the indulgent, high-calorie shake, their ghrelin levels dropped at a threefold rate compared to when they thought they were drinking the sensible shake.
Read that again: a threefold difference.
Their bodies responded as if they had consumed significantly more food, even though the actual calories and nutrients were identical. This wasn’t placebo; this was a direct belief effect where thoughts about food created measurable changes in hunger hormones, insulin response, and blood glucose levels.
Dr. Crum explains: “This is a belief effect where the belief and the subjective thoughts about what a given food will do has a direct impact on a physiological measure like blood sugar and blood glucose.”
The Counterintuitive Finding
Here’s where it gets even more interesting, and potentially more practical.
Dr. Crum went into the study thinking the “healthier” mindset would be better: believing you’re eating something healthy should make you healthier, right? That’s what most of us would assume.
But the results showed the exact opposite.
When participants thought they were eating sensibly, their bodies left them still feeling physiologically hungry, not satiated. This could correspond to slower metabolism and less satisfaction from meals.
The practical takeaway? If you’re interested in maintaining or losing weight, the best mindset to be in when eating is that you’re having enough food, that you’re satisfied, that you’re eating something indulgent and fulfilling.
Paradoxically, believing you’re eating “diet food” may actually work against your goals by leaving you physiologically hungry and potentially slowing your metabolism.
This Goes Beyond Just One Study
Andrew Huberman, professor of neurobiology at Stanford, discusses this research in the context of brain health and nutrition: “The physiological response, the insulin response, the blood glucose response, and the subjective measures of whether or not people enjoyed something or not, were heavily influenced by what they were told were in these milkshakes.”
He emphasizes that this is a belief effect, distinct from placebo. A placebo effect occurs when a control condition influences outcomes to some degree like the experimental condition. A belief effect is when your beliefs directly change physiological measures, regardless of objective inputs.
This phenomenon has profound implications for why different diets work for different people. If you’re strictly plant-based, omnivore, carnivore, doing intermittent fasting, or following any other eating pattern, mindset effects are likely involved in your results.
As Dr. Crum points out: “It does matter what it is and it matters what you think about that diet and what others around you and in our culture think about that diet because those social contexts inform our mindsets. Our mindsets interact with our physiology in ways that produce outcomes that are really important.”
The Combined Product of Action and Belief
The key insight here isn’t that nutrition doesn’t matter. It’s that the total effect of anything is a combined product of what you’re doing and what you think about what you’re doing.
This explains a lot:
- Why people in different diet camps all seem to experience genuine benefits from their chosen approach
- Why some people thrive on diets that make others miserable
- Why believing in your nutrition plan may be just as important as the plan itself
- Why stress and anxiety about “not eating right” might actually undermine your health
Dr. Crum emphasizes: “Let’s not get dualistic and say it’s either all in the mind or not in the mind. Let’s also not be unnecessarily combative and say it should be all plant-based or keto or whatever. It’s all of those things are a combined product of what you’re actually doing and what you’re thinking about.”
Practical Applications
So what do you do with this information?
1. Stop treating food as the enemy
If you’re constantly thinking about your meals as “just diet food” or “healthy but unsatisfying,” your body may be responding accordingly. Ghrelin stays elevated. You remain hungry. Your metabolism may slow.
2. Cultivate satisfaction, not restriction
When eating, adopt the mindset that you’re having enough food, that it’s nourishing and satisfying, that you’re taking care of your body’s needs. This isn’t about lying to yourself or eating junk; it’s about framing healthy food as fulfilling rather than limiting.
3. Believe in your approach
Whatever eating pattern you choose, commit to it mentally as well as physically. Skepticism and doubt may actually undermine the physiological benefits you’d otherwise experience.
4. Watch out for nocebo effects
The flip side of positive belief effects is nocebo effects: negative beliefs causing negative consequences. If you think you “should” be eating a certain way but don’t believe in it or resent it, the stress and anxiety associated with that might have adverse effects.
5. Respect individual differences
This research helps explain why nutrition is so personal. The mindset you bring to eating matters enormously, and that mindset is shaped by your culture, community, beliefs, and experiences. There’s room for multiple approaches to work.
The Mind-Body Connection Is Real
We’ve spent decades optimizing macros, timing nutrients, and searching for the perfect diet. And while nutrition science matters, we’ve been missing a crucial variable: what you believe about your food actively changes how your body processes it.
Your mindset about eating isn’t just motivation or willpower. It’s a biological variable that directly influences hunger hormones, insulin response, blood glucose, metabolism, and satiety.
The same food can have different effects depending on what you think about it.
So before you overhaul your entire diet or jump to the next nutrition trend, ask yourself: Do you believe in what you’re eating? Do you approach meals with satisfaction or stress? Do you view your food as nourishing or limiting?
Your answers to those questions might matter just as much as what’s on your plate.
References
- Crum, Dr. A. Featured on Huberman Lab: “Essentials: Science of Mindsets for Health & Performance”
- Huberman, Dr. A. “Essentials: Food & Supplements for Brain Health & Cognitive Performance”
- Crum, A. J., Corbin, W. R., Brownell, K. D., & Salovey, P. (2011). Mind over milkshakes: Mindsets, not just nutrients, determine ghrelin response. Health Psychology, 30(4), 424-429.
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