Your Beliefs Can Fool Your Stomach, Research Claims

Your thoughts and emotions can affect your body, even changing certain biological markers. Discover how what you believe about your food can alter some of your biological reactions.
Your Beliefs Can Fool Your Stomach, Research Claims
Elena Sanz

Written and verified by the psychologist Elena Sanz.

Last update: 20 May, 2023

Although we separate them conceptually, in reality, our minds and bodies are connected. Therefore, our thoughts and moods affect our biology more than we might think. This is demonstrated by certain psychosomatic diseases and the well-known placebo effect. However, did you know that even your beliefs can fool your stomach? This is demonstrated by the experiment we’re going to discuss below.

As a matter of fact, this is a phenomenon that’s been verified in various contexts and experimental situations. It highlights a statement that might be difficult to believe. It’s the fact that you often don’t experience the consequences of what’s really happening, but of what you believe is happening. In many cases, this relationship is measurable through biological markers.

Woman thinking

How your beliefs can fool your stomach

As we mentioned above, the idea that beliefs influence biology isn’t new. Research regarding the placebo effect has shown that thinking that you’ve been given a remedy for discomfort can provide similar benefits to really being given one. On the other hand, its counterpart, the nocebo effect, demonstrates how an expectation of worsening or adverse effects leads you to experience them to a greater extent than if you hadn’t anticipated them.

This interconnection between mind and body has been investigated in the context of nutrition. It reveals how our expectations toward food can alter the way our bodies process it. One of the most interesting studies in this regard was published in the journal, Health Psychology. Researchers measured the behavior of ghrelin (a substance responsible for appetite) based on participants’ beliefs regarding the food they were ingesting.

The participants were divided into two groups. Both groups were offered a 380 kcal drink. However, some were told that they were going to consume a 620 kcal milkshake (the kind that we typically drink for fun and pleasure, despite knowing that it’s not recommended). The others were told that they would be drinking a healthy and nutritious shake of only 180 kcal (the kinds we tend to choose for health reasons, even though they’re not particularly appetizing).

The researchers measured participants’ ghrelin levels (a biological marker of hunger) three times:

  • Before starting the experiment.
  • During the anticipatory period. This was the moment at which the participants already knew what kind of shake they were going to drink. They were also shown a (misleading) printed image of the shake and a list of its components.
  • After consumption.

Amazing results

The results were surprising. In fact, they demonstrated that the behavior of ghrelin had changed based on what the participants thought they were consuming, rather than its actual nutritional value.

In the anticipatory period measurement, those who were waiting for the ‘indulgent’ shake experienced a moderate increase in ghrelin. This implied a physiological desire for the shake. On the other hand, those expecting the ‘sensible’ shake maintained normal levels of ghrelin.

After consuming the shake, ghrelin levels dropped dramatically in those who believed they’d consumed the high-calorie shake. However, in the other group, the levels remained the same. This suggested that the organism responds to expectations more than to reality. As such, our beliefs can fool our stomachs.

This process can have an effect on those individuals who seek to diet by consuming foods labeled as healthy, but which actually contain a high percentage of sugar and fat. Not only are they consuming unhealthy foods but, by considering them to be dietary, their ghrelin levels may not be adequately suppressed. Consequently, they don’t feel satiated.

Other studies

This isn’t the only time such findings have been observed. In fact, an experiment similar to the previous one was conducted with patients with type 2 diabetes. The participants all drank the same drink. However, they were induced (through misleading labels) to think that the drink they were consuming had either more or less sugar.

When measuring their blood glucose levels after ingestion, the researchers observed that the measurements varied based on what the individuals believed about their drinks and not on reality. This meant that those who thought they’d had a more sugary drink showed greater increases in glucose than the other group.

A similar effect was seen in a study designed to test beliefs about diet on weight loss. Participants were split into two groups. One group followed an isocaloric diet but was told they were on a calorie-deficient diet. The other group (the control group) was on a calorie-deficient regimen and was aware of this fact.

Both groups participated in the same exercise sessions for several weeks. The researchers discovered that the percentage of fat tissue, body mass, and BMI had decreased in the experimental group, but not in the control group.

man drinking

Your beliefs can fool your stomach, but not your thoughts

Many studies, including the above, draw attention to the important role of beliefs in food metabolism. Of course, this isn’t the only variable involved. Yet, psychological processes do appear to have a significant effect on physiological reactions.

That said, the previous findings shouldn’t make us fall prey to the kinds of magical or illusory thoughts that suggest we can control our physiology with our minds. Indeed, anticipating that a specific food is going to have a certain effect doesn’t necessarily mean that it will.

The responses of our bodies aren’t based on what we think in a specific way, but on what we believe with certainty. For example, people with diabetes know that sugar affects their glucose levels. This is the reality they experienced in the above-mentioned experiment.

In conclusion, the mind-body relationship needs to be studied in greater depth if we want to be able to use it to our advantage in terms of health care and well-being.

All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • 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.
  • Park, C., Pagnini, F., & Langer, E. (2020). Glucose metabolism responds to perceived sugar intake more than actual sugar intake. Scientific Reports10(1), 1-8.
  • Panayotov, V. S. (2019). Studying a possible placebo effect of an imaginary low-calorie diet. Frontiers in Psychiatry, 550.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.