We Crave Interacting With People the Same Way We Crave Food
A recent study reveals a link between fasting and social isolation.
Posted March 4, 2021
So much of our biology services being social. We are social beings. Unfortunately, things can happen and challenge this biology. The COVID19 pandemic flourished in 2020. As a result, lockdowns were mandated at different times across the world. Top recommendations include social distancing and wearing face masks. This gave birth to another pandemic that is still unfolding at an alarming rate, namely the mental health penalties of social isolation. Deficits in social needs have been studied in many organisms including ants, mice, monkeys and human beings. Recently, a study revealed an important link between food deprivation and social isolation.
What do food cravings have in common with loneliness? One MIT study showed that they have a lot in common. The MIT research team collected data back in 2018 and 2019 before the Coronavirus pandemic-related lock-downs were implemented. However, the results explain what COVID-related social isolation might be doing to the brain. They recruited 40 healthy participants and confined them to a windowless room on MIT’s campus for 10 hours. The participants were not allowed to use their phones. The researchers went out of their way to make sure that the volunteers were socially isolated. For example, if a participant had to go to the bathroom, researchers made sure that the bathrooms were empty. They were not allowed to see people. After the 10-hour isolation, the participants were scanned in an MRI machine. To make sure that they do not have any social conversations even with LAB assistants, researchers trained participants in how to get into the MRI machine on their own! The same people underwent 10 hours of fasting from food on a different day. Similarly, after the 10-hour fast, the participants were scanned. In both conditions participants were looking at food, people interacting, and neutral images while being scanned in the MRI. It has been shown in previous studies that looking at food after fasting activate the ‘craving circuit’ in the brain. The researchers in this study focused on midbrain regions of the craving circuit (also involved in reward). Indeed, midbrain exhibited selective responses to food images after fasting from food for 10 hours.
But how about ‘fasting’ from social interactions? The researchers conducted a multivariate pattern analysis of midbrain regions to find out if social fasting and food fasting exhibit the same pattern of brain activation when looking at relevant cues, people or food, respectively. The study showed that the midbrain regions of participants who were socially isolated for 10 hours responded to images of people in similar ways to hungry participants looking at food. The more participants self-reported that they wanted food (after fasting) or social interaction (after isolation), the higher the midbrain activity. These findings strongly suggest that people who are forced to be socially isolated crave interactions in the same way a hungry person craves food!
Deprivation of a specific need may serve to narrow the focus of our motivation system. In other words, the motivation system becomes dedicated to attaining the deprived need and simultaneously reduce resources available to get other satiated needs. So, when a person is hungry, ‘getting food’ will monopolize the motivational system and thus less motivation for other needs such as social connection will be available. That is what the findings of one study suggested; hungry people tend to be less prosocial (2). The reciprocal does not seem to be supported. When animal models are socially deprived, they actually increase (not decrease) food consumption and substance addiction (3). Such findings suggest that deprivation of a specific need such as social connection broadens (not narrows) our motivational range for needs. Tomova and colleagues integrate these seemingly opposite findings (1). The key to solving this puzzle is ‘time’. Short-term social deprivation may lead to temporary narrowing, whereas long-term social deprivation may lead to compensations by being more responsive to nonsocial needs (broadening motivational range). Thus, social isolation leads to changes in behaviors, specifically behaviors pertaining to reward-seeking and motivation. Keep in mind that social isolation was temporary and limited to 10 hours, participants knew exactly when the isolation would end, and they can quit if they want to.
How about involuntary chronic social isolation? A study published in the Annals of The New York Academy of Sciences proposed that we have a social 'homeostat' (like a thermostat) (4). Our bodies have a somewhat pre-set level (homeostasis) for many things such as temperature, salt, and energy. When levels deviate in either direction from homeostasis, our brain initiates many responses to bring us back to homeostasis though compensatory mechanisms. Researchers Matthews and Tye assert that social isolation expressed as feelings of loneliness disrupts a pre-set homeostatic socialization system (4). As a result, behavioral and neural adaptations are generated to deal with this deviation from homeostasis. With chronic social isolation, these failed rescue attempts result in increased risk for diseases and mortality. Indeed, there is plenty of evidence for the effects of prolonged loneliness on health and mortality (5).
Loneliness is not synonymous with social isolation. It is a perception! A person can feel lonely in a room full of people. Social distancing should be highly encouraged during the pandemic and replaced with physical distancing. Some ways to connect deeply with others is to bond over shared values, interests, and meaningful discussions. Concrete examples include joining a book club, FaceTiming loved ones and virtually discussing interesting talks.
(1) Tomova, L, Wang, K.L., Thompson, T….Saxe, R. (2020). Acute social isolation evokes midbrain craving responses similar to hunger. Nature Neuroscience, 23, 1597-1605.
(2) Fraser, S. & Nettle, D. Hunger affects social decisions in a multi-round Public Goods Game but not a single-shot Ultimatum Game. (2020). Adapt. Human Behav. Physiol. 6, 334–355.
(3) Schipper, L., Harvey, L., van der Beek, E. M. & van Dijk, G. Home alone:
a systematic review and meta-analysis on the effects of individual housing on body weight, food intake and visceral fat mass in rodents. (2018). Obes. Rev. 19, 614–637.
(4) Matthews, G. A. & Tye, K. M. Neural mechanisms of social homeostasis. (2019). Ann. N.Y. Acad. Sci. https://doi.org/10.1111/nyas.14016.
(5) Holt-Lunstad, J., Smith, T.B. & Layton, J.B. (2010). Social relationships and mortality risk: a meta-analytic review.