The average waistline of people in the developed world has increased
dramatically in just the last 25 years, with three-quarters of adults now overweight or obese. For the first time in history, there are literally more people overweight than there are starving.

One part of the problem is the food distribution system. In the absence of any real oversight, the industrial food system has evolved to give people exactly what they want, and exactly what they don't need - the immediate gratification of high-calorific food. The muffin I was served for breakfast on a recent flight across the US was so insanely sugar-rich, a few crumbs of it would sweeten your coffee.

The other part of the problem is that our brains have terribly weak circuitry for inhibiting impulses, especially impulses that look delicious. The brain network involved in impulse control sits inside the smallest, most easily overwhelmed region of the brain, the prefrontal cortex. Like our limited ability to do complex calculations in our heads, impulse control is a limited resource that tires with each use.

Put these two issues together - cheap resources available everywhere and poor self-control - and you get a weight problem literally of epidemic proportions. The trouble is, this same phenomenon may be happening with our minds. If current trend continues, we could see millions of people's minds becoming as unhealthy and dysfunctional as their stomachs. The reason? Social media.

Social Issues Are Primary
My ultra-sugared breakfast muffin contained what are sometimes called 'empty calories'. Empty calories make you feel better in the short term, but your brain then craves more when you crash from the sudden sugar high. Plus there's no nutritional goodness like this is in more complex foods. I have sense that we are rapidly moving toward giving people 24/7, easy access to 'empty neural calories'. These calories, in the form of perceived social connectivity, increase the overall stimulation of the brain, but may not do much to make our brain more integrated, adaptive or functional. In fact, just like sugar, some types of neural stimulation have you wanting more and more, without ever feeling satisfied. The result can be a reduction in healthy neural functioning, in the form of a reduced ability to focus.

The reason that some online social interactions may over-stimulate the brain is that social connections, (which means simply being in a social exchange with another person) are classed as primary rewards by the brain. Social connections are tagged as something deeply useful to survival. Your brain likes to feel it has the resources of people around you. As a result, your brain craves social connections using similar circuitry to how it craves sugary food. Both sugary foods and positive social connections activate the reward circuits in the ventral striatum, releasing dopamine into the prefrontal cortex.

One way to understand this is to explore what happens in the absence of social connections. University of Chicago social neuroscientist John Cacioppo led a study of 229 people between 50 and 68 years old, finding a 30-point difference in blood pressure between those who experienced loneliness and those with healthy social connections. Loneliness, the study showed, could significantly increase the risk of death from stroke and heart disease.

As Cacioppo tried to understand the data, he realized that loneliness might be more important than society generally realizes. "Loneliness generates a threat response," Cacioppo explains, "the same as pain, thirst, hunger, or fear." Being connected to others in a positive way, feeling a sense of relatedness, is a basic need for human beings. An absence of glucose in the blood occurs as hunger, which makes you feel anxious until resolved with a good feed. The absence of social connections also generates a type of hunger. This is a hunger otherwise known as 'loneliness' that also makes you feel anxious until it's resolved.

It is this hunger that starts to explain the incredible success of organizations like Facebook and Twitter. When you connect with people online, you're getting a little zing in your reward center, which makes you want to stay there and keep zinging.  Don't blame Facebook - like the food distribution system, they have just worked out what people most want, and are giving it to them as richly and intensely as possible. Social media sites are like an online candy store for your social brain.

'Empty Neural Calories'
So far, so good. The trouble is, like a syrupy muffin, connecting socially online may be like eating empty calories.  The circuitry activated when you connect online is the 'seeking' circuitry of dopamine. Yet when we connect with people online, we don't tend to get the calming effect of oxytocin or seratonin that happens when we bond with someone in real time, when our circuits resonate with real-time shared emotions and experiences. As a result, you want more and more social connections. On Twitter, you rarely get to feel satisfied and 'full' the way you might if you chatted in person with 50 people at a conference (after which you'd want nothing more to do with people for a while as your circuits recovered.)

This problem was laid out well in a piece in Slate magazine. In summary, there's a circuitry for 'seeking' and a circuitry for 'liking'. The 'liking' response settles down the excitement of the 'seeking' circuitry. Without the 'liking' response, we act like that rat that keeps pressing a level over and over to get a little dopamine hit directly into the brain, forgetting all about food and rest.

To the brain, simply receiving new information activates the reward circuitry: information itself can be rewarding, which prompted neuroscientist Jonah Lehrer to coin the term 'information craving.' Thus people can easily become addicted to getting information quickly and often. The social circuitry does the same thing, only sometimes more intensely. One new study, (still under review) showed that a computer saying 'good job' in an experiment activated people's reward circuitry as intensely as financial rewards.

Too much social seeking isn't good for you
The trouble with such ready access to empty social rewards is that we just keep wanting more. As this reward-seeking circuit fires up, our ability to hold more subtle ideas in mind diminishes proportionally to the increased activation of the limbic system, which becomes aroused up with strong rewards or threats. An aroused limbic system results in the de-activation of prefrontal regions needed for executive control. An over-abundance of dopamine, while it feels good on one level, just as a sugary muffin does, creates a mental hyperactivity that reduces your capacity for deeper focus. It is also likely to reduce one's ability to have more subtle insights, the kind required to solve complex problems. The ability to have insights is linked to one's capacity to notice 'weak activations' which can be easily overwhelmed by the intense neural activity of a dopamine rush.