The science behind the meat sweats

A  friend of mine asked that I write about an important medical condition that will likely afflict us all at one point in our lives (except perhaps vegetarians). A diagnosis involving discomfort, physiological distress, remorse, and possibly embarrassment. I am referring, of course, to the meat sweats.

Following a barbecue, particularly Korean or Argentinean in nature, or a rib-eating contest, one might find oneself feeling flushed, overcome by fatigue, and noticing a telltale dampness underneath the arms. As your body processes what it has just been forced to consume, you might begin to perspire profusely, purging liquid-protein through your pores.

While scientists posit that the meat sweats aren’t actually real, and indeed there are no academic papers dedicated to the topic, we carnivores know better.

There are a couple popular theories regarding the sweats, ranging from the high salt content in many cured meats – your body sweating more in an effort to expel the extra sodium – to the pure adrenaline experienced while eating another formerly living creature (apparently this is even greater if you hunt and kill the animal yourself).

Most likely though, the meat sweats are caused by the thermic effect of protein. While it may seem like every calorie you eat fixes itself permanently to your gut, the energy in food is conserved in several different ways. This includes fueling the process your body must go through to breakdown and digest what it is consuming. Remember the rumor that eating celery actually burns calories? This is purportedly because your body uses more energy to digest the fibrous vegetable than it contains (this is unfortunately not true, though you’re still unlikely to gain much weight on a diet of rabbit food).

As your body works to breakdown a meal, it begins to heat up, and just like any machine, the harder it works, the hotter it gets. Eating a lot of anything can cause this phenomenon, but a diet high in protein is particularly susceptible to turning you into a furnace. This is because protein has more than twice the thermic effect of fat or carbohydrates, with 15-35% of the energy consumed in a steak being required to digest it. This applies whether it’s chicken, hamburgers or tofu you’re chowing down on, though the soy sweats are a lesser-known phenomenon, probably because there aren’t many tofu-eating contests out there.

This thermic effect is one reason diets like Atkins and Paleo have taken off. However, before you dive face first into a plate of pulled pork, keep in mind that fat (the other main ingredient in bacon) has twice the energy density of protein at 9 calories per gram, but only burns off at a measly 5-10%.

So with barbecue season around the corner, try to control yourself and consume in moderation. But if this isn’t possible, prepare yourself a comfortable digestion spot on the couch, maybe with a towel underneath, and get ready to ride it out. At least you can be comforted that science is on your side.

Happy meating!

Exercise, endocannabinoids and natural highs

The benefits of exercise on the mind and the body are widely pronounced, with even moderate amounts decreasing the risk of heart disease, stroke, diabetes, dementia, depression, aggression, and Alzheimer’s, to name a few. Those of us who exercise regularly may also know first hand of the almost immediate mood-enhancing benefits of exercise, often touted as “runner’s high.” However, the exact mechanisms for this emotional boost are still unknown. Once believed to be the result of endorphins–natural opioid peptides released in the body that resemble synthetic opiates–that work as analgesics and create feelings of euphoria, this idea has recently come under scrutiny. The molecules creating these opioid peptides are too large to pass through the blood-brain barrier, meaning the endorphins released in the blood stream during exercise would be unable to make their way into the brain. However, a different endogenous drug system has begun to garner attention, and some researchers are now focusing on endocannabinoids, the organic derivative of cannabis, or marijuana, found in the body instead. Endocannabinoids are made up of lipids, or fat molecules, which are small enough to pass through the blood-brain barrier when released in the blood stream, and endocannabinoids have similar effects as opioids, reducing pain and anxiety and fostering feelings of well-being.

A number of studies published in recent years (and succinctly summarized here by the New York Times), have looked at the endocannabinoid system and exercise in mice and have found strong links between the two. Neuroscientists in Rome using single cell recordings in the striatum (the region touted as the pleasure center of the brain) discovered that both running and sucrose consumption increased the sensitivity of cannabinoid receptors in the striatum, indicating a greater activation of the pleasure system. This upregulation in cannabinoid transmission also helped to serve as a protective factor for the mice when stressors were introduced into the environment, providing neurological support for the claims that exercise can have strong emotional benefits, preventing stress, anxiety, and depression.

Another study investigating the pleasurable effects of running researched mice specifically bred without cannabinoid receptors in the brain. Researchers in France discovered that mice deficient in cannabinoid receptors ran 30-40% less over the course of a week than normal mice. Taken with the other mood-enhancing benefits of running, this further suggests that endocannabinoids are involved in the pleasure derived from exercise.

A seemingly paradoxical alternative effect of endocannabinoids is their role in eating, as well as exercise. Endocannabinoids are responsible for some of the pleasure derived from food, and in addition to the analgesic and anxiolytic effects, medicinal marijuana is also used to stimulate patients’ appetite, which can be affected by terminal illnesses or treatment. Recently, a team of scientists at the University of California, Irvine discovered that endocannabinoids not only provoke hunger and provide pleasure when we eat, but they also increase desire and urges for fatty foods in particular. In a study published this month in PNAS, researchers fed rats a sham liquid diet high in fat content (sham diets work by draining the contents of the stomach before the meal is digested, meaning that the taste and act of consumption are registered, but not the nutritional value or satiety signals that result from eating a meal). The diet high in fat, but not ones of primarily sugar or protein, selectively increased levels of endocannabinoids in the intestines. However, when the vagus nerve (responsible for taste) was cut, this increase of endocannabinoids in the stomach did not occur. This suggests that it is the taste sensation of the fat and communication from the brain to the GI tract that elicits this release. This elevation of endocannabinoids also affected metabolic processes in the stomach, creating a feedback loop where signals were sent back to the brain, creating a greater demand for more high fat foods. Conversely, when endocannabinoid antagonists (drugs that decrease the amount of endocannabinoids in the body) were given to the rats, they selectively consumed less high-fat solution but did not alter intake of their normal food chow. This study provides strong evidence for the fat-specific effect endocannabinoids have on appetite and craving, potentially creating a perpetuating cycle of demand and consumption of high-fat foods.

The paradoxical effects of endocannabinoids on the brain suggest that they have much to do with pleasure, and while they may encourage a binge on potato chips, at least they will also help you enjoy burning them off afterwards.