Caloric restriction can boost levels of brain-derived neurotrophic factor (BDNF), which is considered to play a critical role in mood disorders.For more than a century, fasting has been espoused as a treatment of supposed “great utility in the preservation of health,” especially rejuvenating the body and, above all, the mind. When people fast for even 18 hours, though, they may get hungry and irritable. After one or two days, positive mood goes down and negative mood goes up, and after three days, fasters can increasingly feel sad, self-blame, and suffer a loss of libido. Then, something strange starts to happen: People experience a “fasting-induced mood enhancement…reflected by decreased anxiety, depression, fatigue, and improved vigor.” Studies tend to show this across the board. Once you get over the hump, fasters frequently experience “an increased level of vigilance and a mood improvement, a subjective feeling of well-being, and sometimes of euphoria.” And, no wonder, as, by then, endorphin levels may rise by nearly 50 percent, as seen here and at 1:06 in my video Friday Favorites: Fasting to Treat Depression. This enhancement of mood, alertness, and calm makes a certain amount of evolutionary sense. Our body wants us to feel poorly initially so we continue to eat, day to day, when food is available, but if we go a couple of days without food, our body realizes we can’t just mope in our cave; we need to get motivated to go out and find some calories.So, can fasting be used for mood disorders, like depression? It’s great that people can feel better after a few days of fasting, but the critical question revolves around the “persistence of mood improvement over time” once fasting ends and eating resumes. The little published evidence we have comes out of Japan and the former Soviet Union, and some of it is just ridiculous, like this study that included women with a variety of symptoms, which the researchers blame mostly on marital conflict, as you can see below and at 2:08 in my video. Husband not treating you right? How about some “electroshock therapy”? That didn’t seem to help much, so what about “hunger therapy”? Of course, starving the women made them hungry, but that’s what Thorazine is for. If they keep getting injected with an antipsychotic to calm them down, they can sail right through. So, what happened in the study? What would we even do with those results? Another study, however, skipped the Thorazine. The participants fasted for ten days, but they were also kept in bed all day on “absolute bed rest,” completely isolated and “prohibited from seeing other people except the attending doctor and nurse…also denied access to television, radio, newspapers or any other forms of information.” So, if people got better or worse, it would be impossible to tease out the effects of the fasting component on its own. But researchers found that they apparently did get better, with efficacy reportedly demonstrated in 31 out of 36 patients suffering from depression, as seen here and at 2:56 in my video.The researchers concluded that fasting therapy may provide an alternative to the use of antidepressant drugs, “thinking the fasting therapy may be a kind of shock therapy.” People are so relieved to be eating again, to get out of solitary confinement, and to even just get out of bed that they report feeling better. That was at the time of discharge, though. How did they feel the next day, the next week, the next month? Fasting is, by definition, unsustainable, so what we want to ideally see are some kind of longer-lasting effects.Researchers did a follow-up with a few hundred patients, not just a few months later, but after a few years. Of the 69 who were evidently suffering from depression, 90 percent reported feeling good or excellent results at the end of the ten-day fast, and, remarkably, years later, 87 percent of the 62 individuals who replied claimed that they were still doing well. Now, there was no control group, so we don’t know if they would have done just as well or even better without the fast, and it was all self-reporting, so there may have been a response bias where participants tried to please the researchers. Who knows? Maybe they were afraid they’d get sent back to solitary if they didn’t respond affirmatively. We have no idea, but we do have good evidence for the short-term mood benefits.Why would fasting improve feelings of depression? In addition to the endorphins and the surge in serotonin, the so-called happiness hormone, when we fast, there is a bump in brain-derived neurotrophic factor (BDNF), which is considered to play a crucial role in mood disorders. Researchers have perked up rodents with it, but we aren’t rats or mice. What about us? Humans with major depression have lower levels of BDNF circulating in their bloodstream. Autopsy studies of suicide victims show only about half the BDNF in certain key brain regions, compared to controls, suggesting it may play an important role in suicidal behavior, as seen here and at 4:38 in my video. We can boost BDNF with antidepressant drugs and electroshock; we can also boost it with caloric restriction. We can get a 70 percent boost in levels after three months of cutting 25 percent of calories out of our daily diet, as shown below and at 4:51.Is there anything we can add to our diets to boost BNDF levels so we can get the benefits without the hunger? We’ll find out next.