 For over a century, fasting has been espoused as a treatment of supposed great utility in the preservation of health, especially rejuvenating the body, but above all, the mind. But fast people, even just 18 hours, and they get all hungry and irritable. After one or two days, positive mood goes down, negative mood goes up, and by 72 hours people can feel sad, self-blaming, and suffer a loss of libido. But then something strange starts to happen. After a few days, people experience a fasting-induced mood enhancement, decreased anxiety, depression, fatigue, and improved vigor. And that's what studies tend to show across the board. Once you get over the hump, fasters frequently experience an increased level of vigilance and mood improvement, a subjective feeling of well-being, and sometimes even euphoria. And no wonder, as by then your endorphin levels may shoot up nearly 50%. This enhancement of mood, alertness, and calm makes a certain amount of evolutionary sense, yet your body wants you to feel crappy initially so you continue eating day-to-day when food is available. But if you go a couple of days without food, your body realizes it can't have you moping back in the cave. You've got to get motivated to get out there and find some calories. So can fasting be used for mood disorders like depression? Yeah, it's great that you can get people to feel better after a few days of fasting, but the critical question revolves around the persistence of mood improvement over time once you start eating again. You don't know until you put it to the test. Interestingly, 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, which included women with a variety of symptoms, which the researchers blame mostly on marital conflict. Oh, husband not treating you right? How about a little electroshock therapy? That didn't seem to help much, though, so what about hunger therapy? Of course, starving those women made them hungry, but that's what Thorazine is for. If you keep injecting them with an antipsychotic to calm them down, they can sail right through. So what happened? Who cares what happened? We even do with those results, right? But this other study skipped the Thorazine. Ten days of fasting, but they also kept them in bed all day, completely isolated with no contact with the outside world. So yeah, if people got better or worse, it'd be impossible to tease out the effects of just the fasting component, but they did apparently get better. With efficacy supposedly demonstrated in 31 out of 36 patients suffering from depression. They conclude that fasting therapy may provide an alternative to the use of antidepressant drugs, considering it a kind of shock therapy. People are so relieved to just be eating again to get out of solitary confinement, to even just get out of bed, they report feeling better. Yeah, but that was at the time of discharge. How did they feel the next day, the next week, the next month? Fasting is by definition unsustainable, so ideally what we want to see is some kind of longer lasting effects. What the researchers did was follow up with a few hundred patients, not just a few months later, but a few years later. Of the 69 who were evidently suffering from depression, 90% reported feeling good or excellent results at the end of the 10-day fast. And remarkably, years later, 87% of the 62 that replied claimed that they were still doing good. Now, there was no control group, so we don't know if they would have done just as well or better without the fast. It was just self-report, so maybe there was response bias, where you try to please the researcher, or maybe they were afraid otherwise they'd get sent back to the hole, and we have no idea, but we do have good evidence for the short-term mood benefits. The question is why? In addition to the endorphins when you fast, the surgeon serotonin-circlet happiness hormone, there is a bump in BDNF, brain-derived neurotropic factor considered to play a crucial role in mood disorders, and it's not just because you perk up rodents with humans with major depression, have lower level circulating in their bloodstream, autopsy studies of suicide victims show only about half the BDNF in certain key brain regions compared to controls, suggesting they play an important role in suicidal behavior. You can boost BDNF with antidepressant drugs and electroshock, or with calorie restriction, a 70% boost in levels after three months cutting 25% of calories out of their daily diet. But is there anything we can add to our diets to boost BDNF levels so we can get the benefits without the hunger? We'll find out next.