If you have already forgotten to grab a granola bar for the day or maybe even (yes) on an empty stomach, you might recognize a strange feeling that comes over you after going without a snack longer than usual.
Is it vertigo? Joy? A little clarity? Well, it might be in your head. But there is also some scientific data, albeit preliminary, that suggests you wouldn’t imagine it – your fast can alter your mood.
Some forms of fasting – essentially abstaining from food intentionally – appear to have an effect on mood and have even been suggested as a treatment for conditions that can cause depressive symptoms and bad mood.
More than ever, lifestyle enthusiasts are dabbling in intermittent fasting everywhere. This is the practice of limiting eating over time, perhaps limiting eating to a certain time of day or eating every other day. Some proponents of the diet claim that it has a significant influence on their mood, which begs the question: do they really experience a change in mood as a result of the fast, or are they riding on a placebo effect?
It is safe to say that the science of the effects of fasting on mental health is in its infancy. But the research so far contains tantalizing clues about the influence of fasting on mood and mental health.
The science of fasting and mood
Studies of fasting – including intermittent fasting – and mood or mental health in humans tend to be hampered by several important factors, including small samples, unrepresentative participant populations, and poor design. mediocre study. But with these limitations in mind, scientists can use these preliminary results to open the door to new, more rigorous research.
These three studies are an example.
For example, in a 2018 study that looked only at people with multiple sclerosis, researchers created a diet in which some participants ate 22% fewer calories than usual each day of the week, while others practiced the 5: 2 diet. This is a kind of intermittent fasting in which people limit their calorie intake to 75% of baseline two days a week and eat whatever they want the other five days. The two groups were then compared to a control group, which made no change in their diet.
None of the MS symptoms of the participants considered in the study seemed to improve significantly, but the participants who dieted saw other benefits.
On the measure of MS symptoms used in this study, the emotional well-being of diet participants increased. Compared with those who did not change their diet, those who limited their calorie intake saw what the authors called a “clinically significant” improvement. Most importantly, there was no clear difference between dieting on an empty stomach or following a traditional calorie restriction diet every day.
In a different study from 2006, people with chronic pain who tried an 8-day prolonged fast also saw improvement in their mood compared to those in a control group who followed a low-calorie diet. Oddly enough, the mood benefits did not appear until the second half of the fasting period.
More recently, a June 2021 study of 22 adult women in Spain found that they reported improvement in symptoms of depression following a time-limited food intervention when they ate early in the day. But there was no control group for this study, so it’s hard to take the results at face value.
What to do with mixed results
As with a lot of things related to fasting and health, there is some evidence that blurs the lines when it comes to how it affects mood – or not. For example, a study of about 30 men in 2013 found that a combination of fasting and calorie restriction decreased their feelings of tension, anger, confusion and mood disturbances compared to the control group, which did not ‘made no change, but their depression scores did not improve.
And in fact, some evidence suggests the opposite is true: Fasting can have a negative influence on the mood of some people. A 2002 study describes how people with fatigue and pain went on a seven-day “fast” in which they ate 250 calories a day, and found it made no difference in their mood. On the contrary, the mood of some participants deteriorated.
And in another 2016 study, weightlifters who fasted for 48 hours didn’t seem to experience any difference in mood, except for anger levels, which worsened slightly.
It can also matter when you eat. A 2015 article describes how women who ate breakfast before exercise in the morning seemed to have a better mood at the end of the day than women who ate breakfast after exercise in the morning. This suggests that early morning fasting as part of a time-limited diet may not be good for mood.
The biology of fasting and mood
Only a handful of researchers have reviewed the scientific literature on fasting and mood or emotional well-being. A 2013 review attempts to analyze the biology that may be at play when it comes to mood swings and fasting. In this review, researchers refer to studies involving therapeutic fasting, which primarily involve people with certain health conditions who refrain from eating for more than a day or two.
One theory of how fasting influences mood is that during a fast, the levels of certain hormones can rise or fall when a person stops eating for an extended period of time. This, in turn, could trigger some sort of defense system in the brain.
In the body’s attempt to protect itself from the negative effects of higher than normal hormone levels, what the authors call “cellular stress resistance mechanisms” may come into play.
They identify a number of chemical changes found in the brain during fasting:
- The levels of the neurotransmitters (mainly chemical messengers) norepinephrine, epinephrine, dopamine, and cortisol may increase.
- Tryptophan and serotonin can increase.
- There is an increase in brain-derived neurotrophic factor, which is a protein linked to nerve growth.
- Leptin and insulin levels may decrease.
- There may be a decrease in the levels of thyroid hormones T3 and T4.
- Brain glucose – the sugar in your brain that it uses for energy – goes down.
- Endogenous endorphins can be released after prolonged fasting (5-10 days).
- Production of ketone bodies, which may be involved in “improving mood, decreasing pain sensation and promoting neuro-neuronal protection” in some cases.
And after – Human research may be thin, but there is more scientific evidence from animal studies and intermittent fasting. From this research, scientists gleaned evidence of fasting as a way to extend life and even prevent diabetes, cancer, and cardiovascular disease. But studying mood disorders or emotional well-being in mice in the lab presents obvious challenges. By trying to translate such science to humans, this effect could be magnified.
The human studies that do exist are a good start, but they are relatively small, short-term, and inconsistent.
But because mood disorders and depression are so difficult to treat, more high-quality research in humans is badly needed. Psychiatric drugs may not work in some cases, or may be unaffordable.
If there was some kind of fasting that could improve mood or relieve symptoms of depression, it could be an inexpensive way to lead a happier life.