Cutting calories isn't just good for your waistline — it might also give you a health boost. Research has shown dialing back your calorie intake can help lower heart disease risk, improve insulin sensitivity in people with diabetes and bolster cognitive function.
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One (fairly simple) way to restrict calories is via intermittent fasting (IF). And there's a potential bonus to this approach: It just might make you happier, too.
Following an intermittent fasting diet and taking a probiotic supplement improved people's mental health, according to November 2020 research in Nutrients. Disclaimer: The study was quite small and, unfortunately, those who only did intermittent fasting (no probiotic) didn't reap the same mental health benefits.
If you recall, intermittent fasting is time-restricted eating, and there are a few different ways to execute it. You can fast on alternate days, for example, or follow a 5:2 eating pattern where you eat normally five days a week and eat very few calories two days a week. You could also eat during a four- to eight-hour window and fast anywhere from 16 to 20 hours a day.
The Connection Between Intermittent Fasting and Mood
Other research has found that restricting your calories alone may have mental health benefits. Indeed, a growing number of experimental studies are leading experts to think that intermittent fasting could have an antidepressant effect, according to a July 2015 review in Current Neuropharmacology.
Although much of the research seems to have been done in animal models, there are a handful of human studies that show promise. For instance, in a very small study of older men, those who followed a calorie-restricted diet via intermittent fasting for three months lowered their anger, tension and total mood disturbance — compared to the same-aged men who made no diet changes. The intermittent-fasting men's depression scores, however, weren't significantly changed, per a May 2013 study in The Journal of Nutrition, Health, & Aging.
Another study — this one looked at calorie restriction, not specifically intermittent fasting — found that adults who cut their calories by 25 percent for six months improved their mood and their depression score at the halfway mark (three months in) and at the end of the study, according to Physiology and Behavior research from April 2008.
Why Intermittent Fasting May Boost Your Mood
One theory is that calorie restriction increases the availability of neurotransmitters, such a serotonin and tryptophan, per the 2015 study in Current Neuropharmacology.
Another thought (from the same study) is that calorie restriction raises levels of the hunger hormone ghrelin, and ghrelin triggers a chain of reactions that have an anti-depressant effect.
And yet another plausible explanation is that intermittent fasting increases compounds that play a role in cellular cleansing (also called autophagy) and neurogenesis, according to a May 2018 Journal of Cellular and Molecular Medicine study.
Despite the potential mood-boosting benefits of intermittent fasting and calorie restriction, there's other research that suggests long-term calorie restriction could dampen mood and fuel depression.
Intermittent fasting is not a single solution for combatting depression. Your first line of defense for anything mental health-related should be a health professional's recommendation, such as medication and/or therapy. Because although the science appears to be promising, more research is still needed on the topic of fasting and mood — particularly among those with depressive symptoms.
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- J Nutr Healthy Aging: "Efficacy of fasting and calorie restriction (FCR) on mood and depression among ageing men"
- Nutrients: "PROFAST: A Randomized Trial Assessing the Effects of Intermittent Fasting and Lacticaseibacillus rhamnosus Probiotic among People with Prediabetes"
- Physiology & Behavior: "Effect of Caloric Restriction in Non-Obese Humans on Physiological, Psychological and Behavioral Outcomes"
- J Cell Mol Med: "Effect of caloric restriction on depression"
- Curr Neuropharmacol: "The Effects of Calorie Restriction in Depression and Potential Mechanisms"