You’re eating healthy, working out regularly, and you’re in a good relationship. Life is good. This means you should never feel stress again, right? Ha! If only. Unfortunately, living stress-free isn’t something most of us will experience. It’s a part of life. But the key is to manage our stress well and try not to bring more upon ourselves than life is already planning to send our way. However, many people add extra stress to their life by following rigid weight loss protocols that lead to intense concerns of “am I doing it exactly right?” One protocol that’s gained immense popularity in recent years is intermittent fasting (IF). But if you already have enough stress on your plate, or even if you’re feeling groovy, IF may not be something you want to take on. Let’s talk about why not. Fasting in itself is by no means a new practice. It is featured in all the major religions of the world, typically used as a means to increase self-control and to draw closer to the divine. Though as Marc David stated, “There are no historical references to fasting so as to look better in a bikini.”1 Other posts on this site detail what IF is or how it’s done, and talk about the benefits of IF. This article is about the other side of the coin. How IF can be stressful on the body, where it can lead to dangerous situations, and why you may want to consider avoiding it.

Intermittent Fasting and the Central Nervous System

Fasting, ideally, happens every night while we sleep. This allows the body a period of time to focus on detoxifying and rebuilding rather than digesting food. Your parasympathetic nervous system (the “rest and digest” branch) is at work during the night while you’re in an anabolic (“building up”) state. It is suggested by many IF advocates that continuing the fast during waking hours may allow those benefits to continue and be a positive experience for many people. Where trouble can occur is that during those conscious hours you become keenly aware of how hungry you are, perhaps fixating on your stomach, the clock, and when you’re next meal will come. You’re sympathetic nervous system (the “fight or flight” branch) is fired up, feeling the stress, and is ready to help you flee you to safety. The sympathetic nervous system is literally something our species wouldn’t exist without. It works to provide energy in short bursts as part of our innate escape from danger response. But it’s not supposed to be steering the car all the time. The problem is, even though we’re not running from tigers any more, many people are constantly dealing with stressors that over stimulate the sympathetic nervous system. When fasting becomes a cause of stress, your cortisol levels shoot through the roof, adrenal glands become fatigued, next thing you know you’re tired, sluggish, cranky, gaining weight, and a danger to fellow drivers when you get behind the wheel! (No joke. Each year during Ramadan, the annual Muslim practice of fasting from sunrise to sunset for an entire month, reports show decreases in daytime alertness, mood, wakefulness, competitive athletic performance, and increases the incidence of traffic accidents, not surprisingly, between 8am and 2pm.2,3)

Intermittent Fasting Can Affect Men and Women Differently

The issue of elevated stress during fasting is particularly concerning for women. Low calories naturally lead to lower energy, induce stress and affect hormones in both men and women, but it happens faster in women. Many women find that with intermittent fasting comes sleeplessness, anxiety, and irregular periods, among a myriad of other symptoms of hormone irregularities. Fasting sends a message of, “No food! Be careful! By no means reproduce!” For men, reproducing during famine would be a slight inconvenience. One more mouth to feed being the penalty for a night of fun (probably not his best performance though :). For women, the risks of reproducing during famine are much more severe. It increases the likelihood of dying during childbirth or nursing, as well as elevates the risk of birth defects. Restricting calories signals famine to a woman’s body and decreases fertility (alters hormones) until food supplies return to levels that can support reproduction. Or, in the opposite direction, it signals, “Be fertile quickly (early puberty), reproduce quickly, and get out of the way (die)”. Some women counter this argument stating that they actually feel more energy during fasting phases. There’s an evolutionary explanation for this also. One of the effects of fasting is the stimulation of hypocretin neurons, small particles in the brain that prevent the body from falling asleep. Why would your body turn these on? If you’re hungry, well then damn it! You better get out of bed and go find some food! We need to make a careful distinction between feeling a burst of energy and true well-being.

Fasting = Stress

Bottom line, fasting is a stressor. Period. It just is. Even the avid proponents of intermittent fasting agree. But what they do is barely stick a little asterisk at the end of their blog posts saying: *people who are stressed should probably not fast. Probably is right. And here’s a major consideration for both women and men. Commonly cited benefits to fasting are improved insulin sensitivity, bodyweight and body fat, blood pressure, blood lipids (for men only4), heart rate, and glucose tolerance (again, for men only4). All of these benefits can be achieved by exercising, with none of the stressors of fasting.5,6 And while research on animals regarding fasting have consistently found these benefits to be true, human research is much more scarce and inconsistent, showing both benefits and risks. Furthermore, the effects of skipping breakfast in particular have been extensively studied. Overall, the evidence points to regular breakfast consumption improving cognitive function, memory, and nutrient status. Skipping breakfast has been shown to decrease post-meal insulin sensitivity and increase LDL-cholesterol7. This data points to the possibility that the body is "metabolically primed" to eat a meal soon after an overnight fast. Also, working out while fasting, an approach commonly encouraged by IF proponents, has been shown to increase muscle damage.8 In another study conducted on exercising during fasting, cortisol levels rose by 105% by the end of the training routine, where the control group who had consumed a healthy combination of protein and carbohydrates within four hours prior to the workout saw no increase in cortisol levels. 9 Back to evolution, when you work out hungry, your body’s doing it’s job by firing up the sympathetic nervous system and helping you flee the chasing tiger.

Intermittent Fasting, the Bottom Line

To be clear, the message isn’t that fasting of itself is bad and that no one should ever do it. Fasting can be a beautiful thing that can lead to intense spiritual experiences as well as physical highs. If you feel good doing it, feel good about yourself, or find it as a way to draw closer to the divine or gain insight to your own life, by all means pursue it. But there are risks to consider. Look at the options, be honest about your priorities, and listen to your body with love and kindness. Is fasting worth trying if one is overweight and wants to improve her metabolic markers, and has been frustrated with results so far? Maybe. What if you’re of normal weight, or a light sleeper? Or if periods become irregular, acne appears, or the appetite becomes intense or disappears altogether? There are certainly alternatives to keep in mind. All of us, men and women, need to make conscious, intent decisions with our mental, physical, and emotional health at the forefront of our minds. We’re all different. Just because IF is popular and works for some people doesn’t mean it’s the right thing for you. If you’ve already got enough on your plate, even if life is good but especially if you’re already stressed, remember that the biggest benefit you can get from what you eat comes from how you think about what you eat. Bottom line: Relax, exercise doing activities you enjoy, have a bite of dessert, and send a clear signal to your brain and body that life is good. You’re happy. There is plenty of good healthy food around. There are no tigers chasing you. Smile. Have you tried intermittent fasting? What has been your experience? I'd love to hear from you in the comment section below.

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Sources 1. Marc David, founder of the Institute for the Psychology of Eating 2. Roki R, et al. Physiological and chronobiological changes during Ramadan intermittent fasting. Ann Nutr Metab. 2004;48(4):296-303. Epub 2004 Sep 24. 3. Bener A, et al. Road traffic injuries in Al-Ain City, United Arab Emirates. J R Soc Health. 1992 Dec;112(6):273-6. 4. http://www.ncbi.nlm.nih.gov/pubmed/15833943?dopt=Abstract 5. Lakka TA, Laaksonen DE. Physical activity in prevention and treatment of the metabolic syndrome. Appl Physiol Nutr Metab. 2007 Feb;32(1):76-88. 6. Carrol S, Dudfeld M. What is the relationship between exercise and metabolic abnormalities? A review of the metabolic syndrome. Sports Med. 2004;34(6):371-418. 7. Farshchi HR, et al. Deleterious effects of omitting breakfast on insulin sensitivity and fasting lipid profiles in healthy lean women. Am J Clin Nutr. 2005 Feb;81(2):388-96. 8. Baty JJ, et al. The effect of a carbohydrate and protein supplement on resistance exercise performance, hormonal response, and muscle damage. J Strength Cond Res. 2007 May;21(2):321-9. 9. Bird SP, et al. Liquid carbohydrate/essential amino acid ingestion during a short-term bout of resistance exercise suppresses myofibrillar protein degradation. Metabolism. 2006 May;55(5):570-7.