The first rule of intermittent fasting is that it is not about skipping meals for no reason, just because the schedule won’t stretch any further or because we don’t have time or desire to cook. There is a time window to help and minimum intakes of essential nutrients that must be reached within that window.
That’s why it isn’t a good idea to fit fasting into moments of stress. What you perceive as a grand plan that saves you time at the table triggers alarms in your survival instinct.
A Very Bad Combination
A meta-analysis published in the scientific journal Stress shows that skipping meals suddenly activates our hypothalamic-pituitary-adrenal axis. In layman’s terms: if cortisol is sky-high due to your daily rhythm, depriving the body of energy will send a red alert signal to the brain. Something like ‘there is scarcity and we are in danger’. But are we really?
“It depends on the type of fasting, the duration, the timing, sleep, physical activity and the person’s health status. Fasting sends a metabolic signal of energy shortage, and cortisol participates precisely in mobilizing glucose and fats when the body needs fuel,” reveals María Riestra Fernández, specialist in the nutrition area of the Spanish Society of Endocrinology and Nutrition (SEEN).
Works in Calm Periods
In a calm person, well-rested and with a good relationship with food, a moderate fast can be tolerated well, assures the expert. However, in a phase of high stress, anxiety, poor sleep or a heavy workload, adding more hours without eating can be an extra demand. “There, the sensation of nervousness, irritability or fatigue” may increase.
If we look at recent studies, “the effects of intermittent fasting on cortisol and circadian rhythms vary according to the protocol. Prolonged fasts do tend to be associated with an increase in cortisol”. The conclusion is, above all, common sense: do not demonize intermittent fasting, “but don’t impose it during moments of elevated stress,” adds Dr. Riestra Fernández.
More Irritable and with Less Energy
You’ve probably heard that bad mood that comes on when we’re hungry. And there is a reason. “The brain needs a supply of energy. If we sleep poorly, we’re tense and, in addition, we delay the first meal a lot; the body may pull more alert hormones, like cortisol and adrenaline, to keep glucose available. That can make us operate in emergency mode.”
This makes us more irritable, reduces concentration, adds a feeling of weakness, headache, anxiety to eat at the end of the day or worse tolerance to exercise. It doesn’t happen to everyone, but it is common.
“Another consequence of pairing fasting and stress is arriving at the next meal with too much hunger. Then it’s easier to eat quickly, choose very caloric foods or lose the sense of control,” warns the SEEN expert. She also highlights people with a history of eating disorders, anxiety, pregnancy, diabetes treated with medications, or underweight: in these cases fasting should be avoided or done only under medical supervision.
A recent study published in Nutrients confirms that fasting works very differently depending on your psychological state. It yields very interesting results when we are calm, but if you already carry anxiety, fasting tends to manifest as unbridled irritability, fatigue and emotional fluctuations.
With Cortisol Sky-High, Better Not Eliminate the Meal
And how to know when to take a break from intermittent fasting when stress appears? Both the consulted expert and the studies speak of sustained stress. “There is no need to pause it automatically at any fleeting moment, but yes if it is intense, sustained or arrives accompanied by anxiety, insomnia, irritability or a drop in energy. Nutrition should help sustain health, not become another pressure,” she adds.
A reasonable and flexible strategy would be, instead of a strict 16:8, to switch to a gentle 12-hour nocturnal fast. “Have dinner at a reasonable hour and breakfast on waking or mid-morning. Another option is to maintain regular schedules, prioritizing protein, fiber and healthy fats to avoid spikes and sharp drops in hunger. In reality, the key is to observe signals: sleep, energy, mood, menstrual cycle, athletic performance and relationship with food. If everything worsens, it’s not the time to make changes,” she adds.
Anti-Stress Mediterranean Diet
Although there are no foods that magically eliminate anxiety, there are eating patterns that help stabilize energy and appetite. The foundation, once again, is the Mediterranean diet: vegetables, fruits, legumes, whole grains, olive oil, nuts, fish, eggs or fermented dairy. “This pattern is associated with better mental health and sleep outcomes, although it does not replace psychological treatment when needed,” highlights María Riestra Fernández.
The expert offers concrete ideas: for breakfast, it’s better to combine three elements: protein, fiber and healthy fat. “For example, natural yogurt or kefir with oats, fruit and nuts; whole-grain toast with egg and tomato; or fresh cheese with fruit and seeds. This usually satisfies more than a breakfast of coffee and pastries. For lunches and dinners, a simple plate: half a plate of vegetables, a quarter of protein (legume, fish, egg, chicken, tofu) and a quarter of quality carbohydrate (potato, brown rice, whole-grain bread, quinoa). If we have high stress, it’s not advisable to have a very small dinner: a light but complete dinner can better support rest than going to bed hungry,” she says.
Another thing that helps the body is predictability: relatively stable meal times, not arriving at meals ravenous, and avoiding relying on coffee in the morning to fuel a nocturnal binge.
Aerobic Exercise, Strength and Yoga
To mitigate the anxiety that the absence of food triggers in many people, experts suggest engaging in some form of physical activity, even yoga, Pilates, tai chi and outdoor exercise. “If stress is very high, it isn’t always advisable to add very intense workouts, especially while fasting and sleeping little. High-intensity exercise can be healthy, but it can also be a physiological load, and at those times a combination of brisk walking, moderate strength, mobility, yoga or outdoor activities tends to work better,” says the nutrition specialist.
In any case, “exercise should not be another stressor; it should be a channel of release and recovery,” she concludes.
