Large variations have been observed in individual responses to fasting, meal timing and frequency. This post from Breaking Muscle examines the long-standing beliefs about eating healthy.
When I started out in practice, around twenty years ago, a few things were tantamount to being sacred in nutrition. One was that you must eat breakfast, another was that you must eat at least five small meals per day. But nowadays, meal timing and frequency is certainly not as important as was once thought, and clinically, we observe large variations in individual responses to both meal timing and frequency. Whereas we have been told that we need to drip-feed nutrients into the system, we now know that more infrequent feedings are completely appropriate for many people.
The Physiology of Fasting
One of the things that changed my experience of meal frequency was fasting. Back in the early days of my practice in the late 1990s and early 2000s, I was working with Islamic clients. They wondered (as did I) about the effects of Ramadan fasting on health. I searched the available literature to see what effects fasting had on health and performance. I was surprised to find that what little evidence there was at the time suggested no negative effects on health, and this shook my ‘frequent eating’ dogma to its core.
Since then I have used fasting protocols for a variety of reasons (some mental, emotional, and spiritual). Fasting isn’t for everyone, and I wouldn’t say that it’s essential, but knowing that it exerts some benefits provides another reason not to be overly fastidious about having to eat “by-the-clock.”
There are now hundreds of papers on intermittent fasting. Reviews of these papers suggest that intermittent fasting results in weight-loss and improved cardiometabolic risk factors, including improved blood glucose profiles, insulin, cholesterol profiles, and inflammatory markers.1, 2Experience from Ramadan studies on athletes also suggests that physical fitness is not negatively affected, and athletes who maintain an appropriate calorie (fuel) intake, hydration and preserve sleep length, don’t suffer a reduction in performance doing this type of fast.3, 4
This makes complete sense if we think about the physiology of the human organism. We are extremely well adapted to go through periods of fasting and periods of feeding. When we are active during the day, we are sympathetic nervous system (SNS) dominant. This is our so-called ‘fight or flight’ response. In this state, we release higher levels of the stress hormones, especially epinephrine and norepinephrine. These allow greater cognition and alertness (unless of course you are overstimulated after drinking one too many espressos), and help the body to free up glucose for immediate use as fuel.
Stop Daily Grazing
The body also seeks to prioritize blood supply to working muscles, and reduces blood flow to the gastrointestinal tract, visceral organs, closes gastric sphincters (valves), and reduces motility (movement of food) through the bowel. These aspects of the stress-response reduce our ability to utilize food effectively during times of activity.
So, it doesn’t make a lot of sense to eat while extremely active, unless of course you are involved in long periods of exercise in which you need to fuel, if you are taking small amounts of macros to enhance protein synthesis, refuelling, or using post-exercise recovery. You certainly don’t need to be constantly grazing through your working day. In fact, I think that if you need to constantly fuel your body, you are most likely metabolically disordered.
Parasympathetic nervous system (PSNS) dominance, is known conversely as the ‘rest and digest’ system. In this state, we relax, gastric enzymes and hydrochloric acid are produced in greater amounts, and movement of food through the bowel is prioritized.
Eat When You’re Hungry
For the reasons outlined above, when people ask what they should eat when ‘on the run’ I tell them: “Don’t eat on the run!” A better strategy is to allow yourself to be active and then when you stop, actually stop, and prepare a wholesome meal (or have one ready to go) and then sit down, relax, eat it, and enjoy.
The take-home message for frequency is a simple one. If you are eating natural, whole foods, you should eat when you are hungry, until you are full, and then eat again when you’re hungry. If you occasionally miss a meal don’t stress about it at all.