Intermittent fasting, or IFing, is a very popular strategy for stimulating healing, increasing longevity, balancing hormones, increasing energy and mental clarity and losing weight. If you’ve heard this term bantered around Paleo circles and have been wondering what it’s all about, then wonder no longer!
How does Intermittent Fasting work? Intermittent fasting provides a variety of health benefits, predominantly due to stimulating a process call autophagy. Autophagy is the process by which a starving cell can reallocate nutrients from cell machinery that is not working optimally to fuel more essential cell processes. The cell degrades its own components, including damaged organelles, cell membranes and proteins, in a tightly regulated process. Autophagy can destroy viruses and bacteria within the cell that are resistant to other ways a cell might destroy them. It can even help the cell identify a viral infection that may have otherwise gone undetected. Autophagy plays a crucial role in immunity and inflammation, balancing the beneficial and detrimental effects of immunity and inflammation, and thereby may protect against infectious, autoimmune and inflammatory diseases. It may even prevent cells from becoming cancerous. Autophagy plays a normal part in cell growth, development, and homeostasis, helping to maintain a balance between the synthesis, degradation, and subsequent recycling of cellular products. In fact, failure of autophagy is thought to be one of the main reasons for the accumulation of cell damage and aging. Turning on autophagy is extremely beneficial (whether it’s turned on by intermittent fasting, exercise, ketosis, or straight calorie-restriction). The result is healthier, more efficient cells, which means a healthier, more efficient body.
What are the benefits of Intermittent Fasting? The benefits of intermittent fasting can be inferred from the effects of autophagy. However, more and more scientific studies are being conducted to confirm the effects of Intermittent Fasting and also isolate the optimal strategy for putting it into practice. Many of the benefits listed below have not been directly tested in humans using Intermittent Fasting; however, there is either strong evidence from animal studies or evidence from studies of autophagy itself, combined with anecdotal evidence to support these claims. The benefits of Intermittent Fasting include:
- Increasing lifespan.
- Increasing insulin sensitivity, which has many health benefits in and of itself. Of interest, the resulting increase in insulin signaling in the brain is thought to be how fasting/calorie restriction works to increase lifespan.
- Lowering blood lipids, triglycerides and other markers of metabolic syndrome.
- Fighting/preventing cancer. There is also some evidence that fasting before chemotherapy treatments can help reduce the negative side effects.
- Increasing growth hormone secretion (which builds muscle and burns fat).
- Normalizing expression of the hunger hormone ghrelin, thereby reducing appetite.
- Promoting brain and peripheral nervous system health by increasing neuronal plasticity and promoting neurogenesis, which has a large variety of effects such as boosting mood, memory, and mental clarity.
- Increasing dopamine production, thereby boosting mood and increasing anticipation and response to rewards (meaning we get more enjoyment from less food).
- Increasing energy through regulating metabolic hormones.
Intermittent Fasting is a little like hitting a reset button. It can help curb sugar cravings, restore energy, and even promote deeper sleep.
How do you do it? And how often? There are many options, but in general fasting for at least 16 hours is required to receive any benefits. Fasting beyond 24 hours doesn’t extend those benefits. So consider a fast anywhere between 16 and 24 hours. This includes sleep time, so a great way to intermittently fast is to simply skip breakfast. Ideally, that also means skipping your morning coffee. Drinking water is okay. Expect to feel hungry when you fast. This is different than simply listening to your body’s cues and waiting until you are hungry to eat (although many people are opportunistic about when they fast and simply choose days when they aren’t that hungry anyway). If you want to fast for 24 hours, you can skip breakfast and lunch. In terms of frequency, it is perfectly safe to fast 2 or 3 times per week (in the absence of health conditions that might complicate matters). If you prefer a longer fast, then once or twice per week is fine. Some people opt to have an 8-hour feeding window every day (see Leangains). However, I would argue that a daily fast is no longer intermittent. The body is able to adapt and predict the fast and many of the benefits are dulled. I also want to point out that you can benefit from fasting even if you do it very infrequently. Perhaps you only want to fast once per month, or once every few months. There is no clear evidence that fasting frequently will dramatically improve your health. Try it, see how you feel, see how you feel when you try it the next time, and then decide what is best for you.
What should you break fast with? When you are ready to eat, eat a balanced meal with lots of great protein and tons of veggies. You probably won’t feel very good if you eat too many carbs, so I urge caution with starchy vegetables and fruit. And don’t overdo the quantity you eat; try and aim for a normal meal (or only slightly larger than normal). I actually found in my own experimentation that I wasn’t that hungry and would eat an unusually small meal to break fast (I would then have more appetite for the meal after that).
Is fasting for everyone? The answer to this is a resounding NO! If you are not getting enough sleep or if your stress is not well managed, you may experience exaggeratedly high cortisol production in response to fasting, which can be detrimental. If you have a history of metabolic derangement or adrenal fatigue, I urge caution for the same cortisol-spiking reason. Women may be more likely than men to have an exaggerated cortisol spike in response to fasting (here‘s a great post reviewing women-specific responses to fasting). If you are not currently eating a fairly low carbohydrate diet (say, less than 100g per day), then fasting may have some side effects that mask the benefits (like headaches, fatigue, and nausea, caused by high cortisol). If you have any grains or dairy in your diet, you may experience a withdrawal-like effect because you aren’t consuming the opiate-like substances found in those foods. If fasting does not feel good, then don’t do it. If fasting feels good the first few times, but then stops feeling good, then stop. My own personal experience with intermittent fasting led me to realize that I can only get away with doing a 16-hour fast once or twice per month. Any more frequently and the cortisol spike stops weight loss, wrecks my sleep, and makes the whole experience completely pointless.