5 intermittent fasting schedules (And how to pick)
From the desk of Robb Wolf
<p><span style="font-weight: 400">I started writing about intermittent fasting in 2005. As I saw it, following a periodic fasting schedule was a valuable way for folks to pump the brakes on over-indulgent eating habits. Eat less frequently and you naturally consume less food. Eat less food in a shorter window and—especially for those with obesity and diabetes—your metabolic health can shift toward the better. It made sense to me.</span></p><p><span style="font-weight: 400">It still makes sense, but I’m no longer one of the few people writing about it. A chorus of voices has arisen to serve the public’s growing interest in </span><a href="https://drinklmnt.com/blogs/health/benefits-of-fasting" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">fasting</span></a><span style="font-weight: 400">. Unfortunately, many of these sources portray fasting as a panacea for all people all the time. Let’s be clear: Intermittent fasting isn’t always beneficial. The longer-duration fasting schedules, in particular, have the potential to do more harm than good, especially when practiced by lean, metabolically healthy people.</span></p><p><span style="font-weight: 400">While folks embark on fasting for a variety of reasons, one of the largest draws involves the notion that fasting will forestall aging and prevent cancer. People think these results are driven by the suppression of various growth-promoting signals, including mTOR and insulin-like growth factors (IGF’s). There’s a lot of misguided thinking around this topic that fuels our tendency to focus on less likely risks.</span></p><p><span style="font-weight: 400">Meanwhile, folks ignore guaranteed issues like sarcopenia, the loss of muscle mass as we age. Sarcopenia is a guaranteed process with highly predictable parameters, and we can prevent its effects by strength training and eating adequate protein. To that last point, is it possible to absorb enough protein in one daily meal to maintain muscle? </span><a href="https://drinklmnt.com/blogs/health/should-you-train-fasted-benefits-downsides-and-when-to-do-it" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">I’m not sure</span></a><span style="font-weight: 400">. And at the least I think eating one meal per day is far from optimal for muscle mass maintenance.</span></p><p><span style="font-weight: 400">What about the already-lean person? Should they abstain from calories every other day via alternate day fasting? I don’t think so. Eat enough meals per day to stay lean and strong. Then drop in a bit of fasting or time restricted eating if it helps you perform better.</span></p><p><span style="font-weight: 400">Essentially, more is not always more. That’s a taste of my fasting philosophy. What follows is the four-course meal. You’ll learn how intermittent fasting works, the benefits of intermittent fasting, five fasting protocols, and three criteria to decide which protocol to choose. By the end, you’ll be in an excellent position to choose the intermittent fasting schedule that works best for you.</span></p><h2><b>Intermittent Fasting 101</b></h2><p><span style="font-weight: 400">I define </span><a href="https://drinklmnt.com/blogs/health/intermittent-fasting-a-science-based-guide" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">intermittent fasting</span></a><span style="font-weight: 400"> as scheduled breaks in caloric consumption of between 12 to 36 hours. Extended fasting is when the breaks exceed 36 hours.</span></p><p><span style="font-weight: 400">What do I mean by “breaks in caloric consumption”? I mean consuming significantly fewer calories than one would typically consume. For instance, eating 0 to 500 calories in one 24-hour period, then eating 2000 calories in the next 24-hour period.</span></p><p><span style="font-weight: 400">Wait, doesn’t fasting have to be a zero calorie affair? Not necessarily. The </span><a href="https://www.cureus.com/articles/12903-intermittent-fasting-the-choice-for-a-healthier-lifestyle#:~:text=Alternate%20day%20fasting-,A%20%E2%80%9Cfast%20day%E2%80%9D%20where%20individuals%20consume%2025%25%20of%20energy,following%20a%20%E2%80%9Cfast%E2%80%9D%20day.&text=Daily%20energy%20intake%20of%20450,ordinary%20food%20was%20gradually%20introduced." target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">research</span></a><span style="font-weight: 400"> suggests that the benefits of fasting—weight loss, metabolic improvements, etc.—still result if a person consumes less than 25% of total daily calories during the fasting interval. And similarly, there </span><i><span style="font-weight: 400">are</span></i><span style="font-weight: 400"> benefits to calorie restriction between 5-10% below calorie expenditure. Most reputable weight loss approaches within the last 100 years have functioned this way.</span></p><p><span style="font-weight: 400">My position is that, whether we fast or just figure out a way to spontaneously reduce calorie intake (i.e. higher protein diets are great for satiety), the end result is largely the same.</span></p><p><span style="font-weight: 400">Some fasting schedules entail fasting on certain days of the week, while others entail fasting for a certain amount of time every day. The weekly schedules allow limited calories on fasting days, while the daily schedules do not.</span></p><h2><b>The Machinery of Fasting</b></h2><p><span style="font-weight: 400">You don’t need any special tools to start fasting. You already have everything you need.</span></p><p><span style="font-weight: 400">Like us, our ancestors were well-adapted to temporary calorie restriction. They had body fat—a storehouse of latent energy, thousands of calories strong—ready to be burned during times of scarcity.</span></p><p><span style="font-weight: 400">As a byproduct of this fat burning, their livers produced molecules called ketones to fuel their hungry brains. Being in </span><a href="https://drinklmnt.com/blogs/health/the-best-diet-for-ketosis" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">ketosis</span></a><span style="font-weight: 400"> helped them stay sharp and therefore helped them survive.</span></p><p><span style="font-weight: 400">All this machinery remains today. We still burn fat during a fast. We still produce ketones. We still get that mental edge in a reduced-calorie state. But since fasting is no longer a Darwinian necessity, most people don’t do it.</span></p><p><span style="font-weight: 400">Instead, most people spend the greater part of the day (and night) munching, nibbling, and grazing. That’s another aspect of our genetic programming: see food, eat food. That instinct kept cavemen alive. However, in times of plenty, that same heuristic becomes maladaptive. We overindulge (</span><a href="https://drinklmnt.com/blogs/health/how-sugar-is-making-us-sick" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">especially on sweets</span></a><span style="font-weight: 400">), and we succumb to obesity, diabetes, and chronic disease.</span></p><p><span style="font-weight: 400">Intermittent fasting is a deliberate practice that prevents overeating. Most of its benefits, I believe, follow from this point. And let me be clear about this: if you are lean and metabolically healthy, I’m not sure there is much (if any) benefit to intermittent fasting other than that it may simplify your life (cooking fewer meals per day) or serving as THE tool that helps you avoid overeating.</span></p><h2><b>Benefits of Intermittent Fasting</b></h2><p><span style="font-weight: 400">The biggest reason people fast is to lose weight. It’s the big selling point. There’s compelling </span><a href="https://www.cureus.com/articles/12903-intermittent-fasting-the-choice-for-a-healthier-lifestyle" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">evidence</span></a><span style="font-weight: 400"> that people lose weight on various intermittent fasting schedules.</span></p><p><span style="font-weight: 400">It makes sense: If you compress your feeding window, you’ll naturally consume fewer calories. And when you consume fewer calories than you expend, you lose weight.</span></p><p><span style="font-weight: 400">Also, being in a ketogenic state </span><a href="https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4313585/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">helps</span></a><span style="font-weight: 400"> with appetite management. And ketosis has </span><a href="https://drinklmnt.com/blogs/health/how-to-get-into-ketosis" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">other benefits</span></a><span style="font-weight: 400"> related to inflammation, mental health, and energy levels. But you don’t need ketosis to explain fasting-related weight loss.</span></p><p><span style="font-weight: 400">Beyond weight loss, I group the benefits of fasting into two buckets:</span></p><ol><li style="font-weight: 400"><span style="font-weight: 400">Metabolic benefits</span></li><li style="font-weight: 400"><span style="font-weight: 400">Circadian rhythm benefits</span></li></ol><p><span style="font-weight: 400">By metabolic benefits, I mean the benefits for blood sugar regulation and fat metabolism. (Lower blood sugar, lower insulin, increased fat burning.) And when you look at the </span><a href="https://pubmed.ncbi.nlm.nih.gov/30646030/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">evidence</span></a><span style="font-weight: 400">, intermittent fasting looks to be a </span><a href="https://drinklmnt.com/blogs/health/can-intermittent-fasting-help-reverse-type-2-diabetes" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">promising therapy for type 2 diabetes</span></a><span style="font-weight: 400">.</span></p><p><span style="font-weight: 400">The circadian rhythm benefits are crucial too. By fasting overnight, you </span><a href="https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7262456/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">promote</span></a><span style="font-weight: 400"> the conditions necessary for restful sleep. Why? Because food (like light) activates the part of your brain that controls your metabolism, appetite, sleep cycles, and more. Food during the day wakes you up, fasting at night shuts you down.</span></p><h2><b>5 Intermittent Fasting Schedules</b></h2><p><span style="font-weight: 400">Here I’ll review the five most common fasting schedules, starting with daily programs—my preference—and ending with weekly programs.</span></p><h3><b>#1: 12/12 (Overnight fasting)</b></h3><p><span style="font-weight: 400">Overnight fasting is the simplest form of time-restricted feeding (TRF). TRF is a species of intermittent fasting that entails compressing your daily feeding window to 12 hours or fewer. The research </span><a href="https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7262456/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">suggests</span></a><span style="font-weight: 400"> that TRF provides metabolic and circadian benefits across many populations.</span></p><p><span style="font-weight: 400">If you’re new to intermittent fasting, 12/12 fasting is the ideal place to start. Go between dinner and breakfast without munching (12 hours between meals) and you’ll reap the rewards.</span></p><h3><b>#2: 16/8</b></h3><p><span style="font-weight: 400">16/8 is the next level of time-restricted feeding. It entails eating all your daily calories within an 8-hour window each day.</span></p><p><span style="font-weight: 400">There’s no need to consciously restrict calories on 16/8. Rather, you may want to consciously </span><i><span style="font-weight: 400">feast</span></i><span style="font-weight: 400"> to get enough nutrients (like protein) in the compressed window.</span></p><p><span style="font-weight: 400">When calories are held constant, the research </span><a href="https://pubmed.ncbi.nlm.nih.gov/27737674/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">suggests</span></a><span style="font-weight: 400"> 16/8 is perfectly compatible with fat loss and muscle maintenance. Skipping breakfast is also compatible with enhanced productivity.</span></p><p><span style="font-weight: 400">In case you were wondering, I practice something like 16/8. It’s just enough fasting to keep me lean and just enough feeding to keep me energized. I tend to front load more calories early in the day and make my dinner a lighter meal, but that’s all preference.</span></p><h3><b>#3: OMAD</b></h3><p><span style="font-weight: 400">When you practice OMAD, you eat “One Meal a Day.” All of your calories come from that single feeding.</span></p><p><span style="font-weight: 400">In one </span><a href="https://pubmed.ncbi.nlm.nih.gov/17413096/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">study</span></a><span style="font-weight: 400">, normal-weight people doing OMAD </span><i><span style="font-weight: 400">did</span></i><span style="font-weight: 400"> lose fat compared to 3-meal-per-day controls (calories between groups held constant) but they also showed elevations in blood pressure and LDL cholesterol. The “why” isn’t clear, but understand that fasting is a stressor for your body. More isn’t always better.</span></p><p><span style="font-weight: 400">Another issue I have with OMAD is that it often leads to unintentional calorie restriction. That’s okay for obese and type 2 diabetic folks, but I’m not crazy about it for people already at a healthy weight, especially not a hard-charging athlete. If you get super busy and can only fit in one meal that day, that’s okay. It shows you are metabolically flexible and resilient. But train hard and eat OMAD for a long period of time, and I can almost guarantee you’ll overtrain, lose muscle, lower performance, damage your hormonal function, and hurt your sleep.</span></p><p><span style="font-weight: 400">I’ve worked with a LOT of people in the 23 years I’ve been doing this. Back in the early 2000’s I was super excited about various forms of fasting for athletes. But it did not take me long to discover that aggressive fasting (like OMAD) could break an athlete in a spectacular way.</span></p><p><span style="font-weight: 400">I should also mention that for those with diabetes, it’s important that your fast is medically supervised. Always talk to your doc before diving headfirst into a program that will significantly affect your blood glucose levels.</span></p><h3><b>#4: 5:2</b></h3><p><span style="font-weight: 400">5:2 weekly fasting entails consuming 0-25% of normal calories on two non-consecutive days per week. For example, on a 2000-calorie diet, one would consume 0-500 calories on Monday and Thursday, and then 2000 calories on the other five days.</span></p><p><span style="font-weight: 400">Unsurprisingly, 5:2 can </span><a href="https://www.cureus.com/articles/12903-intermittent-fasting-the-choice-for-a-healthier-lifestyle" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">help</span></a><span style="font-weight: 400"> with weight loss. That’s what happens when you eat fewer calories overall. I could see a schedule like this working for </span><i><span style="font-weight: 400">some</span></i><span style="font-weight: 400"> athletes if, on lower calorie days, the meals are predominately protein (to help minimize muscle loss) and the training is of lower intensity.</span></p><h3><b>#5: ADF</b></h3><p><span style="font-weight: 400">Alternate-Day Fasting (ADF) is one of the most aggressive intermittent fasting schedules. You consume 0-25% of your regular calories every other day.</span></p><p><span style="font-weight: 400">ADF is often used for therapeutic purposes. For instance, it seems that ADF can have </span><a href="https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC7732631/" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">pretty profound</span></a><span style="font-weight: 400"> (and relatively rapid) effects for folks with obesity and diabetes (with medical supervision, of course).</span></p><p><span style="font-weight: 400">But it’s not easy. You’re asking folks to sacrifice three-to-four days per week to the fasting gods.</span></p><p><span style="font-weight: 400">ADF may be worth it as an attempt to kick diabetes, but I don’t recommend it for widespread use. The potential for muscle loss is too high, and the sustainability factor is too low.</span></p><h2><b>How To Pick a Fasting Schedule</b></h2><p><span style="font-weight: 400">To pick a fasting schedule, I suggest using three criteria:</span></p><ol><li style="font-weight: 400"><span style="font-weight: 400">Your schedule</span></li><li style="font-weight: 400"><span style="font-weight: 400">Your enjoyment</span></li><li style="font-weight: 400"><span style="font-weight: 400">Your goals</span></li></ol><p><span style="font-weight: 400">Let’s review how each can guide your decision-making framework.</span></p><h3><b>Your Schedule</b></h3><p><span style="font-weight: 400">How would you structure your perfect day? Your answer will inform your choice of fasting schedule.</span></p><p><span style="font-weight: 400">If you enjoy doing compositional work in the morning (as I do), you might </span><a href="https://drinklmnt.com/blogs/health/how-to-break-an-intermittent-fast-the-healthy-way" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">skip breakfast</span></a><span style="font-weight: 400"> and pursue 16/8. But if family breakfast is a sacrament, perhaps a simple overnight fast would work better.</span></p><p><span style="font-weight: 400">In general, the weekly fasting schedules are more disruptive than the daily schedules. It’s tough to find a rhythm when you’re fasting every other day. </span></p><h3><b>Your Enjoyment</b></h3><p><span style="font-weight: 400">I enjoy my fasting schedule tremendously. After 16 hours of fasting, that first meal back is a joy. Minimizing your meals can maximize your eating pleasure. </span></p><p><span style="font-weight: 400">Well, up to a point, that is. Intermittent fasting shouldn’t feel like a chore. Hunger is normal, but you shouldn’t feel irritable, cold, or tired. These are signs you’re fasting too aggressively. Back off to a shorter fast.</span></p><p><span style="font-weight: 400">Ideally, you should </span><i><span style="font-weight: 400">start </span></i><span style="font-weight: 400">with an overnight fast and work your way up the fasting ladder. Most folks tend to feel best in the 13 to 18-hour range. More is NOT inherently better. If you get overly hungry, just eat. There is no medal waiting for those who overdo their fast.</span></p><h3><b>Your Goals</b></h3><p><span style="font-weight: 400">Are you fasting to lose weight? For health and longevity? To keep muscle and lose fat? It’s up to you to decide what an appropriate goal is, but typically I see the latter.</span></p><p><span style="font-weight: 400">Knowing your goals helps you choose the appropriate fasting schedule. For example, more extended regimens are probably useful for weight loss, but not so great for muscle maintenance.</span></p><p><span style="font-weight: 400">I view weekly regimens like 5:2 and ADF as the power tools of the fasting tool shed. They’re useful for breaking through stubborn cases of obesity and type 2 diabetes, but too forceful for regular use.</span></p><p><span style="font-weight: 400">As you’ve probably noticed, I prefer daily regimens. And within those, I tend to prefer 12/12 or 16/8. They offer the benefits of intermittent fasting without acting as an excessive stressor on your body. Go beyond that, and you run the risk that your practice becomes unenjoyable or unsustainable.</span></p><p><span style="font-weight: 400">Sustainability is the key. And on that note, I’ll leave you with one last tip: when folks don’t dial in their electrolytes (specifically sodium) on a fasting regimen, they tend to feel like hell and quit. Check out my article on </span><a href="https://drinklmnt.com/blogs/health/electrolytes-while-fasting-benefits-and-best-sources" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">electrolytes and fasting</span></a><span style="font-weight: 400"> to learn more. (Hint: Drink </span><a href="https://drinklmnt.com/products/lmnt-recharge-variety-pack" target="_blank" rel="noopener noreferrer"><span style="font-weight: 400">LMNT</span></a><span style="font-weight: 400">, our tasty electrolyte drink mix that won’t break your fast.)</span></p><p><span style="font-weight: 400">To sum it all up, the trick is to find a schedule that slots nicely into your lifestyle. Once fasting becomes a habit, you won’t even need to think about it.</span></p>