I think my own experience with Intermittent Fasting was similar to a lot of other folks, because the initial thing that attracted me to it was that it seemed like an ideal way to combat hunger on a diet: by compressing your calories into a smaller feeding window, you can feel more satisfied. This is all I was really after when I began, and IF certainly delivered that; it made cutting easier due to increased satiety. As a bonus, it also taught me to manage and control my own hunger. There was an immense psychological benefit to be had there; the fasting period teaches you that being hungry is not a disaster, nothing bad will happen. But that’s not what this post is about.
I wanted to write about what I’ve been experiencing in my second phase of adopting more of the LeanGains protocol, which is calorie and carb cycling between training and rest days. The idea with this part of LeanGains is to eat more on training days when our body wants more calories to grow, and less on rest days, when we can hopefully switch over into fat burning. This is sometimes called a “recomp”, because we are trying to lose fat and gain muscle at the same time. This is a contentious idea in bodybuilding circles, with many claiming that when you chase two birds, you usually end up coming home with none. These folks are generally in favor of more traditional cut and bulk cycles. While I agree with the opinion that cutting and bulking is indeed more time-efficient overall, I think that a recomp may be a valid goal for some people, and IF offers an intriguing way of going about it.
To do a recomp using IF, you must first establish a training schedule. Martin Berkhan (the very smart man behind LeanGains.com) advises training three days a week, either with a beginner’s whole body routine (like Starting Strength) or an intermediate Reverse Pyramid Training scheme (RPT). Regardless of which you do, let’s say you choose to train Mon/Wed/Fri.
Then you need to pick a calorie cycling scheme. The most commonly used scheme is a -20% caloric intake on rest days and a +20% caloric intake on training days. For those not gifted with the math, training 3 days a week like this would put you in a very slight net caloric deficit for the week. This is pretty much maintenance, since this small number is well within the margin of error in terms of estimating calories burned and calories eaten. If you wanted to place more of an emphasis on fat loss, you could do something like -30% and -10%, or to emphasize more of a bulking approach, -10%/+30%. There’s a handy calculator to play with this here. For the rest of this post though, I’m going to assume we’re going for a middle of the road recomp.
By the way, I am going to assume anyone reading this has already worked out their maintenance calorie intake, as well as their target minimums for protein and dietary fat. If you haven’t, you should probably get that done or the rest of this post won’t make much sense to you.
First, let me say that protein should be kept consistently high on both training and rest days, which leaves fat as the one remaining macro to be reduced in favor of additional carbs on training days.
So finally, we get to the carb cycling part then. Carb cycling itself is nothing new, nor is the application of it within the IF protocol. All we’re doing here is eating high carb on training days and low carb on rest days, which bodybuilders have been doing for a long time. This is easier to do within our overall calorie cycling scheme, since we have way more room for carbs on our +20% training days.
OK, simple enough. But, uh, why are we doing it? Well, let’s look at a few of the supposed effects and benefits this is trying to achieve for us:
- Eating additional calories on training days attempts to make more calories available to the body when we can actually make use of it to build muscle. Hopefully we are less likely to store it as fat on these days. Ideally, the bulk of the caloric intake should be post workout, or at least around the time of the workout. This is trying to take advantage of the post-workout anabolic window. No, not the broscience-based “must eat immediately from my tupperware in the locker room or all gains are lost window”, but the much wider 24 hour anabolic window that will persist well into the next day. Note that this is not a make or break thing; we’re just trying to move calories closer to training, hoping for a more favorable anabolic response.
- Getting our extra calories from carbs on training days uses carbs to refill our muscle glycogen stores, and gives us extra energy for more effective workouts.
- Some folks would also argue that the increased insulin response from the high carb day is going to promote additional muscle protein synthesis and make us more anabolic that day. The evidence is not strong in supporting this notion however, with the counter argument being that normal pre-workout nutrition has already provided more than enough insulin for a maximal anabolic response, and that shooting for more of a “spike” has no net effect. While this appears to be true, the variable that may yet make this a valid notion is the fact that we are training fasted, with no preworkout nutrition in play. Is there an increased anabolic response from an insulin spike after training in a fasted state? This is unclear, but it’s part of what fasted trainees are hoping for.
- By eating low-carb on rest days, we are keeping insulin levels low, which may help to make us more insulin-sensitive. This may further increase the anabolic response the next day to training and a subsequent high carb intake, leading to a sort of “anabolic rebound”. Truth be told, this is a bit of speculation based on a potentially shaky chain of logic. There is some evidence favoring improved insulin sensitivity from IF, but whether this leads to a more anabolic response the next day is not clear.
- Low carb rest days also allows for increased fat intake on those days, which helps us meet our minimum targets for dietary fat. Eating low carb with most of our calories coming from protein and fat is particularly satiating, which is very beneficial since we are in a -20% caloric deficit that day.
- Lower carbs on rest days may also promote additional fat burning based on the idea that insulin is anti-lipolytic, and that low insulin levels will remove the “brakes” on fat oxidation during our rest day. This is another hotly debated notion, with evidence on both sides of the argument, and is straying into the whole notion of whether or not a calorie is a calorie, and if there is any benefit to low carb diets in the first place. For the optimists among us, here’s some of the research favoring this idea. And for the pessimists, check this out.
- The other side of the fat loss coin is that with high carbs and low fat on training days, we are looking for more favorable “calorie partitioning” towards muscle building instead of fat storage. In a caloric excess, at a time when protein synthesis is high and muscle glycogen is at least somewhat depleted, the body is hopefully going to be favoring use of the energy from those carbs for building new tissue.
- Dietary fat is also kept low on training days because (as Lyle McDonald teaches us) in the presence of high carbohydrates, the body is predisposed to store dietary fat. Fat is not useful for muscle protein synthesis, so all we want is to meet recommended minimums on training days.
- Dietary fat is high on rest days because we are in a caloric deficit; there is going to be no net increase in fat stores on these days, so we’re fine there.
- Unlike a traditional long term caloric restriction, carb cycling eliminates problems with cravings and such due to depressed levels of leptin. This means there is no requirement to try and manage leptin (and the weird cravings it causes us) through refeeds and diet breaks.
- Although we are pretty much eating at maintenance levels if you add up all the calories for a weekly total, the effects of more favorable calorie partitioning are hopefully such that our training days are shuttling calories into muscle growth, leaving fewer excess calories available to be stored as fat. The idea here is that we’ve nudged more of our weekly caloric intake towards muscle building and away from fat storage, because on rest days we are in a caloric deficit and net fat stores will decrease.
- Finally, carb cycling may have an interesting effect on plateaus. Because we are not continuously restricting intake over a long period of time, the typical response the body has to reduced calories and carbs (retaining water), is less likely to happen. Also, cortisol (the other culprit behind water retention) is less likely to be chronically elevated. Yes, we will experience more short term water balance fluctuations between training and rest days, but this longer term “hold” on retained water, the one that masks fat loss and causes a perceived “plateau”, is less likely to be an issue. Psychologically this makes compliance and tracking less of a head-game. Unfortunately I’ve no evidence to support this; it’s just based on my own potentially faulty chain of logic and anecdotal evidence from people reporting the effect.
Basically we have a series of many different effects at work here, hopefully ones that work together in a way that maximizes fat loss and muscle gain at the same time. There is unfortunately a lack of good studies done on fasted training, intermittent fasting in general, and on calorie partitioning, so I don’t know if any of these benefits will prove out in the long run. But in the meantime, people are at least having a lot of anecdotal success with this style of “recomp”. And if nothing else, it’s a damn enjoyable way to eat.