Intermittent fasting can work sometimes with exercise, depending on what you do and how.
You should avoid intermittent fasting if you work out in the morning.
The more training you’re doing, the less likely it’s a good idea.
Most of those who practice intermittent fasting and train effectively only strength train as their only meaningful, intense exercise. Generally, their only aerobic training is whatever walking they do during the day, or very brief high intensity interval training… if they do any cardio at all.
If you don’t do much exercise at all, then yes intermittent fasting is a good idea. And you should probably get some exercise, but intermittent fasting is a good habit.
A General Overview of Intermittent Fasting:
Instead of traditional fasting, where you may go a day or more without eating… intermittent fasting is about eating all your day’s meals in a short window of time and not eating the rest of the day.
Even if you eat a similar number of calories, the long break from eating gives your body an extended metabolic break, which can help reduce inflammation and better promote healing and recovery. This is actually more of the benefit of intermittent fasting than the potential fat burning improvements that can occur during the fast.
There’s no calorie restriction on how much you eat during the food window. But, obviously, it’s going to be harder to overeat in a single 8 hour window than it would be if you ate meals throughout the day.
Still, it is possible to outeat the fast during the 8 hour window and still maintain or gain weight. The fast doesn’t cause you to lose weight in itself. While it’s obviously more difficult in a shorter window of time, you can still overeat. That said, intermittent fasting can help with food portion and weight control.
I’m currently working in a fairly isolated location across town, and some weeks I’m working longer than 8 hours. My schedule many workdays is wall to wall booked:
Wake up
Perhaps run as time allows
Prep for work
Go to work and work 8-10 hours
Commute home
Work out if I didn’t get to in the morning
Eat dinner
Prep food and clothes for tomorrow
Go to bed.
On many workdays I can’t leave the client facility because I only have 30 minutes for lunch, plus even when I can the best food options are halfway across town. In this location there’s no supermarkets or viable restaurant options nearby. I won’t eat garbage fast food or something off a vending machine or convenience store counter. Even if any of it was satisfying (hint: doubtful), the near total lack of useful nutrients will crash my energy levels in the afternoon, in a job where I need to stay engaged and proactive.
And, of course, I’m now endurance training. I need to stay fueled for those morning and/or afternoon runs. I can’t just eat a minimal diet or whatever happens to be available and expect to perform as needed in these workouts. Plus, I have to maintain my overall health and not make choices that will contribute to illness or burnout. The food I eat has to support not just my general day to day health but what I am doing in training.
Most people who take vitamin supplements take them all at once, usually at the end of the day after their last meal.
Other than the risk of overloading your digestive tract and most of them being passed instead of used, this isn’t a bad strategy… especially if your vitamins are fat-soluble and you’ve had a large, fairly-fat-rich meal for dinner. Sure, some will likely get passed, but much of what doesn’t directly go to your bloodstream for use could them get stored in whatever fat you end up storing, to be released in your bloodstream later when that fat is tapped for energy. (This in fact is why vitamin capsules contain oils: The oils are digested and stored as fat, and the vitamins absorbed can come along for the ride.)
This is beneficial for runners, triathletes and other endurance athletes. When they go to train soon thereafter, any of that fat that’s aerobically burned will also release those stored vitamins for use… at a time when their body may actually need it.
Now, that said, while I’ve talked about vitamins that can and should go together (like Vitamin K2 and calcium), some nutrients don’t go with other nutrients. And one key nutrient to keep in mind is L-theanine.
There’s a lot I could say about fat burning, and there’s a legion of users-guide material throughout the internet world about methods to healthy fat burning (and many more about unhealthy fat burning ideas, which I will not bother to cover). I could write a piece about a dozen topics.
But I think it would help you to get some actionable tips in one place, and perhaps a shorter bit of writing on each of those in one place may help you more in the present. I can always cover all of these topics in additional pieces later.
So instead, I’m going to put a dozen topics into this long post, and succinctly get into why you should make it a standard or best practice.
If you’re trying to burn fat and struggling with it, these tips should help spur things along or keep things moving in the right direction.
One observation from my Garmin watch is that my stress score goes up after meals. No matter what I eat, how healthy the food I’m eating, my stress levels go up after the meal and stay elevated for at least a couple hours or longer, depending of course on activity and whatever else I’m doing. This is even true if I eat before bed: My stress levels can remain high for up to 2 hours after I drift off to sleep, following a relatively late meal.
My body only shows as resting (meaning a low stress score) in the morning if I have yet to eat breakfast. Despite any hunger pangs, it’s less stressful for me (according to heart rate variability) to be hungry than it is for me to digest a meal after eating. I find I record more restful periods when I intermittent-fast, aka skip breakfast and eat my first meal in the afternoon. Even with the added stimulus of coffee, my stress levels remain in a low resting state.
Garmin’s stress score is a function of heart rate variability, which can indicate activation or rest of your body’s sympathetic nervous system, which activates the body for activity. When the sympathetic nervous system is regularly activated, that indicates your body is under stress. A heart rate that does not vary much is indicative of the sympathetic nervous system being activated.
What does this have to do with eating? The sympathetic nervous system is a component of the autonomic nervous system, which passively operates our organs and hormonal glands. When you eat food, the autonomic/sympathetic nervous system begins diverting blood from other organs to the stomach and other relevant digestive organs to digest your ingested food. This activation of your sympathetic nervous system will continue until your food has been suitably digested and absorbed.
Even if you are laying down and doing absolutely nothing, your sympathetic nervous system during digestion is at work and therefore your heart rate variability at rest is likely small enough to indicate a level of stress to your Garmin. That doesn’t seem fair, but welcome to human biology.
If you live a relatively low-stress existence, eat only 2-3 meals a day, and you’re in good health, this is likely not a big deal. Your heart rate will eventually return to normal variability in a couple hours, and your resting time will read to your tracker as being at rest.
Of course, the vast majority of humanity doesn’t fall into the very thin demographic I just outlined. Most of us deal with some substantial degree of regular stress. Many of us have different meal habits, and many snack or eat enough meals a day that their bodies are digesting food not just throughout the entire day but even after going to sleep. And, of course, most people are not in optimal health.
This never minds people who endurance train, and are already subjecting their bodies to substantial stress through their training. The irony is that, depending on their eating habits, their fueling after workouts may in fact be contributing to their overall (already high) stress levels.
Science incidentally hasn’t laid a hand on this subject in over a decade, so we don’t have a ton of data on why this needs to be a stress reaction let alone if we can change the body’s sympathetic nervous reaction to eating food. So we have to accept that this is reality and work within that.
This incidentally is an underlying reason why intermittent fasting and the old “eat dinner like a pauper” rule* works so well. Fasting by skipping breakfast leads to generally lower stress levels, which improves overall hormonal function. Eating light limits the stress affect on your sleep time, which can improve the quality of that sleep.
Of course, this should not be taken as license to starve yourself and not eat at all. At some points during the day you do need to eventually take in quality nutrition and “take the sack” (so to speak) on the resulting sympathetic stress, because your body needs that nutrition.
This merely points out how the timing of that nutrition can affect your overall sympathetic stress, which in turn can affect your overall health.
Though this was never an intent of the rule, this is one benefit to making sure to eat quality protein/carbs as soon after a hard workout as possible, e.g. the 30 minute and 2 hour windows. Your body undergoes a similar sympathetic stress response after a workout, though the stress ripple effect can last longer than your meals (often, for example, a long run leaves you in a high stress state for the entire rest of the day, even if you spend all day laying down).
Eating as soon as possible and triggering that sympathetic nervous reaction can effectively piggy-back off the other sympathetic nervous reaction recovering from the workout itself. Eating much later could effectively re-start the sympathetic stress reaction, whereas eating right after one has began saves you the trouble of an extra stress reaction, or an extended period of elevated sympathetic stress. You can get back to a normal resting state more quickly, and spend more time in that low-stress rested state than if you had eaten later and had two separate stress-creating episodes for your sympathetic nervous system.
This lends credence to the following ideas:
Unless you work out in the morning, or you have health-related reasons not to do so, it’s probably best to intermittent fast by skipping breakfast, nothing but coffee and water.
Probably only eat breakfast if doing a morning workout, and probably following that workout.
It’s important to consume nutrition within 30 minutes of finishing tougher workouts, and to eat a meal within two hours of finishing those workouts.
Regardless of the size of dinner, you want to buffer a couple of hours between the end of dinner and bedtime, to allow digestion and its stress reaction to finish as early in the sleep cycle as possible.
Avoid snacking, as it restarts the sympathetic nervous stress reaction. Eat full meals and only full meals, 2-4 times a day.
The below is a scenario I’m working through now that I’m in town, and a great example of the thought process required to maintain my exercise and training progress, as well as stabilize my diet while on the road long-term.
Currently I’m working the swing (aka 2nd or evening) shift on assignment. On the one hand this allows a lot of time in the morning to run or exercise. I ran a very comfortable 4.3 miler near my lodging around 10am on Wednesday.
But my assignment also requires I spend a lot of time on my feet walking the facility, and on that Wednesday I burned about 4000 calories that day.
Never minding how tired I felt at the end of the day… while not opposed to burning some fat after bulking up in Vegas, I also was worried I wouldn’t consume enough food (especially protein) to prevent muscle catabolization. I ate a solid pre-work meal, a light snack during work and then a ridiculously large processed meal before going to bed. Despite housing 3300 claories I was well below my overall burn.
Yesterday I decided to not exercise at all, just work that day, to see how much I burned. After a similar workday of activity, I ended up finishing yesterday with 3840 calories burned. I had done nothing physically but walk a facility floor over an 8-9 hour day. On a similar eating schedule I *only* managed 2900 calories, and of course still finished well short of my overall burn.
While not a bad dilemma for someone trying to burn fat, this still presents a dilemma.
The Loyola Ramblers men’s basketball team begins their season tonight with an exhibition game. I have season tickets and I go to pretty much every single game I can for both the men’s and women’s teams.
Over the last couple months I had found a rhythm with cooking dinner on weeknights that suited me fairly well. I’d often return home from work and running either around 6:00-7:00 pm, or after a racing team workout a bit after 8:00pm. I would spend an hour preparing my typical meal, usually baked chicken with either baked/boiled potatoes, or boiled pasta.
However, the start of Loyola’s season poses a clear problem on weeknights. With these games starting at 7-8pm, lasting around a couple hours, followed by a not terribly long train commute home… I walk in the door sometime around 9-10pm.
I like to get to bed before 11pm at the latest, and obviously coming home at 9-10pm doesn’t allow much time to cook dinner before 11pm. Staying up late just to cook a decent meal is not workable. The conventional meal plan isn’t going to work.
I don’t want to buy a ready-to-eat or easy-to-bake $7-12 meal on the way home after every game, because that gets expensive in a hurry, and most workable options are not the most nutritious. Plus, it’s likely I’m already going to need to buy something to eat after leaving work, before the games. I can’t go 8-10 hours without a meal.
Of course, I also don’t want to rely on eating arena food during the game for the same reasons.
I also don’t want to rely on some sort of snack food, which in my experience doesn’t really satisfy, which poses a huge problem overnight as I tend to wake up overnight when hungry.
I also don’t want to prepare a meal in advance and then re-heat it in the microwave when getting home. Never minding the lacking quality of such a meal, microwaving can sap or zap various nutrients, plus materials from the plating can leech into the food. I avoid microwaving food in general.
So… what to do? Going entirely without is not a workable option while running regularly. I’m not going to just miss games to get my meals in, of course. There has to be a way to make this work.
And it turns out there is.
Recently I bought an egg cooker device at Target. I once had a Cuisinart Egg Cooker in Seattle (that I had to dump once I moved to Chicago), and it worked quite well with making steam-poached eggs. It turns out this cheaper Copper Plate model does just as well, steaming two eggs at a time in a few minutes.
I had been eating steam-poached eggs as a snack, but it’s entirely possible to steam them and eat them as the protein portion of a dinner.
While I could prepare rice in my Aroma Automated Cooker to be ready when I return home… a more nutritious solution would be to boil about 400 calories of pasta, and also heat some marinara sauce to eat with it. Combine the eggs, the pasta and the sauce, and that’s a decent post-game meal, in less than 20 minutes.
It certainly beats paying for a sandwich or a burrito every time I come home for a game.
This is one of many possible examples of the meal planning my training requires. You can’t cut corners with nutrition any more than you can cut corners with your training
A lot of people, when life intervenes, elect to either cut life and focus too much on their training, or to skimp on meal planning only for their development and health to suffer in kind.
But with some advance effort you can totally find workable solutions that avoid having to cut corners in any way.
