Food to Fuel Exercise
There’s a lot of confusion about eating before exercise. Do all workouts need fuel before? Are some more worthy than others? What should I grab?
To begin, consider why you are engaging in physical activity – are you trying to help your body adapt and improve? Or are you moving to pursue weight loss? This distinction matters. One positions food and the body as a threat. The other as an ally.
“Training” is pursued in the spirit of adaptation – doing the types and amount of movement and nutrition to help the body move easier, farther, and/or faster with less effort. Training involves tough days, easy days, and rest with thoughtful progressions and the body’s challenge/recovery. It helps the heart beat more efficiently, lungs exchange oxygen, and muscles fire more reliably. It’s about improving movement and honoring/respecting the shape needed to perform that movement. Fueling from this perspective is focused on giving the body the nutrients it needs to perform and recover at its best.
VS
“Weight loss”, on the other hand, is about engaging in physical activity to expend energy consumed and/or break down the tissues of the body – both fat and lean tissue. It is often about moving regardless of how you feel, completing a specified routine, and doing it with the least amount of fuel possible. It does not necessarily result in adaptation to the heart, lungs, or muscles. I would argue that engaging in movement is pursuit of weight loss is oppositional to health. Often when people are thinking about food and weight loss the belief becomes, “eat the least amount possible to survive the necessary amount of movement.” Under-fueling the body can undermine many of the physiological benefits of movement.
Simply put, weight loss is about doing things TO the body. Whereas training is about thoughtful movement WITH the body.
Let’s remember the “point” of training
When you train, you are essentially trying to accomplish 2 things :
- Strength – be able to resist more force. Whether that means picking up your grandchild or a small pickup truck, strength training is about creating capacity within the muscle and allowing the body to practice key movements in a controlled setting
- Endurance – be able to move farther with less effort. Whether that’s being able to walk down the hall or complete an Ironman triathlon, you are strengthening your heart and lungs which thereby increases the amount of oxygen they can take in and circulate to the body, with less effort. It also creates more oxygen receptors in the muscles.
Both of these goals require you to…
- Challenge yourself (consistently). When you challenge (not destroy) yourself, you cause you cause little bits of microscopic damage to the part of the muscle that contracted (heart, lungs, biceps, etc). The harder the work (within reason), the more damage that occurs, and the greater the repair/adaptation – thereby building muscle. The body does a lot of this within the first hour of exercise and then continues for the next 24-48 hours. We refer to this time period as “recovery.” If you give your body energy before a workout (food = energy), you are able to work at a higher level thereby increasing the challenge.
- Help your body repair. Nutrition is helpful with this repair process. When you eat or drink protein (paired with a little carbohydrate and antioxidants) within an hour of the damage, the body does a better job repairing the damage and builds better/stronger muscle. This allows you to workout harder the next time, causing more damage…then repair/adaptation….and the process continues. If you give your body energy (food = energy) after a workout, it has more tools to repair the damage. Not eating after a workout is like asking a builder to fix a roof without a hammer or nail gun. Sure they can use other tools and “get by”, but the process will take longer and likely not be as strong compared to if they had the right tools. I’ll cover eating after movement in another blog post.
Questions:
Do I always need fuel before movement?
Generally, yes
Whether or not you really "need" a preworkout snack depends on the timing of your last meal, its composition, and how long you're planning to train.
If your last meal was 3+ hour prior, you would benefit from a snack.
If your last meal was 2-3 hours prior (and it had enough of the fuel you need...aka carb) a pre-workout snack becomes less crucial.
These aren't "rules" around when you should and should not have a preworkout snack. If you're hungry, doing doubles, have workouts over 90 minutes, and/or have higher energy needs, go for the snack! It will only benefit your ability to perform better.
What kind of fuel is best before - carb, protein, or fat?
Carbs!
ALL exercise uses energy from ATP. But our body's ability to quickly convert glucose, amino acids, or lipid into ATP varies depending on what we do. Very high intensity exercise primarily uses glucose (aka, blood sugar) as fuel. As exercise becomes longer/ lower intensity, the body uses more fat as fuel (but it also uses glucose for the process).
Most exercise (strength and cardio) uses glucose as fuel in one way or another. Glucose (aka blood sugar) comes from starch (rice, potato, pasta, crackers, cereal, flour, bread) and sugar. The body also has stores of glucose called glycogen that it will use if it runs out of glucose. And if we're out of glycogen at higher heart rates, the body will turn to amino acids. The body prefers to have glucose readily available rather than breaking down glycogen for fuel.
Note: The body also uses fat as fuel at lower intensities. BUT that doesn't mean you need to or should workout longer or slower in order to lose weight / burn fat. Changing your workout duration and intensity just to change fuel sources will either leave you under or over challenged. Do what you love and challenge your body - it will adapt as necessary.
How much do I need?
It depends
Generally, most bodies can tolerate 1g/kg of carbohydrate in the hour before physical activity. The carbohydrate source should be low in fiber, fat, and protein to avoid GI distress.
Why not protein / fat in the hour before a workout?
They're the wrong tool for the job...
Your stomach needs blood to digest foods - particularly proteins and fat. However when you're training, your muscles ALSO need more blood for fuel and cooling. This creates a challenge for the body - who gets the blood? As a result, people end up either feeling fatigued OR with a stomach ache, particularly if they're trying to workout at very high intensities OR in hot conditions. Examples of challenging foods may be - eggs, yogurt, milk, cheese, bacon, sausage, meats in general, cottage cheese. However, if you're working out at lower intensities (or have a stomach of steel), it's not as big of a consideration
But won't fiber prevent me from "crashing?" Isn't it "healthy?"
It's about function...
I'm not saying that these foods are "good" or "bad", but they are different tools for different times. Fiber has a lot of benefits, but eating it takes up a lot of room in the stomach and for some, can cause GI upset (particularly those working at high intensity/high heart rates). Additionally, foods with loads of fiber often aren't as energy dense so you have to eat a larger portion in order to get the fuel you need. So while a bowl of berries sounds like the "healthier" option, it would take almost 1 1/2 cups of berries to get the same energy from a slice of bread.
What about caffeine?
It has its place...
While caffeine is an ergogenic aid (aka, it reduces the perceived effort of workouts so you perform better - particularly for endurance activity), it has a bell curve. That means caffeine has been shown to improve performance in small doses, but quickly reduces performance if taken in excess. Additionally, too much caffeine easily cause diarrhea, increase you heart rate, make you jittery, dehydrate, and leave you exhausted. It can also interrupt your sleep quality if you're consuming it later in the day, which impairs recover. So a cup of coffee can be helpful before morning workouts, but more may reduce your performance.
So you're telling me to eat a lot of sugar before a workout?
Kind of...
Sugar and processed foods have their place in sports nutrition and performance. It is about understanding how our body navigates different types of chemistries. If we are in the final hour before a workout, we need nutrients that are readily available and easy to digest - that tends to be foods with more starch / sugar. But outside of that, our bodies can tolerate more complex experiences. The preworkout snack isn't the "make or break" instance of eating. The meals and snacks prior should provide the bulk of the fuel, and the preworkout snack is to "top off the tank. Ideally, we're not always relying on sugar, but we're giving ourselves enough time to have more whole grain choices. But if sugar is where we're at, due to timing and availability, do it!
I'm not an "athlete", does this still apply?
Yes!
I would argue anyone who moves intentionally or with a health goal in mind is an athlete. You may not be competing, but if you're trying to challenge and improve your body, it needs fuel to work it's best.
Won't I burn more calories (or fat) if I go into a workout fasted?
No
I know, it seems counter intuitive to eat if you are trying to lose weight. Here's the deal, even if you're trying to make your body smaller, training fasted doesn't benefit the effort. If you put in minimal fuel because you're scared of calories, workouts not only feel terrible (making you less likely to return for a 2nd round), it also compromises how hard you can work and the results you see. Additionally, it can increase stress responses within the system that dysregulate appetite and reduce adaptation.
Additionally, going into workouts under-fueled because you are restricting what you eat means that your glucose stores are low. If glucose is low, the body is much likely to pull amino acids from muscle as fuel. If you are losing muscle, you are doing the opposite of training or health...
Application and Timing
If you workout first thing in the morning...
...you likely only have 30-60 minutes before you start moving. Ideally you're relatively fueled from dinner (and not starving). If your workout is less than an hour and not that intense, you might be able to get away without fueling morning of. If you're working out an hour or more OR working really hard, grab something that digests quickly (starch and sugar). Completely fine to add a little fiber / fat / protein, but it should be a small % of the overall fuel to avoid stomach upset.
If you workout in the afternoon...
Ideally you likely had lunch 2-3 hours before. Technically whatever you ate at lunch should be enough to fuel an hour workout. But you may want to add a quick carb source if 1.) You didn't have starch at lunch (eg, you just ate vegetables + meat) 2.) You skipped lunch OR ate lunch >3 hours before your workout or 3.) Your workout is more than 90 minutes
If you workout in the evening...
If you are a late night warrior, it can be tricky to balance food and exercise. Eating a boat load of veggies and meat before a workout is a recipe for misery. Additionally, saving dinner for after the workout may feel tricky. You may consider 1.) Break dinner into 2 instances - eat the starch portion and a little meat before. Eat the remaining starch, meat, and veggies after 2.) Eat an earlier dinner and a refuel snack after
Moral of the story…
There are SO many reasons to eat before training…and virtually zero reasons not to. What you eat and how much you eat depends on the training that you’re doing. My job as a dietitian and personal trainer is to help you line up your performance goals with your fuel selection in a way that leaves you energized.