Ahoy Matey,

This is an interesting idea and I think it has merit, but at the same time it’s important to consider broader variables.

The notion of guiding intensity by relative hunger could work if you were able to anticipate that hunger before it strikes. For example, even if you start a workout at a high intensity you likely won’t feel the need for exogenous calories until at least 45-60min in. For a lower-intensity session this could be true for the first 2-3 hrs. As such, your perceived exertion won’t have the nutritional-demand metric to rely upon for guidance and adjustment.

Additionally, much about how you feel in a workout – high or low intensity – with regards to nutritional needs will come from your diet pre-workout, either from earlier in the day or even the day before. Have you been calorically deficient and under a high training load for several days? If so, even a low intensity workout may have you craving that Snickers bar in your pack within the first 20min (what?! You don’t carry Snickers bars??). Conversely, you may have been eating quite well and resting a lot in prior days, so the effort of what should be considered Z3 actually feels quite mellow through the lens of the caloric input paradigm you described, and you may mistakenly run what is supposed to be an aerobic training run at too high an effort.

I’m not disguising my bias very well; i think perceived exertion, whether via nutritional/hunger measures or simply how the muscles and breathing feel, can be useful data but should be paired with the relative objectivity that a heart rate can offer. If the goal is to be limiting caloric input to only when needed, you can still accomplish that, but at the same time you may save yourself some frustration by better gauging what the actual workload on your body is during a given workout.

Hope that’s helpful!
Sam.

I agree with Sam. While the idea may have some merit in general, there are too many variables for it to be a consistent method to determine intensity. Also, if hunger is the measure, then only after your session do you know if it was the right intensity. That’s backward. You want to know at the start what the correct intensity is.

With respect to the variables, here’s an example of why it’s unreliable. I often do super easy doubles (morning and afternoon sessions) due to schedule constraints. I get up, have a coffee while I do some mobility work, and then go for a run. I never feel hungry or bonky on these morning sessions.

In the afternoon, I do the same: have a coffee (but skip the mobility work), and go for a run. Although it’s at the exact same intensity, if this second session is four hours-ish after lunch with no snacks in between, I usually bonk quite quickly at about 30 to 45′ into it.

From what I’ve read about fasted sessions, morning sessions are easier to tolerate because liver glycogen is depleted, but muscle glycogen is not. Our brains have been sucking on the straw of liver glycogen through the night, but our muscles have been inactive so their glycogen is preserved.

But by the time the afternoon rolls around, both liver and muscle glycogen may be depleted depending on what has (or more accurately, hasn’t) been eaten that day.

I think you can take your lack of hunger as a good sign that your aerobic metabolism is improving. I just wouldn’t use it as an indicator of intensity.

I was wondering if this is one reason why physical jobs are not always the best for training as you probably just float around in the middle or bottom of zones?

No, absolutely not. Physical jobs are not good for training because they aren’t training. They’re too non-specific. Fatigue doesn’t create fitness; it’s just a byproduct. Fitness comes from conditioning your muscle to work at a goal intensity while practicing the mechanics of the event.

Swinging a chainsaw all day will make you a fitter chain saw swinger. But it won’t make you a fitter anything else.

Hey Matey,

Circling back here as I’ve been thinking more about what you wrote and your follow-up. Semple’s comments above are spot-on and I will reiterate that using anything other than HR as a primary measure of intensity while training is fraught with potential mis-reads and risks of overdoing it.

BUT – if I understand your questions correctly now, you are wondering whether you can determine macro-changes in your aerobic capacity based on how your hunger needs ebb and flow at certain intensities in training? I.e. you’re not trying to use hunger as a day-to-day intensity metric, but rather you are interested in using it once in a while to check and say, hey, i didn’t need to eat anything on that 3 hr run yesterday at an easy effort, and i performed the same (or better) as i did two months ago when i did it at the same intensity AND had to eat a lot. Therefore, my aerobic capacity/metabolic efficiency must be better. In this example i think it can indeed be useful, so if this is what you were getting at in your first post, then I agree!

Sam.