Except your food expenditures are a sunk cost, and you can't replace them with fuel expenditures.
This is literally comparing apples and gasoline.
This is literally comparing apples and gasoline.
Your body's signals for how hungry you are will not exactly, but still fairly closely, match the calories you burn picking up your new biking habit.
> But the argument could be made that the average American runs a calorie surplus
It really can't; running a calorie surplus would result in constant weight gain. What you actually see is extreme weight stability.
Your response, as far as I can see, says that because Americans already run a caloric surplus, x extra work should only lead to x' - k extra food intake, where the missing k energy is made up by the existing caloric surplus. I responded then and respond again now that this perspective makes no sense; the extra work is an ongoing expenditure and must be exactly balanced by an ongoing intake. For the supposed caloric surplus to be offset against the extra work of extra walking, the person would need to be experiencing constant weight gain beforehand. Nobody[1] is.
You may think that Americans weigh too much, but that's irrelevant; a change in weight is a nearly-pure one-time effect with no influence on dietary requirements. They are eating exactly the amount they already use for the activities they already do.
Am I missing something about your point?
[1] Actually, people with Prader-Willi syndrome will eat if it is possible to eat, no matter how full they are. They will experience constant weight gain if not subject to external control. But they have a serious genetic defect.
It turns out that about 70-80℅ of what most people consume goes into simply keeping them alive (research basal metabolic rate & daily calorific requirement) and the impact of "work you do" is only a small variation - with the above exceptions.
Also interestingly (unable to search the paper reference on phone) there is research that shows that dramatically different lifestyles like Namib desert nomadic hunter-gatherer vs. typical urban don't actually differ on metabolic rates (accounting for non-fat weight)
Why did you think this? Can you articulate a change that metabolism would make to the calculation?
The energy that you need to spend on overhead doesn't go down because you start running.
1: Eat more. This has a linear relationship to the amount of additional running.
2: Do less. By doing less, you can redirect calories that would have been burned anyway to the task of running. You cannot, by definition, redirect calories that are budgeted for the basal metabolic rate.
By paying for the extra running "in kind", by not doing activities you would otherwise have done, it is easy to show a nonlinear relationship between "total running done" and "total calories expended". But that's spurious, it has nothing to do with the energy cost of running. There is a linear relationship between "total running done" and "total calories expended on running", and that is what matters when calculating the cost of running.
The correlation is not that simple as you make it sound.
Edit: To anticipate your next answer: If you run more on top of that, yes, you have to add additional calories somehow and the process starts again. The point is that a car does not have this mechanism at all so it does not make that much sense to compare them like equals.
Why would there be more adaptation to something that occurs rarely than to something that occurs often?
You appear to be describing the following sort of situation:
BEFORE: 100 units of energy expended / day, of which 70 are the rest requirement and 30 go to discretionary activity. This means that 100 units of energy are consumed per day.
THE CHANGE: discretionary activity increases 20%, leading to 106 units of energy expended / day and food intake of 106 units of metabolizable energy / day.
AFTER: discretionary activity stays constant, but "metabolic adaptation" kicks in, reducing energy expenditure back to 100 units / day. Or, "metabolic adaptation" kicks in, causing a diet that had provided 100 units of energy per day before to provide 106 units / day after.
This doesn't happen, and metabolism is not capable of "adapting" in either of those ways. It is capable of adapting by burning more or less mass per unit time, but you can't burn what isn't there. A person's physical structure may change, which changes the efficiency of various activities (though see below!), and their basal metabolic rate, but that is not a metabolic phenomenon. An elevated level of energy expenditure means an elevated level of food intake.
I have found the paper I assume you're talking about, http://journals.plos.org/plosone/article?id=10.1371/journal.... "Hunter-Gatherer Energetics and Human Obesity". First I'll note that it does not investigate, or discuss, caloric intake at all. Fortunately, we know that for a person who is not gaining or losing weight, caloric intake is equal to energy expenditure. It documents that the Hadza, a group of hunter-gatherers in Tanzania, have the same daily total energy expenditure as other populations elsewhere in the world, except farmers (who have higher energy expenditure). It specifically documents that the energy cost of walking is the same for the Hadza as it is for everyone else:
> comparisons of activities common across cultures do not indicate that Hadza muscle and locomotor physiology [are] inherently more efficient. The energy cost of walking (kCal kg^{−1} m^{−1}) for Hadza adults was well within the range of values reported for Western subjects: of 20 U.S and European populations included in a recent meta-analysis of treadmill walking cost, 14 had mean [minimum cost of travel] values below the Hadza mean. [Resting metabolic rate] for Hadza adults measured while sitting averaged 11% above predicted BMR, within the range of values (7–35%) reported for other populations.
It documents that the Hadza have much higher physical activity levels than Westerners. Since physical activity is just as energetically costly to them as it is to us, this requires that their basal metabolic rate be much lower than ours, and it is -- because they are much smaller than we are:
> Regressing [total energy expenditure] on estimated [basal metabolic rate] suggests that group differences in [physical activity level] were related to differences in body size, as the Hadza are significantly smaller than their Western counterparts. In a multivariate analysis controlling for age and sex, the relationship between TEE and estimated BMR did not differ between Hadza and Western subjects. However, because TEE is correlated with estimated BMR with a slope <1.0, PAL (the ratio of TEE/BMR) tends to be greater among smaller individuals; this is particularly evident among men in our sample.
It documents that traveling, being pregnant, and lactating are all uncorrelated with daily energy expenditures, despite being very energetically expensive. Given this, it speculates:
> We hypothesize that [total energy expenditure] may be a relatively stable, constrained physiological trait for the human species, more a product of our common genetic inheritance than our diverse lifestyles.
This means that when Hadza have to do extra work, they overwhelmingly pay for it by doing less elsewhere rather than eating more. That means that the cost of traveling is actually much higher than it would appear just by looking at the energy requirements -- eating extra food is easy, but empirically you are much more likely to pay for traveling by failing to accomplish things that you otherwise would have done. I don't find that reassuring.
IN SUMMARY:
- Hunter-gatherers meet the high energy requirements of their lifestyle by being physically small, which lowers their basal metabolic rate. This strategy is not open to someone deciding whether to walk or drive; they are already the size they are.
- Hunter-gatherers are no more efficient at walking than anyone else, regardless of your several previous comments. No amount of habituation will lower the energy cost of walking (or running, etc.).
- Empirically, energy you spend on running is likely to be made up by failing to do something else that you would otherwise have done. This cost, where it applies, is probably significantly higher than the energy cost. (On the other hand, this result is from a group of hunter-gatherers who aren't necessarily able to eat additional food even if they'd like to.)
Unless one ALREADY does this every day (because then the metabolism already would have adapted) …
It does not mean that if walking three miles takes one apple worth of energy, Example Man actually only needs to consume 0.2 apples in order to walk an extra three miles. He needs to eat the full one apple. This article doesn't consider food as a percentage of your diet at all; it considers food as the cost of moving. Your point isn't relevant.
I started because I wanted to lose like 8-10lbs during a time when I couldn't exercise regularly at the gym which were lost within about 6 weeks.
I walk fast at about 6KM(my gait isn't very long because I wear either jeans or dress pants and I am of average height, but still I'm doing 130-135 steps per minute) an hour according to Google Fit/Apple Health, and I walk between 11-15KM a day (~2-2.5 hours I take a longer route through Hyde Park if the weather is nice and I'm not in a rush getting to or from work).
This daily walk alone increased my daily rough caloric requirement to about 2800-3000 calories, that's 600-800 (k)calories over my daily default if i don't do any physical activity other than getting up and commuting to work on the tube. If i don't increase my caloric intake i would lose between 0.5 and 1 KG a week so in this case and in every other case the "food expenditure" isn't a sunk cost, now you might say that my caloric intake doesn't have much impact on the grand scheme and you would be correct, if I need to eat another slice of pizza or another muffin it doesn't affect anything in the long run, if anything it probably means we might "waste" a bit less food. But given the current cost of each food calorie that you intake if everyone all of a sudden goes up to 3000 Kcal daily requirement it will have an effect on the environment and the economy.
What you should take from it is not that walking is bad for the environment but is that the global food production is highly inefficient ATM, food is cheap especially in the US but it comes at a pretty big price also.