I think the idea is that 10 grams of sugar for example may get broken down by person A in such a way as to generate 40 calories whereas person B might only generate 30. No violation of the laws of thermodynamics there.
Sucrose sugar will be more uniformly absorbed, as the enzymes required to break it down into fructose and glucose are nearly universal. Glucose metabolism is fundamental to animal physiology. Fructose metabolism is about the same for all humans.
For something like the lactose in cow's milk, the relative metabolic impact for different humans can vary greatly. Some people can metabolize it directly. In others, gut bacteria must digest it into a usable form first. For those people, the composition of their gut flora will determine how efficiently the food energy from lactose is absorbed by their bodies.
That is how the energy calculated by complete combustion in a bomb calorimeter might differ significantly from the energy added to a biological organism. That calorimeter value is essentially the upper limit for "calories in". Using that value means that you still have an unknown value for digestion and metabolism inefficiency in the "calories out" column.
This is why counting "calories in" and "calories out" does not work as expected. The former can be determined easily with the aforementioned calorimeter. But the latter is a complex function that includes "calories in" as an input parameter. You would literally have to wear measurement devices on your body 24 hours a day in a controlled environment, and use special toilets to ever know exactly what your "calories out" numbers are. You would have to calculate thermal losses, water balance, and gas exchange.
This is simply not practical for anyone. Recommending it is madness. It is far more useful to experimentally determine, on a per-person basis, the actions and activities that result in changes in body composition, do the ones that cause adverse changes less, and the ones that cause desired changes more.
There are very few recommendations that work the same way for everyone. But for people that want to reduce their body fat percentage, some stand out. Consume fewer monosaccharides, disaccharides, and trisaccharides. Do strength exercises regularly. Do cardio exercises regularly.
Following those three recommendations often achieve the desired results without the need to count calories. But other ways are possible, some of which are not universally applicable to all humans. In the absence of sophisticated measurement equipment, it is more practical to simply experiment, using plausible hypotheses, until the desired results are achieved.
Do what works. Avoid what does not work. Your results will vary from other animals with different biochemical responses, including other humans that may be closely related to you genetically.
I was commenting on the claim that 10 grams of sugar may give different amount of calories when broken down by different persons.
I've made some assumptions perhaps to hastily that he meant table sugar and by broken down he meant going in full, through the whole route in which body processes sucrose.
If at some stage some part of sucrose is not broken down then you can't count it towards 10 gram. It seems like cheating but assuming the opposite would be like claiming that you can affect breaking down of sucrose by taking it with healthy amount of laxative or dropping some from your mouth as you are munching it.
Besides you said yourself that sucrose, glucose and fructose are pretty much processed by all humans at about the same rate.
Considering all that, claiming that you can get significantly different amounts of energy from (table) sugar would be claiming that basic biochemistry is different for different people (and it's not).
I'm not entirely sure about what you said, that measuring calories spent is so hard. Energy is mostly turned to heat eventually, which is expelled with air you breathe out and the sweat. You could probably estimate the rate of sweating, rate of breathing out, temperature differences, how much sweat evaporated to calculate a lower bound on how much energy a person spent.
It's nice that you can measure upper bound on calories absorbed and lower bound on calories spent. You just match the two and observe if person is dying of starvation or not. If not, then you have got a diet. Write a book and make few persons happy and very many unhappy and some thinner.
Give 10g sucrose to one person, and they may bounce off the walls for a few minutes (increasing caloric expenditure). Give 10g to someone else, and they may feel an urge to eat more (increasing caloric intake). Try it on a third person, and they may want to take a nap (decreasing caloric expenditure).
The chemicals in foods can act upon the body's biochemistry in as drastic a manner as pharmaceutical drugs, together with side effects. People that just consumed large amounts of ethanol have different eating and activity patterns than those who have not. The drunkenness is obvious, but the Buffalo wing consumption still varies.
Sugar intake influences metabolism, just like drugs such as caffeine, nicotine, ethanol, or epinephrine, though those are active at far lower doses.
Thus, the thermodynamic equation of "energy_in - energy_out = delta energy_stored" is certainly valid at a technical level, but it has no practical utility for weight loss. Both energy in and energy out are black box functions that vary by individual, and include types and quantities of foods eaten and current fat stores as input parameters.
The black boxes are not currently well understood. The genome has already been sequenced, but that only led to epigenetics and proteomics. As research in those areas proceeds, we might see a magic pill for fat people that reprograms their black boxes to be more like athletic people. Until then, their effort to lose weight will be a conscious struggle against the natural inclinations of their own body.
And they will continue to be judged as deficient by people who do not need to consciously oppose the biochemical signals of their own bodies, and are therefore ignorant of what that may entail. This is why weight loss is a touchy subject for some people. If you can't be unambiguously supportive and encouraging to someone trying to get fit, it is usually better to just maintain your distance and pretend to not have an opinion. A person who has lost 100 kg will have a far greater understanding of what is involved than someone who has never even tipped the scales past 100 kg in total. And even that person may not understand all that another 200 kg person has to overcome to lose half their body weight.
So here's what you say: "Good for you! You're already a winner! I know you have the ability to reach your goals!"
You don't suggest that they could do better by buying more accurate or more precise scales. They aren't fat because they were lax in their data collection protocols. The stoichiometry of inhaled oxygen and exhaled carbon dioxide won't help. Taking body temperature and recording urine and sweat volume won't help. Anecdotes about how you lost your weight won't help. If you aren't currently activating genes or folding proteins as part of your regular job or primary hobby, you're better off simply providing the psychological support to just keep trying, without getting into specifics.
It has immense practical utility as the only sure way to loose weight. If you can obey it.
> Both energy in and energy out are black box functions that vary by individual, and include types and quantities of foods eaten and current fat stores as input parameters.
The point is you can estimate upper bound of energy_in and lower bound of energy_out.
> The stoichiometry of inhaled oxygen and exhaled carbon dioxide won't help. Taking body temperature and recording urine and sweat volume won't help.
No one does that. People just read values of calories expenditure for various activities from the tables. Same way as they don't own a calorimeters to control their calories intake just read from the tables.
Since you don't need to match the intake with expenditure exactly, rough values are sufficient to let you know if you are in the ballpark of eating less than you spend.
You don't even need values, just cut your meals size in half without changing their contents or number. Or cut their number in half. If you don't loose weight cut them even more. The only trouble is to pay less attention to how you feel and what you want. Physics won't help you with that.
As for the anecdotes ... I lost some weight when I stared eating at Mc Donalds. Because I ate one big mac and fries per day and just some apples apart from that.
I don't know how to put it more simply than this: when energy intake and energy expenditures are both functions of the same input, you cannot guarantee a positive or negative difference solely by adjusting that input, especially when you do not know exactly how those functions work.
Is ( f(x) - g(x) ) greater than or less than ( f(x/2) - g(x/2) )?
If we are at that, turn off your home thermostat few degrees lower and ignore your body. Don't turn on heating in your car. You'll loose weight even faster. The point is to ignore what your body is telling you. That you are going to die. You won't. It's lying to you. Same goes for excercise.
The point is that energy expenditure is a function of foods eaten. You already accept as given that energy input is a function of foods eaten. You may even accept that energy input is not exactly equivalent to the combustion energy of the food.
So you still haven't answered my question.
Is ( f(x) - g(x) ) less than or greater than ( f(x/2) - g(x/2) )?
You cannot answer it. You do not know how the functions f and g work. Likewise, you cannot say that cutting food intake in half will result in weight loss.
Turning down the thermostat and increasing exercise will actually work, as a couple of those thermodynamic inevitabilities. But they still don't address the psychological barriers of weight loss. People don't want to feel hungry, or cold, or exhausted. If they are required to do so to lose weight, it probably won't happen, as being too fat causes them less acute discomfort than the effort to not be too fat.
It is unwise to compare their perception of their discomfort to your perception of your discomfort, in the same way that it is unwise to compare the pain from that one time you got a compound fracture on your agony bone to the pain of a woman in labor. Even if you were objectively hurting more, you just don't do it. Danger, Will Robinson, Danger!
Give encouragement, not advice. Most of the time, a fat person knows exactly what he must do to not be fat. He just doesn't want to change his lifestyle to something that is guaranteed to be subjectively worse and more difficult for months--or even years--before it even gets back to his current level of comfort. He may be angry and frustrated at himself for not being able to do it; that anger is all too easily projected onto other people or things. You really want to help, but there's really not much you can do, other than stand back and play "Eye of the Tiger" at them.
But there is a lower bound. If you carry some bags up the stairs, drink cold water and excrete warm sweat, inhale cold air and exhale hot there is some value of energy that you had to expend that's calculable by physics only.
Also energy intake is a function of lot's of stuff but it is not higher than the energy you could get from food by burning it (also calculated by physics or rather simple chemistry).
If you choose foods and activities so that there is a match between the upper bound of intake and lower bound of expenditure you will loose weight. That sounds like a sure recipe for weight loss for me.
> But they still don't address the psychological barriers of weight loss. People don't want to feel hungry, or cold, or exhausted. If they are required to do so to lose weight, it probably won't happen, as being too fat causes them less acute discomfort than the effort to not be too fat.
Yeah. You are right. But what makes me wonder is why gut reduction surgery works. If people physically can't eat as much as they are used to, they somehow magically are able to bear all the consequences of extremely low energy intake. They don't stuff themselves with pure sucrose and lard to maintain high calories at reduced volume.
> Give encouragement, not advice. Most of the time, a fat person knows exactly what he must do to not be fat.
Fortunately I don't know any fat people that I could hurt by my simplistic approach to what is for me almost purely intellectual problem.
What always made biggest difference for my weight was routine changes. Public transportation or cycling or walking instead of car for commuting, skipping the lunch, unsubscribing from meals cooked by my mom, not buying cheese. That's what I would advice. Skip some meals, change the way you usually move around.
You actually believe this, huh?