Lay some knowledge, Letsrun.
Lay some knowledge, Letsrun.
The same as being "big boned" when you are really just FAT.
All sorts of things. Higher thyroid, HGH, testosterone = "faster metabolism." Genetically lower subcutaneous fat and more surface area per lb/ bodyweight = faster metabolism. Propensity to fidget, etc. = faster metabolism. Better insulin sensitivity = faster metabolism. And so on...
Technically, metabolism's function is to convert calories to energy as efficiently as possible, meaning producing the most work with the least fuel. If your body takes very little energy to do a lot of work, it's efficient. Thus, if you're eating very little but doing a lot, you have an efficient metabolism. If you're eating a lot and doing very little and you're thin, you have a very inefficient metabolism, because your body isn't working efficiently enough (even with high intake/low output) to store calories and put weight on you.
tl;dr --> skinny people actually have inefficient metabolisms, fat people have efficient metabolisms, people who eat a lot and run a lot have unremarkable metabolisms.
In this vain, running actually slows your metabolism. This is done to adjust to the higher energy requirements.
themanontherun wrote:
Technically, metabolism's function is to convert calories to energy as efficiently as possible, meaning producing the most work with the least fuel. If your body takes very little energy to do a lot of work, it's efficient. Thus, if you're eating very little but doing a lot, you have an efficient metabolism. If you're eating a lot and doing very little and you're thin, you have a very inefficient metabolism, because your body isn't working efficiently enough (even with high intake/low output) to store calories and put weight on you.
tl;dr --> skinny people actually have inefficient metabolisms, fat people have efficient metabolisms, people who eat a lot and run a lot have unremarkable metabolisms.
Leakiness of cell and mitochondrial membranes has a lot to do with the most proximate answer. That's what's actually causing energy to be used.
Without getting too technical, in most of your cells, roughly 1/3 of all ATP produced is used to maintain Na+/K+ gradients. The use of ATP produces energy. If one has a leakier cell membrane (caused by leak channels or a higher proportion of unsaturated fatty acids), ions will leak down their concentration gradient requiring more ATP to be used to maintain a gradient, which in turn produces more heat. This is essentially why smaller animals have higher mass specific metabolic rates than larger animals; they have a higher percentage of unsaturated fatty acids in their cell membranes. It's an allometric relationship.
Related to this is brown adipose tissues, which are found mainly in rodents, baby mammals, and hibernaters (not adult humans). BAT produces heat by use of a futile proton pump. In normal mitochondria, protons are pumped across the inner membrane to produce ATP using an enzyme, ATP synthase. In BAT, this enzyme has been modified (called an uncoupling protein) so that it it still pumps protons, but it doesn't generate any high energy ATP. Instead, the energy is lost as heat, which is beneficial if you're trying to stay warm in a winter den.
I guess it probably doesn't make much sense if you don't understand general cell biology and biochemistry, but I don't really know how to explain it concisely without going into the details. Anyway, if you really care, you might google some on mass specific metabolic rate, and uncoupling protein, thyroid hormones, etc.
Well that explains the difference between species, but shouldn't human cell structure be pretty similar from person to person?
Do some research on NEAT - Non-Exercise Activity Thermogenesis
Your diet can affect membrane composition. Cholesterol decreases membrane fluidity and leakiness while unsaturated fatty acids increase fluidity and leakiness. Efficiency of absorption and assimilation varies from person to person. Body composition plays a large roll (adipocytes use very little energy). Muscle fiber type and size also affects metabolism, as do mitochondria densities. Thyroid hormone levels are a major factor. On top of those things, people vary on the abundance of enzymes and activity level of those enzymes, which affects metabolic rate.
Probably the two largest factors are simply body composition and T3/T4 levels (triiodothyronine and thyroxine).
Lazy mothers usually have slow metabolism
high metabolism= skinny
slow metablism= fat