Laura Gao for NPR
If anyone asked if I get enough exercise, my answer would be unequivocal: Yes, I make a point of carving out time to sweat, get my heart pumping and move around. I probably would not mention that I prefer to drive the half mile to pick up my coffee instead of taking a 15-minute walk. Or that using the drive thru sounds infinitely more appealing than actually getting out of my car. Or that you’d rarely spot me choosing to trudge up the stairs at the end of the day.
None of these shortcuts on their own feel like that a big deal. After all, I worked out today, right? But added up these are slowly sapping a sometimes overlooked source of metabolic health. It’s a concept that goes by the name non-exercise activity thermogenesis, or NEAT, for short. This is essentially all the calories that a person burns through their daily activity excluding purposeful physical exercise.
Think of the low-effort movements that you string together over the course of your day – things like household chores, strolling through the grocery aisle, climbing the stairs, bobbing your leg up and down at your desk, or cooking dinner. “The fact there’s so many things in part explains why it’s so difficult to study, because how on earth do you measure everything?” says Dr. James Levine, an endocrinologist who pioneered research on NEAT while at the Mayo Clinic and now heads the nonprofit Foundation Ipsen……Continue reading….
By: Will Stone
Source: What NEAT means in fitness, and how to get more of it : Shots – Health News : NPR
Critics:
Thermogenesis is the process of heat production in organisms. It occurs in all warm-blooded animals, and also in a few species of thermogenic plants such as the Eastern skunk cabbage, the Voodoo lily (Sauromatum venosum), and the giant water lilies of the genus Victoria. The lodgepole pine dwarf mistletoe, Arceuthobium americanum, disperses its seeds explosively through thermogenesis.
Depending on whether or not they are initiated through locomotion and intentional movement of the muscles, thermogenic processes can be classified as one of the following:
Exercise-associated thermogenesis (EAT)
Non-exercise activity thermogenesis (NEAT), energy expended for everything that is not sleeping, eating or sports-like exercise.
Diet-induced thermogenesis (DIT)
One method to raise temperature is through shivering. It produces heat because the conversion of the chemical energy of ATP into kinetic energy causes almost all of the energy to show up as heat. Shivering is the process by which the body temperature of hibernating mammals (such as some bats and ground squirrels) is raised as these animals emerge from hibernation.
Non-shivering thermogenesis occurs in brown adipose tissue (brown fat)[3] that is present in almost all eutherians (swine being the only exception currently known). Brown adipose tissue has a unique uncoupling protein (thermogenin, also known as uncoupling protein 1) that allows the uncoupling of protons (H+) moving down their mitochondrial gradient from the synthesis of ATP, thus allowing the energy to be dissipated as heat.
The atomic structure of human uncoupling protein 1 UCP1 has been solved by cryogenic-electron microscopy. The structure has the typical fold of a member of the SLC25 family. UCP1 is locked in a cytoplasmic-open state by guanosine triphosphate in a pH-dependent manner, preventing proton leak.
In this process, substances such as free fatty acids (derived from triacylglycerols) remove purine (ADP, GDP and others) inhibition of thermogenin, which causes an influx of H+ into the matrix of the mitochondrion and bypasses the ATP synthase channel.
This uncouples oxidative phosphorylation, and the energy from the proton motive force is dissipated as heat rather than producing ATP from ADP, which would store chemical energy for the body’s use. Thermogenesis can also be produced by leakage of the sodium-potassium pump and the Ca2+ pump.Thermogenesis is contributed to by futile cycles, such as the simultaneous occurrence of lipogenesis and lipolysis or glycolysis and gluconeogenesis.
In a broader context, futile cycles can be influenced by activity/rest cycles such as the Summermatter cycle. Acetylcholine stimulates muscle to raise metabolic rate. The low demands of thermogenesis mean that free fatty acids draw, for the most part, on lipolysis as the method of energy production. A comprehensive list of human and mouse genes regulating cold-induced thermogenesis (CIT) in living animals (in vivo) or tissue samples (ex vivo) has been assembled and is available in CITGeneDB.
The second form of NST occurs in skeletal muscle. While eutherians use both BAT and skeletal muscle NST for thermogenesis, birds only use the latter form. This process has also been shown to occur in rare instances in fish. In skeletal muscle NST, Calcium ions slip across muscle cells to generate heat. Even though BAT NST was originally thought to be the only process by which animals could maintain endothermy, scientists now suspect that skeletal muscle NST was the original form of the process and that BAT NST developed later.
Though scientists once also believed that only birds maintained their body temperatures using skeletal muscle NST, research in the late 2010s showed that mammals and other eutherians also use this process when they do not have adequate stores of brown adipose tissue in their bodies. Skeletal muscle NST might also be used to maintain body temperature in heterothermic mammals during states of torpor or hibernation.
Given that early eutherians and the reptiles which later evolved into avian lineages were either heterothermic or ectothermic, both forms of NST are thought not to have developed fully until after the K-pg extinction roughly 66 million years ago. However, some estimates place the evolution of these characters earlier, at roughly 100 mya.
It is most likely that the process of evolving the capacity for thermogenesis as it currently exists was a process which began prior to the K-pg extinction and ended well after. The fact that skeletal muscle NST is common among eutherians during periods of torpor and hibernation further supports the theory that this form of thermogenesis is older than BAT NST.
This is because early eutherians would not have had the capacity for non-shivering thermogenesis as it currently exists, so they more frequently used torpor and hibernation as means of thermal regulation, relying on systems which, in theory, predate BAT NST. However, there remains no consensus among evolutionary biologists on the order in which the two processes evolved, nor an exact timeframe for their evolution.
Related contents:
- Thermogenesis-triggered seed dispersal in dwarf mistletoe”.
- “The uncoupling protein 1 gene (UCP1) is disrupted in the pig lineage: a genetic explanation for poor thermoregulation in piglets”.
- “Pig Has No Brown Adipose Tissue”.
- “The SLC25 Mitochondrial Carrier Family: Structure and Mechanism”.
- “The SLC25 Carrier Family: Important Transport Proteins in Mitochondrial Physiology and Pathology”.
- Characterization of ryanodine receptor and Ca2+-ATPase isoforms in the thermogenic heater organ of blue marlin (Makaira nigricans)”.
- The direct effect of leptin on skeletal muscle thermogenesis is mediated by substrate cycling between de novo lipogenesis and lipid oxidation”
- “PGC-1α and exercise in the control of body weight”.
- Fever and the thermal regulation of immunity: the immune system feels the heat”.
- CITGeneDB: a comprehensive database of human and mouse genes enhancing or suppressing cold-induced thermogenesis validated by perturbation experiments in mice”.
- “Muscle Non-shivering Thermogenesis and Its Role in the Evolution of Endothermy”.
- Energy assimilation, parental care and the evolution of endothermy”.
- “The uncoupling protein 1 gene (UCP1) is disrupted in the pig lineage: a genetic explanation for poor thermoregulation in piglets”.
- “Molecular evolution of UCP1 and the evolutionary history of mammalian non-shivering thermogenesis”.
- “Increased Reliance on Muscle-based Thermogenesis upon Acute Minimization of Brown Adipose Tissue Function”.
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