{"id":8486,"date":"2013-01-05T16:43:37","date_gmt":"2013-01-06T00:43:37","guid":{"rendered":"http:\/\/www.functionalps.com\/blog\/?p=8486"},"modified":"2013-06-24T15:15:39","modified_gmt":"2013-06-24T22:15:39","slug":"body-temperature-metabolism-and-obesity","status":"publish","type":"post","link":"https:\/\/www.functionalps.com\/blog\/2013\/01\/05\/body-temperature-metabolism-and-obesity\/","title":{"rendered":"Body Temperature, Metabolism, and Obesity"},"content":{"rendered":"

Also see:
\nRay Peat, PhD on Thyroid, Temperature, Pulse, and TSH<\/a>
\nTemperature and Pulse Basics & Monthly Log<\/a>
\nThyroid, Temperature, Pulse<\/a>
\nIs 98.6 Really Normal?<\/a>
\nMetabolism, Brain Size, and Lifespan in Mammals<\/a>
\nPromoters of Efficient v. Inefficient Metabolism<\/a>
\nInflammation from Decrease in Body Temperature<\/a>
\nMelatonin Lowers Body Temperature<\/a>
\nMenopausal Estrogen Therapy Lowers Body Temperature<\/a>
\nThyroid Function, Pulse Rate, & Temperature<\/a>
\n\u201cCuring\u201d a High Metabolic Rate with Unsaturated Fats<\/a>
\nFat Deficient Animals \u2013 Activity of Cytochrome Oxidase<\/a><\/p>\n

Metabolism. 2009 Jun;58(6):871-6. doi: 10.1016\/j.metabol.2009.02.017.
\nIs obesity associated with lower body temperatures? Core temperature: a forgotten variable in energy balance.<\/strong> (full paper)
\n<\/a>Landsberg L, Young JB, Leonard WR, Linsenmeier RA, Turek FW.
\nThe global increase in obesity, along with the associated adverse health consequences, has heightened interest in the fundamental causes of excessive weight gain. Attributing obesity to “gluttony and sloth”, blaming the obese for overeating and limiting physical activity, oversimplifies a complex problem, since substantial differences in metabolic efficiency between lean and obese have been decisively demonstrated. The underlying physiological basis for these differences have remained poorly understood. The energetic requirements of homeothermy, the maintenance of a constant core temperature in the face of widely divergent external temperatures, accounts for a major portion of daily energy expenditure. Changes in body temperature are associated with significant changes in metabolic rate. <\/span>These facts raise the interesting possibility that differences in core temperature may play a role in the pathophysiology of obesity.<\/strong> This review explores the hypothesis that lower body temperatures contribute to the enhanced metabolic efficiency of the obese state.<\/p>\n

Some quotables:<\/strong><\/p>\n

“Resting (or \u201cbasal\u201d) metabolic rate (RMR) accounts for<\/span>
\n approximately 80%of energy output.<\/span> About two thirds of RMR
\nis for maintenance of homeothermy (warm-bloodedness); about
\none third is to maintain cellular integrity, ionic gradients, protein
\nturnover, and the like [6-8] Resting metabolic rate is largely<\/span>
\n regulated by thyroid hormones<\/span>, with a minor contribution from
\nthe sympathetic nervous system.<\/strong> Resting metabolic rate differs
\nby as much as 600 kcal\/d for a 70-kg man [8].
\nPhysical activity (exercise) accounts for about 10% in<\/span>
\n truly sedentary humans<\/span>; in addition to intentional activity,
\nthis category includes nonpurposeful motion such as
\nfidgeting, which may differ among lean and obese
\nindividuals [9], as well as upright posture [10].
\nThe remaining 10% is frequently referred to as thermogenesis,
\nwhich means heat production unrelated to physical
\nactivity.<\/strong>”<\/p>\n

“It should be emphasized that, for nonsedentary individuals,
\nthe activity component may be much greater than 10%
\nof total energy expenditure. Evidence has been developed
\nindicating that the combination of activity plus adaptive
\nthermogenesis accounts for about 44% of total energy
\nexpenditure on average, meaning that RMR would constitute
\nabout 56% of total energy expenditure in normally active
\nhumans [15], as compared with 80% in the truly sedentary.<\/strong><\/span>”<\/p>\n

“A lesser ability to dissipate ingested calories is one
\nexample of a thrifty metabolic trait that has evolved to<\/span>
\n promote survival in the face of fluctuations in food<\/span>
\n availability<\/span><\/strong>. Since the initial formulation of the \u201cthrifty
\ngene\u201d hypothesis by James Neel in 1962 [16], the nature of
\nthrifty traits has been the subject of considerable research
\nand speculation. A recent formulation [17] highlights 2
\ndistinct components: (1) decreased metabolic rate and\/or a
\ndiminished capacity for \u201cthermogenesis\u201d and (2) decreased
\ninsulin sensitivity. These 2 components address the 2 main<\/span>
\n physiologic imperatives of starvation: energy conservation<\/span>
\n and protein preservation. A decrease in metabolic rate would<\/span>
\n lead to more efficient storage of calories as fat, thereby<\/span>
\n prolonging survival during famine; during periods of<\/span>
\n abundance and in the face of dietary excess, this trait<\/span>
\n would predispose to obesity. Resistance to the action of<\/span>
\n insulin would divert glucose from skeletal muscle, which can<\/span>
\n use fat-derived substrates, to the brain, an organ almost<\/span>
\n entirely obligated to the use of glucose. In the presence of<\/span>
\n famine, insulin resistance would spare muscle breakdown by<\/span>
\n lessening the need for gluconeogenesis from protein; in the<\/span>
\n face of an abundant food supply, however, and in association<\/span>
\n with dietary excess, insulin resistance would predispose to<\/span>
\n type 2 diabetes mellitus.<\/span><\/strong>”<\/p>\n

“Both metabolic efficiency and insulin resistance, moreover,
\nare known to vary among different individuals in the
\nsame population. The survival value of these thrifty traits,
\nembedded in our genome by natural selection, underlies the
\ncurrent epidemic of obesity and type 2 diabetes mellitus.<\/strong> The
\nravages of obesity in once lean indigenous peoples, such as
\nthe Pima Indians of the US southwest [18,19], the Aboriginal
\npeoples of Australia [20,21], and the Maoris of New Zealand
\n[22], exemplify the maladaptive side of these thrifty traits in
\nthe presence of an abundant high-energy food supply.”<\/p>\n

“The prime importance of energy conservation is demonstrated
\nby the decline in metabolic rate that occurs during
\nstarvation<\/strong><\/span>, a response that involves suppression of sympathetic
\nnervous system (SNS) activity [23]. Body temperature
\nalso falls [24]. This conservative response that limits weight
\nloss during starvation also diminishes the efficacy of low energy
\ndiets in the treatment of obesity [12,14].<\/strong>”<\/p>\n

“Approximately two thirds of RMR is expended in
\nmeeting the requirement of homeothermy [6,7], the maintenance
\nof a constant body temperature of about 37\u00b0C
\n(98.6\u00b0F). In truly sedentary humans where RMR is 80% of
\ntotal energy expenditure, this means that more than 50% of
\ntotal energy expenditure is dedicated to maintaining this
\nconstant core temperature. In normally active humans where
\nthe RMR accounts for 56% of total energy expenditure [15],
\napproximately 37% of total energy output is expended in the
\nmaintenance of homeothermy. This impressive contribution
\nthat warm-bloodedness makes to overall energy production
\nis exemplified by the difference in energy output between
\npoikilotherms and homeotherms; a mouse has a many fold
\ngreater metabolic rate than a lizard of the same weight [37].
\nThis metabolic energy required for homeothermy is thyroid<\/span>
\n dependent and apparently generated principally in mitochondria<\/span>
\n throughout the body of warm-blooded animals.<\/span><\/strong> The
\nadaptive forms of thermogenesis, in contrast, are regulated
\nby the sympathetic nervous system and generated, at least in
\npart, in brown adipose tissue (BAT) [38]. It is of interest that
\nrecent observations using positron emission tomographic
\nscanning have resuscitated interest in functional BAT in adult
\nhumans [39,40].<\/p>\n

The important relationship of body temperature to
\nmetabolic rate is also demonstrated by the effect of
\ntemperature elevation on the rate of oxygen consumption.
\nRaising core temperature by 1\u00b0C is associated with a 10% to
\n13% increase in metabolic rate [41]. During starvation, a fall
\nin body temperature occurs, contributing to the decrease in
\nmetabolic rate noted in this state [24].<\/strong><\/span> Are differences in
\nbody temperature responsible for interindividual variations
\nin RMR? Is it possible that the obese have a lower body
\ntemperature than normal-weight persons? Or that, during
\nperiods of low energy intake or during sleep, the obese have
\nan exaggerated fall in temperature?<\/strong> Good data appear to be
\nlacking; a recent book on energy metabolism and obesity
\n[42], for example, fails to even mention a potential role for
\ncore temperature. Body temperature in the obese is clearly
\nworthy of study given the overriding importance of core
\ntemperature as the major factor in energy expenditure.<\/strong><\/span>”<\/p>\n

“Parenthetically, measurements
\nof core temperature can be made precisely and
\nare free of the conundrum imposed by differences in body
\nsize because core temperature is regulated centrally for the
\nwhole body.”<\/p>\n

“10. Is core temperature lower in the obese?<\/p>\n

Lowering body temperature is an established strategy
\nused by homeotherms to conserve energy. Some animal
\nmodels of obesity, including the obese (ob\/ob) mouse
\n[52,53] and the Zucker fatty (fa\/fa) rat [54], are
\nhypothermic compared with lean controls. Hibernation<\/span>
\n and the lesser state of shallow torpor wherein the<\/span>
\n temperature falls at night are energy-saving adaptations<\/span>
\n used by a variety of mammals<\/span> [55,56] and even some
\nhuman populations such as the Australian Aboriginals
\n[57]. A decrease in body temperature, in fact, occurs at<\/span>
\n night in relation to the sleep cycle in human populations<\/span>
\n [58,59]. A fall in body temperature occurs during<\/span>
\n starvation, as noted above, and in hypoglycemia, an<\/span>
\n acute state of energy deprivation [60-62].<\/span> Recent evidence
\nimplicating fibroblast growth factor 21 in the metabolic
\nresponse to fasting supports the important adaptive role
\nthat temperature plays in the adaptation to starvation.<\/strong> In
\naddition to stimulating lipolysis, fibroblast growth factor
\n21 lowers temperature and induces torpor [63]. Lower
\ntemperature has also been linked to obesity in mice with
\nBAT ablation [64].”<\/p>\n

“11. Quantitative significance of changes in
\ncore temperature<\/p>\n

Some quantitative considerations, although crude, also
\nserve to demonstrate the potential importance of core
\ntemperature. A positive balance of 3500 to 4000 kcal
\nresults, theoretically, in the deposition of 1 lb of fat.
\nWalking 1 mile, a normal-sized individual burns about 100
\nkcal, the amount of energy contained in 10 potato chips
\nand equivalent to 5% of a total energy intake of 2000 kcal\/
\nd. A 1\u00b0C increase in core temperature, by comparison,
\nwould increase metabolic rate by 10% to 13% [41]. In the
\nexample of extreme sedentary existence cited above where
\nmetabolic rate approximates 50% of overall energy output
\n(or about 1000 kcal for a normal-sized person), a 1\u00b0C
\nincrease in core temperature increases expenditure of 100
\nto 130 kcal\/d. Such an individual could achieve energy
\nbalance eating 100 to 130 kcal more per day than one with
\na 1.0\u00b0C lower body temperature. Individuals with the 1\u00b0C<\/span>
\n lower core temperature, thus, would have a thermogenic<\/span>
\n handicap of about 100 to 130 kcal\/d or about 3000 to 4000<\/span>
\n kcal\/mo. In 1 month, this would account for 1 lb of fat, 12<\/span>
\n lb in 1 year, and about 120 lb in a decade, all else being<\/span>
\n equal.<\/span> In the normally active example described above
\nwhere RMR constitutes 37% of total energy expenditure,
\nthe impact is less but still impressive. Under these<\/span>
\n circumstances, the thermogenic handicap of a 1\u00b0C lower<\/span>
\n core temperature might approximate 74 to 96 kcal\/d or<\/span>
\n about 2200 to 2900 kcal\/mo. Greater falls in temperature,<\/span>
\n perhaps during sleep or in response to low-energy diets,<\/span>
\n would have correspondingly greater effects.<\/span>
\n<\/strong>
\n12. Summary<\/p>\n

Given the importance of RMR in overall energy output
\nand the importance of homeothermy as the major component
\nof RMR, core temperature should be evaluated as a potential
\ncause of individual differences in metabolic efficiency in
\nhumans. Assessing core temperature in the obese can be<\/span>
\n done, furthermore, without the confounding need to normalize<\/span>
\n energy expenditure per unit of body mass. <\/span>In these
\nstudies, assessment of core temperature should be done for
\nprolonged periods, should sample day and night temperatures,
\nand should assess the impact of fasting and low energy
\nintake on obese and lean individuals.<\/strong> Cross-sectional, and
\nespecially longitudinal, population-based studies could
\ndefine the role of core temperature in the pathogenesis of
\nobesity. Information gained in such studies, along with
\nresearch into the central nervous system regulation of
\ntemperature set point and the regulation of mitochondrial
\nmetabolism, might enable the development of new therapeutic
\nstrategies designed to enhance energy output<\/strong>.<\/span>“<\/p>\n","protected":false},"excerpt":{"rendered":"

Also see: Ray Peat, PhD on Thyroid, Temperature, Pulse, and TSH Temperature and Pulse Basics & Monthly Log Thyroid, Temperature, Pulse Is 98.6 Really Normal? Metabolism, Brain Size, and Lifespan in Mammals Promoters of Efficient v. Inefficient Metabolism Inflammation from Decrease in Body Temperature Melatonin Lowers Body Temperature Menopausal Estrogen Therapy Lowers Body Temperature Thyroid […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[615,1197,1757,166,92,1756,4,142,69,141],"class_list":["post-8486","post","type-post","status-publish","format-standard","hentry","category-general","tag-basal-temperature","tag-body-temperature","tag-hibernatin","tag-metabolism","tag-obesity","tag-starvation","tag-stress","tag-thyroid","tag-weight-gain","tag-weight-loss"],"_links":{"self":[{"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/posts\/8486","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/comments?post=8486"}],"version-history":[{"count":13,"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/posts\/8486\/revisions"}],"predecessor-version":[{"id":9415,"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/posts\/8486\/revisions\/9415"}],"wp:attachment":[{"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/media?parent=8486"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/categories?post=8486"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.functionalps.com\/blog\/wp-json\/wp\/v2\/tags?post=8486"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}