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Is Body Core Temperature A Core Factor In Obesity?



Yesterday, on my flight back from Orlando, I happened to sit besides Lewis Landsberg, Professor of Medicine and dean emeritus of Chicago’s Northwestern University Feinberg School of Medicine and director of the Northwestern Comprehensive Centre on Obesity, who is certainly well known to anyone working in the fields of hypertension, autonomic nervous system and obesity.

In our conversation, he drew my attention to a paper published in Trans Am Clin Climatol Assoc, in which he discusses the potential importance of the body’s core temperature in weight regulation.

As Landsberg points out, maintenance of the body’s core temperature (at around 37 degrees centigrade) accounts for almost 50% of total energy expenditure, far more than physical activity or adaptive thermogenesis (which each account for roughly 10% of total energy expenditure in today’s largely sedentary individuals).

Thus, even small differences in core temperature or in the number of calories required to sustain homeothermy, can account for a substantial differences in caloric output and thus body weight both between and within individuals.

Landsberg emphasizes the potential role that differences in the ability to maintain and defend core body temperature may play in weight gain.

For example, it is well known that even a small rise in core temperature can susbtantially alter metabolic rate – each degree C rise in temperature is associated with a 10-13% increase in oxygen consumption.

Furthermore, both metabolic rate and core temperature varies substantially amongst individuals and populations and, perhaps not unexpectedly, there is a clear inverse relationship between mean annual ambient temperature and resting metabolic rate in different geographic regions – higher in the arctic and lower in the tropics.

As regular readers will recall, small differences in the amount of thermogenic brown adipose tissue (which can be stimulated by cold exposure) can account for 100s of extra calories burnt each day.

Landsberg also points out that a fall in temperature is an important part of the adaptive response to energy deprivation (as in dieting).

Interestingly it appears that some people may also experience an exaggeration of the normal fall in core temperature (and therefore burn fewer calories) during nightie sleep.

Although current data is far from conclusive, it could well be that obese individuals may burn far fewer calories than their non-obese counterparts

“due to lower basal core temperature set point; greater nocturnal temperature fall; lesser temperature rise during exercise; lesser post-prandial temperature rise; and a greater temperature fall during fasting or decreased energy intake as in therapeutic dieting.”

Given that core temperature can be measured with a precision that far exceeds our ability to measure any other parameter of energy homeostasis, it is perhaps surprising that we still lack a good understanding of the relationship between core temperature and body weight.

As Landsberg points out:

“Studies of body temperature in the obese under different circumstances (exercise, sleeping, after meals) are feasible and may reveal important differences between lean and obese. If this proves to be the case, a new therapeutic target, body temperature, may emerge.”

I would add to this that there also may well be differences in preferred ambient temperatures, which in turn could affect metabolic rate.

It is no secret that some people prefer and can clearly better tolerate lower ambient temperatures than others.

My guess is that people who prefer the cold or can better tolerate it, likely have a well stoked ‘internal combustion engine’ that happily burns plenty of extra calories to maintain core temperature, while those who dislike and are more sensitive to the cold will rather depend on an ‘external combustion engine’ (their home furnace), don more clothing, or simply move to warmer climates in order to expend fewer calories to maintain their core temperatures.

A further layer of complexity (pun intended) is added to this issue by the fact that subcutaneous fat also serves as a most efficient insulator. So, it may well be that obese individuals do in fact have to burn far fewer calories to maintain their core temperatures than the skinny folks, who, I assume will probably be the first to die of cold exposure.

With the Edmonton winter fast approaching it’ll be interesting to see just how much longer I can go without bringing back the woollens and burn off those extra calories I may have brought back from Orlando.

AMS
Edmonton, Alberta

Landsberg L, Young JB, Leonard WR, Linsenmeier RA, & Turek FW (2009). Do the obese have lower body temperatures? A new look at a forgotten variable in energy balance. Transactions of the American Clinical and Climatological Association, 120, 287-95 PMID: 19768183

13 Comments

  1. Very interesting, as usual. For one who struggles all the time with extra weight, this expanation certainly provides food for thought.

    Sounds like a research study in the making.

    Thanks.

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  2. Taking this extremely correct analysis one step further, hypothasize that body core temperature equates to hydrative/hypoxic conditions. For example, when you boil water, it will begin rapid evaporation only at boiling point. Human thermogenesis is so complexe however its fundamentals can be no different than that of H2O. Optimal fat burning during exercise likely takes place during human “boiling point” or maximal core temperature. Imagine that an obese person cannot reach this core temperature because of a limited delivery of oxygen and blood, and now we know decreased thermogenetic capacity. Even during exerice, obese people are cheated! I use heart rate analysis during all my sessions and often RPE (rate percieved exertion) which I consider an indication of body core temperature (sweat, color, breathing and recovery rate). I would love to be a part of a study that included basal temperature and the obese.

    I think this area of research should be jumped on!

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  3. Hi Dr. Sharma,

    The fundamental assumption here is that the reason low core temperature might be important is it may reduce basal metabolic rate, thus lowering total energy expenditure. However, obese people consistently have higher BMR and TEE than lean people, when appropriate confounding factors such as age, gender and physical activity are accounted for. This is mostly because they have more lean mass and higher leptin. The problem is that higher calorie intake more than makes up for the extra energy expenditure. That’s why I think the “calories in” side of the equation is the main problem.

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  4. Your article interests me for another reason. I am on the overweight side though not obese, but also muscular (a 60 year old woman who greatly enjoys serious weight lifting) which helps me burn calories. For a half year, ever since a bad bout of viral bronchitis, I have been running a body temperature below the 95th percentile for humans (which is lowest around sleeping times so perhaps lower yet when asleep, and highest about supper times), though nothing lower than 95’F, and only twice during that time for a few hours entering the lowest portion of the 95th percentile which begins about 97.8’F. (Confession here that I now only take my temp days apart and sometimes not for as long as week unless I feel “off”; having found the routine an imposition after a few months.)

    My thyroid is fine; one possibility is that I am slowly recovering from hidden adrenal cortical inflammation from the virus. If this does not self correct that will be the next thing tested. I do not feel cold, and if anything the hot flashes I’ve had for 20 years have actually increased a bit, especially the sleeping ones.

    I do take trace mineral daily; a specialist consulted by my internist said that would be needed at my low temps and it does help me feel perfectly well, and reduces cravings, especially the strong salt craving which began after temp drop. Let me have my minerals and exercise, and I feel great.

    Also, I have actually had fewer infections with the body temperature drop than I used to have; perhaps my temp is unfriendly to many human illnesses. Yes, I know that I need treatment faster than when I could run decent fevers if I do get sick, though.

    I’d been dieting (and still am a bit by watching calories and food intake types in a food diary) before the illness. Total weight loss completely stalled with the temperature reduction so I have gone for changes in percentages of adipose and muscle by maintaining the food diary and aiming when possible for an intake that is below maintenance, though that is getting harder with an appetite increase as we enter Autumn and colder weather.

    Although I have had to reduce exercise during ragweed season due to asthma, this lifestyle approach of adding a LOT of exercise has been working well for me. I increased my weekly active exercise to 6 to 10 hours per week, aiming for the higher number, and changed the proportions (when asthma is not kicking up) to have about two to three times as much time in aerobic exercise as in weight lifting. My total weight has not changed but my clothing sizes have, in a good direction, but slowly.

    Oh. and I have put small tables atop tables to make standing desks, and now spend much of my online time standing and gently swaying rather than sitting to also increase caloric expenditure since I know that I have to make up a bit for the Calories not lost to normal levels for homeostasis.

    OH, if useful: I try for between 1,750 to 2,000 Calories per day (though I definitely do slip up at times), with about 20% protein, and usually no more than 20% fat, and the diet including a lot of whole grain, veggies, and fruits. My aim is to not be much different than the lower number on most days and to try to avoid going over the higher one. To keep myself honest I use a computerized diet tracker and a food scale.

    What amazed me is how little is known about sudden body temp drop that is not due to thyroid illness, but reading your article it sounds like too little in known about low core temperature in general, and I do wonder if any others with low body temperatures who have cravings, especially for salty foods, might be helped by their physicians adding trace minerals to their daily routines, and by increasing exercise and altering exercise types if their health permits. (For me the big motivational trick is doing exercise I enjoy, and avoiding the exercise types that I hate.)

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  5. Only you could, by chance, sit beside someone with this background- you must have enjoyed that flight.
    Since losing most of my weight I have trouble with staying warm. In fact, most of the time I have freezing hands and feet and spend a great deal of time in the pursuit of staying warm. Once I “catch a chill” it takes me forever to feel comfortable again. I have attributed this to my lost of insulating fat.
    Maybe it is to my benefit that I am shivering because I am burning more calories?
    Perhaps my thinking is wrong on this- Does feeling cold even relate to core temperature?

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  6. I can actually answer a bit of Jodi’s question on feeling colder from experience as someone who is doing okay with hypothermia. Part of the answer is that it can depend on WHY a person feels cold, and if the cause is even related to hypothermia.

    I am NOT a physician so use a healthy grain of salt when reading this.

    Should commenting in this way be inappropriate, please, feel no guilt about deleting this post. I am fully happy to be moderated.

    Some other causes can be:
    1. just getting used to weight loss; you will feel chillier with less subcutaneous fat
    (something to which my husband is adjusting after desired weight loss of 50 pounds recently)
    2. circulatory causes (knew someone in that position)
    3. Raynaud’s Syndrome (but then discoloration is expected and you did not mention that; I knew a young woman with that long ago)
    4. anemia (been there)
    and I am sure that there are other causes upon which I have no knowledge

    If you want to know if your core temp may be low then first: take your temperature like you normally would. At first take it several times a day because some of us are warmer at certain times. In degrees Fahrenheit the normal human adult body temp range is 97.8 to 100, with 96.8 being the mean. (I usually run in the 96s for the last half year but have been both above and below that, as low as the low 95s is not unheard of for me.) In degrees Celsius the low boundary of normal range (97.8’F) is 36.55′ C.

    Does running a low body temperature mean that you will feel cold? Not necessarily. Mine traces back to damage from a virus and I do NOT feel cold. On the other hand, if the problem were with my thyroid I would feel cold, and if you are a woman over 50 years of age then know that thyroid problems are not unusual. Your physician can test your thyroid easily with blood tests if that is a possibility.

    Again, I am NOT a physician, just someone with hypothermia who has adjusted to that change in my life with added exercise (especially added aerobic exercise), careful monitoring of diet, jumping faster for medical care if an infection is caught, and taking trace minerals, as well as with adjusted expectations for rate of adipose tissue weight loss.

    Also, I do NOT know if there are any reasons that an oral temperature would not correspond to core temp in others, but am certainly more than willing to learn.

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  7. there are studies from the 1990’s ( even 1980 ‘s) where obese patients were put into tanks of water to measure heat output, these people were burning 4000-5000 calories a day, and there is evidence that obese patient’s mitocondria are not efficient and waste energy, generating heat, which improves when they loose weight

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  8. Yep, I’ve known this for a long time. Low core body temperature is one of the key symptoms of hypothyroid, and the lowered metabolic rate driving this is suspected to be largely responsible for the inability to lose weight.

    I’ve been monitoring my basal body temperature for several years now. When I first started regaining after a long-term weight loss, my basal body temp was hovering around 97 – lower than average, but within reason. In the last few years when my body has stubbornly resisted weight loss despite eating 1000-1500 calories on various plans (low-, mid-, and high-carb) and daily exercise, my body temp has dropped to the low 95s. I’ve been thoroughly tested for thyroid, cortisol, hormone, and blood sugar imbalances and everything comes back normal. My low body temperature is the only reason I can figure for my utter inability to lose weight despite eating very healthily and exercising. My question is – what can I do about it??

    @ Stephen Guyanet re: “However, obese people consistently have higher BMR and TEE than lean people, when appropriate confounding factors such as age, gender and physical activity are accounted for. This is mostly because they have more lean mass and higher leptin. The problem is that higher calorie intake more than makes up for the extra energy expenditure.”

    Data, please? Many of Dr. Sharma’s articles right here cite studies showing that obese people do not eat more or exercise less than non-obese people. My own personal experience, and that of many people I know, also disproves this notion. So what are you basing these presumptions on, other than a biased notion that fat people *must* eat way too much because you’d have to eat way too much to get fat? Guess what, not all of us – heck, maybe not even many of us – do.

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  9. What is known on the pharmacology of low body temperature besides that some of us need more trace minerals?

    My temperature drops with alcohol which is expected since it relaxes the capillaries, but it also seems to drop with caffeine consumption though I have not looked at that too carefully since I don’t often consume caffeine. I can’t figure out why that would be, nor what other pharmacological considerations/cautions might be wise with low body temp. It does impose life style changes, but so far for me they have not been an imposition except for the frustration with glacial changes in weight.

    I can’t even begin to say how good it felt to see Viajera’s post because for the last 6 months I haven’t met anyone else with low body temperature who does not have thyroid problems.

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  10. I came across this discussion, and am curious about the effect of episodes of axcillary temps of 101.6 and 102. throughout a ‘normal day…I am 55, 220lbs, 5’5″, excersize fairly regularly, have a very physical job, had a partial hysterectomy @ 35 yo due to endometriosis….I do perspire a great deal, mostly face and forehead, not nessicarily in the axcillary region, arms and legs as well….I do not ‘flush’ externally, my skin does not become red….. I am recently diagnossed with type 2 diabetes, am in the process of loosing weight, have no cardiac history……

    If your theories are correct, I should be thin enough to be INVISIBLE !!!!!! I have tried to approach this with humor, but over the years, when people hug me or shake my hand they say ” Oh, my you are warm…or EEEWWWWW!!!!!!! I have even steamed up a car window or 2…… I am constantly uncomfortable…wondering if anyone has any ideas/ suggestions…. I am concerned about my overall health….it cannot be benificial to my organs to have a nearly CONSTANT fever’!!! Thank you for listening !!!!!!

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  11. There is a new study which might help others here who are chronically hypothermic without the thyroid involved. In PLoS One there is an article: “Neurocognitive and Somatic Components of Temperature Increases during g-Tummo Meditation: Legend and Reality” by Kozhevnikov, Elliott, Shephard, and Grahamm

    Since the full description of the exercise was not given I combined what was with yogic breathing and got results in body temperature increases per under tongue measurement better than happen from running on an elliptical machine.

    Temps after stopped my four short session of the breathing exercise:

    Immediately 97.9’F
    15 minutes later 98.2 ‘F (That says there is probably still calorie burning from the widespread core trembling it caused rather than peripheral effects from capillary dilation)
    30 minutes after stopping 97.5’F
    45 minutes after stopping 97.7’F (but 0.2’F can be within normal variation range)
    60 minutes after stopping 96.5’F so back into my personal hypothermic normal range

    The exercise causes extremely widespread mild trembling all through the core which I suspect is the source of the temperature increase since mere capillary dilation probably would not have had this decrease profile. It is hard to do since the abdomen and thorax have to be held outward with muscles tensed while doing the deep breathing. To make that easier I imagined myself as a dragon, breathing in energy and then erupting flames along my spine when I exhaled. The hand and elbow position shown in the article are essential for neck and shoulder protection since muscles tense so greatly when doing this.

    This is my first time in the approximately 3 years or so that I have been hypothermic that anything other than imposed increases (hot baths which do nothing to burn calories) got me better than a scant few tenths of a degree improvement.

    Oh, and my husband asked if it caused to sweat heavily because he wondered if my body would actively try to return my normal hypothermic range but it did not, just slightly.

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  12. Clarification: by “held outward” I mean that throughout the breathing exercise the muscles of the abdomen and thorax are tensed and made to balloon outward to get the shape of a vase or pot. In fact, they refer to this technique as “vase breathing”. Those who are interested will want to look up the article. If you go to PubMed then click the abstract open there are two links on your upper right of that page which will take you to the free article both at the PLoS site and at another governmental site.

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  13. Today I tried the vase breathing with a different posture: the kneeling position on a kneeling chair because it seemed in my case that would better protect my lower back. It did and the results were every bit as good for temperature increase taken under my tongue. The big thing appears to be doing it long enough to wind up with widespread trembling in the core. The trembling can even be heard in exhales when doing it. The increase improves for the first 15 minutes and then slowly decreases.

    OBVIOUSLY, get okay of treating physician first. That should go without saying, of course, because people here are neither fools nor under-informed.

    BTW, on PBS there is a new show on the health benefits of exercise that may please others here as much as it did me, and PBS also has it at their Public Broadcasting System website. It is titled “the Truth about Exercise by Michael Mosley” which is a bit of problematic title since info is always being added but it does catch attention and the show was a joy.

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