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KHashmi317

98.6 F (37.0 C) is old school

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It seems that long-standing default body temp for the general (non-CR) population is on the high side. 

https://www.scientificamerican.com/article/normal-body-temperature-is-surprisingly-less-than-98-6/

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Normal body temperature is 98.6 degrees Fahrenheit, right? Not so. There is no baseline for humans, and even if there was, it would be closer to 97.7 °F. Temperature also varies across the day, peaking in late afternoon and bottoming out in early morning. It is slightly higher for women than for men as well. For two decades research has debunked the benchmark, set way back in 1868, yet it persists. One important ramification, says Jonathan S. Hausmann, a rheumatologist at Boston Children's Hospital, who led the latest study, is to redefine fever. Most doctors use 100.4 °F or higher, but if “normal” is lower, then the fever threshold should be, too. It also should vary with the daily pattern and be tailored to each individual, Hausmann says: “A child at 99.0 °F at 4 A.M. may be highly abnormal but at 4 P.M. could be within normal limits.”

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I've read quite a few studies on body temperature in humans and it does appear that 37 degrees C is probably not accurate. 

My body temperature on CR is usually between 35.0 to 35.8 degree C.  If my temperature starts going above 36.5 I feel like I have a fever.  I'm guessing others around here experience the same thing.

 

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Also, the normal temperature population data should be updated to modern measuring devices. I've not been using the classic mercury termometer for years. Many people are using the non-contact infrared thermometer, which is pointed on the forehead or temple. 

Edited by mccoy

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The below summary suggests a rather low range of normal temperture for a hand held infrared termometer.  I'll have to find out in my case, AFAI rememeber, it's usually higher than the cited range, I emphasyzed the relevant part. The article is not very recent though, today's devices might be more state of the art.

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Am J Infect Control. 2005 May;33(4):227-9.

A brief report on the normal range of forehead temperature as determined by noncontact, handheld, infrared thermometer.

Abstract

BACKGROUND:

Noncontact forehead temperature measurement by handheld infrared thermometer was used as a screening tool for fever. However, the accuracy data and normal range of forehead temperature determined by this method were not available.

METHODS:

The temperature readings from 3 handheld infrared thermometers were validated against an electronic thermometer. Normal range of forehead temperature was determined by measuring the forehead temperature in 1000 apparently healthy subjects.

RESULTS:

Significant differences were detected in readings obtained by the 3 different handheld infrared thermometers (analysis of covariance, P < .001) The most accurate one was chosen, and the normal range of forehead temperature in 1000 subjects detected by this method was 31.0 degrees C to 35.6 degrees C.

CONCLUSIONS:

Our study shows that commercially available, handheld infrared thermometers require individual validation. Forehead temperature in excess of 35.6 degrees C is suggestive of fever. Further studies are required to confirm accuracy of this value in detecting fever.

 

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Always from the above article, the statistical distribution of 1000 measurements in adults without any inflammatory conditions. Interestingly enough, the study was carried out after the SARS outbreak in South east Asia. Device was held 5 cm from the center of forehead. Ethnicity was Chinese.

 

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Edited by mccoy

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I thought most people and doctors are now using ear thermometers? I've never seen anyone measure forehead temperature.

I use an ear thermometer.

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2 hours ago, Matt said:

I thought most people and doctors are now using ear thermometers? I've never seen anyone measure forehead temperature.

I use an ear thermometer.

I've had a few minor hospital visits over the past few years and it has been forehead measurement, whereas when I was younger (as it 8+ years ago) it was either in the ear or under the tongue. 

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I've got an IR digital thermometer designed for use on forehead or in the ear, but I've found it works best for me in my arm pits.  My forehead reads cool and ear readings can be inconsistent seemingly affected by alignment of the probe.  My readings tend to cycle daily in a range of 97.3F and 98.3F and drop lower when fasting.  I wondered if weight loss had impacted my metabolism as I didn't get a baseline before starting CR.  I assumed it wasn't serious as thyroid tests have been normal.  Nice to see my temperature numbers are normal too.

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I made a few IR measurements on my forehead, in the center and at 5 cm of distance, as in the Ng et al. article above cited.

The results though were pretty different from the article. So far my frontal temps ranged from 36.4 to 36.7  °C in normal conditions (lack of fever and other symptoms). the devices were evidently different ones and no direct comparison is possible. I checked my values across my wife's and they were not significantly different so I'm probably not a statistical outlier. 

An obvious way to proceed if we want to check our temperature changes when not feeling in shape would be to record the baseline temps and baseline variations across the day when in very good shape. It's easy then to check the deviation from the baseline and decide whether our sickness has significantly influenced our immune system (fever or no fever and how significant).

Inter-individual variability in this way is eliminated, whereas the intra-individual variability (time of day, environmental temperature, natural oscillations) is easily accounted for.

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I've always used a mouth thermo. 

I've never measured anything below 96.8F, even at some of my lowest body weight (108 lbs, back in mid 2006). At my std. 115-120lbs, BT usually hovers around 97.1 to 97.5 F. 

EDIT: I'm 6 ft. tall.

Edited by KHashmi317

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How many calories are you guys eating a day?

My calorie intake currently is usually between 1500-1600 Calories per day. Current BMI is around 19. 

The thing is, for quite a while I was sort of just winging but eating the same thing every day. So I'd buy my shopping, usually the same foods, and they'd last a set number of days. But never measured everything precisely aside from the initial measurements I took. Not too long ago I thought about how I struggled to maintain a BMI above 17 on such a low-calorie intake, so maybe I was eating more than I thought. So I got out the scales, made the same food as I always do, but after measuring for 2 weeks it was pretty consistent, with the odd day actually being lower.

It seems that my body has become more resistant to losing weight or I broke my metabolism 😄 I'm not that active at the moment though, mostly working on my websites while sitting down, so maybe that is a factor. Body fat percentage is between 13-14% according to the new scales we have, but not sure how accurate they're supposed to be.

I did change my weight maybe a couple times, to a small degree (roughly 10-15 lbs) over the period of the last 14 years, so I'm not sure if that had anything to do with it. Or maybe it's just the fact that I've been doing the diet a really long time (but then so have many people here).

Apparently, in rodents, a maintaining a higher body temperature and less fat loss were predictive of increased lifespan compared with a greater degree drop in temperature and fat.

I seem to be holding onto fat pretty well, but my temperature is really low. That being said, I'm not to the point of shivering, I don't think it's ever gone below 34.9 Degrees C on my ear thermometer.

An interesting study here measuring body temperature with different caloric intake levels in AN patients. Looks like they used that pill to track internal 24-hour BT. So it'll be a bit higher than other measurements we're discussing here.

 1 Liao CY, Rikke BA, Johnson TE, Gelfond JA, Diaz V, Nelson JF.
Fat maintenance is a predictor of the murine lifespan response to dietary restriction.
Aging Cell. 2011;10:629–639

 

CRbodytemp.jpg

Edited by Matt

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4 hours ago, Matt said:

How many calories are you guys eating a day?

Last two weeks, 2400 kCal. BMI= 23.2. My temp is lingering around 36.7 °C today. Frontal IR temperature and ear temperature are probably not comparable measurements.

Edited by mccoy

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Oral temperature is what I take.  Like the other methods, it has it's limitations.  E.g., your temperature after a hot drink is artificially high; after a cold drink artificially low.  Right now, I'm towards the end of the worst cold that I've had for a long time:  oral temp is 98.1.

Farhead temperature varies a lot also:  If you test after coming in on a hot summer day, you get a high number; in midwinter, a low number.

Ear temperature varies with where in the ear the probe is placed.

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Out of curiosity, I used the oral temperature probe as an ear thermometer -- I inseted the probe into my ear canal.  Result:  97.4.

🙄

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I've never been able to get really spectacular CR bios like testosterone, body temp, etc. At 1400 cal/day, 6 ft tall, and 115-20 lbs, my CR is (and has been) pretty hard-core -- for almost 19 years now.. 

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Hi Khuram!

Indeed; IMO, you may be the most calorie restricted member of the CR Society.   I remember meeting you and Warren at CR2.  My eyes went wide -- I said to myself, ther is someone who is REALLY on CR!

  😉

  --  Saul

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What happened to your website, Khuram? I remember reading it a long time ago, I think you had information about your diet, supplements and other things?

But wow, yeah, that is very strict! 

@Saul What happened to Warren? It seems like a lot of people from the email lists never joined the forum...

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