Does Ketosis Cause An Internal Rise In Body Temperature?

Low-carb burns fat, but can it lead to extra body heat?

Ooh, ooh, ooh,
I feel my temperature rising
Help me, I'm flaming
I must be a hundred and nine
Burning, burning, burning
And nothing can cool me
I just might turn into smoke
But I feel fine

--Elvis Presley singing "Burning Love"

Somebody's turned up the heat up in here and it's gotta be that low-carb diet I'm on, right? That's what everybody does with livin' la vida low-carb when something new happens to them after starting this way of eating--they blame it on low-carb! I mocked this notion in this blog post about an earache a couple of years ago, but what if there is merit to some rather strange side effects of following a controlled-carbohydrate nutritional approach? Hmmmmmm.

There are several things we KNOW will happen to most people when they begin the low-carb lifestyle: their HDL "good" cholesterol goes up, there is a marked improvement in mental health, for women it helps with reproductive health, blood sugar levels are stabilized, they end up having less acne, triglycerides plummet (a VERY good thing!), and so much more I could spend hours sharing with you about. But there are some things that can vary from person to person as one of my readers shared with me in a recent e-mail.

This 43-year old man starting cutting his carbohydrate intake beginning in January 2008 and has lost over 25 pounds so far. WOO HOO! He has really enjoyed this new low-carb lifestyle change, but was curious about an unexpected side effect that has been plaguing him with no apparent cause. Here's what he wrote:

Hey Jimmy,

After lots of searches, I'm having trouble finding out if anyone experiences a sensation of a rise in body temperature while in ketosis. There are some days I feel like I am literally burning up (but I don't have a fever or anything). Coincidentally, usually the next day after this happens, I am down another pound. It's like the hotter I feel, the faster I lose weight.

Is this a side effect of my body burning stored fat and an increase in my metabolism? I'm having a hard time finding an answer in any literature I've read. Thanks for your time!

What an awesome question! Before I started livin' la vida low-carb weighing in at over 400 pounds, I was ALWAYS hot. HOT HOT HOT with sweaty palms and underarms all the time. I felt like I was on fire all the time. But when I went on the Atkins diet on January 1, 2004, I noticed very quickly a cooling effect happening within the first few months. At first, it was kinda weird when I wouldn't sweat anymore. I REALLY liked that because it was so incessant for most of my life.

But then when I'd shake someone's hand, I could tell my hands were much colder than everyone else. It was as if someone turned the thermostat inside my body down to extreme cold when I started livin' la vida low-carb and it still happens to me to this day especially when I drink a lot of water. And the funny thing is the water doesn't even have to be cold for this to happen. Strange, I know, but that's my experience.

So when I read this e-mail asking about getting HOTTER because of the fat-burning effects of ketosis on a low-carb diet, I didn't know what he was talking about since that wasn't anything close to what I dealt with. I had my suspicions about what may be causing it and shared those with my reader:

GREAT QUESTION! I suspect the ketosis is causing the rise in your body temperature because of the fat-burning that ensues in this state.

But rather than guessing and assuming at what the reason for this is, I decided to throw this question to a handful of my low-carb expert friends to see if they had any insights or practical experiences to share with us about this phenomenon. We'll hear from Jackie Eberstein, Dr. Jonny Bowden, and Dr. Richard Feinman with their responses.

JACKIE EBERSTEIN

Jimmy,

I'm at a loss. I've never heard of nor have I experienced this one. As far as I know, there is no mention in research either that I recall. Sorry I can't be more helpful.

That's okay, Jackie! Although having worked with Dr. Robert C. Atkins for three decades treating all kinds of patients with a low-carb dietary regimen, I'm surprised something like this hasn't come up at least a few times. Interesting. Let's see what Jonny Bowden has to say.

DR. JONNY BOWDEN

Hi Jimmy,

I have never actually heard of that happening, but it absolutely passes the "smell test" to me. In fact, when you stop and think about it, this makes total sense on both an intuitive and a biological level.

I suspect what's happening is that thermogenesis is raised in the body, meaning the furnace temperature is up, fat-burning is accelerated, and that is why your reader is experiencing a temporary rise in body temperature. My guess is you are absolutely right about why this is happening.

It certainly makes sense despite my own personal experience. If you are burning fat, then that could cause an increase in heat which leads to an elevated temperature. Finally, let's talk to a biochemist who really knows his stuff--Dr. Richard Feinman from SUNY Downstate Medical Center in Brooklyn, NY and the co-editor of the Nutrition & Metabolism journal.

DR. RICHARD FEINMAN

There are reports in the literature of this kind of observation by subjects in trials of high-fat diets. Little is known, however, of what controls perception of heat and the relation to food consumption.

The phenomenon of diet-induced thermogenesis or thermic effect of feeding (the old name for this was "specific dynamic action"), however, is well known and it is generally agreed that, at least under experimental conditions, consumption of 20% of protein calories, 5% of carbohydrate calories, and 3% of fat calories is "wasted" in increased heat production.

See, for example this 1984 study:

Karst H, Steiniger J, Noack R, Steglich HD: Diet-induced thermogenesis in man: thermic effects of single proteins, carbohydrates and fats depending on their energy amount. Ann Nutr Metab 1984, 28(4):245-252.

Abstract: The diet-induced thermogenesis of 12 healthy males of normal body weight was measured by means of indirect calorimetry over 6 h after test meals of 1, 2 or 4 MJ protein (white egg, gelatin, casein), carbohydrate (starch, hydrolyzed starch) or fat (sunflower oil, butter). The effect of 1 MJ protein was at least three times as large as that of an isocaloric carbohydrate supply.

In mixed meals there is little agreement because of the small number of studies and the fact that it is so complicated with other factors. For example, drinking cold water will increase heat expenditure. We certainly have the idea, supported by both experimental studies and anecdotal observations, that low-carb diets are less efficient at fat storage and that the missing energy may appear as heat. There is also the idea that the underlying mechanism can be related to ketone bodies but it would be impossible to say whether or not this is the cause in the case described by your reader.

So, the jury is still out on the question of whether ketosis brought on by a low-carb diet leads to an increase in body temperature. Has anyone else experienced this on your low-carb lifestyle? Or were you like me and started freezing when you decided to go low-carb? Share your comments about what you've experienced. Are you hot or are you not? :)