The heat is on!

Last week, one of our site members posted a comment to Ch-Ch-Changes about the benefits of heat and cold in losing weight. I think that 36 months ago I would have completely agreed with his comments; now I am not so sure. With his permission, I turned this dialog into a post, because I think there is widespread confusion on our thermoregulatory system and its effect on metabolic rate.

We seem to have an evolutionary hatred of cold. Those that have followed me in the last couple of months KNOW how adamant I am about this approach constituting a layered approach. In other words, I think that once someone has a good handle on solid nutrition and exercise program (that is another debatable topic), then thermal loading is a way to get a boost in the caloric deficit. but one thing is just an absolute truth:

THERE MUST BE AN OVERALL CALORIC DEFICIT TO LOSE WEIGHT.

Ok, I don’t use all caps frequently, but talk loudly often (bad habit). So we should all agree that beyond diet-goop, pills, glycemic indices, and a 1960s vibrating belt, we have to create a deficit in calories – energy – to lose body fat. Ahhh, there’s the rub. We call it losing weight and really we need to lose energy or body fat. Adding muscle increases weight, but it’s rarely seen as a problem. Conversely, sweating dehydrates and results in weight loss and that is not necessarily a gain.

Close is close enough

You see, we use weight as our primary index of obesity. Tim posted a pretty exhaustive lambast of BMI and this NPR piece is also very good; don’t get sidetracked now – read on. Additionally, tracking body fat accurately is a tedious process and that is why I settled in on being precise, not accurate. Precision is aiming at the center of the target and hitting up and to the left EVERY time. Accuracy is aiming at the center and hitting the center EVERY time.

Precise is good enough, because when you subtract last weeks results from this weeks, you get a very accurate trend. Measuring using a tape and plotting total inches combined body fat measured with a scale/fat caliper can be great ways to monitor these trends. Use our thermogenex log sheet to keep the data consistent.

So what does accuracy, precision, and vibrating belts have to do with hot vs cold thermoregulation?

Measuring the Loss

Maybe nothing, but when we are trying to assess body fat loss, or energy deficits, the scale is not always the best indicator of what is going on inside. Water weight is important and it varies GREATLY, especially in hot environments. It also is significantly impacted by diet changes and, incidentally, cold exposure.

What is interesting is that so many diet and exercise blogs, reports and books list an ominous list of scientific references at the bottom of their article. What most scientists can tell on glance is whether or not they actually read the paper. Why? It’s because most often the total reference to the work in diet-fitness-journalist writing is simply what was contained in the abstract, which is freely published on pubmed and other internet sources.

An abstract is sort of a scientific headline: Now Read This: Lab Rats and Monkeys Lose Weight by Not Eating Tunafish on Thursdays. Well, you get the idea. It catches geek (and skeptical) scientists minds, like me who’s first thought is how do rats and monkeys know what day it is while everyone else is wondering about the tunafish. It’s silly, but you get the idea.

Ok, you are with me, I hope, on caloric deficit = weight loss, need a precise (not accurate) way to track change, and lots of “scientific work” is misrepresented or over stated.

Let’s get back to one of the comments from the post and do a little noodling. Here is the quote from Mike

“2 anecdotal experiences come to mind:

1. The sun is an incredible fat burner. I know my fat loss goes to new levels when I spend 15 minutes in the sun. Look at surfers — look at old time bodybuilders, fitness models, etc…. On a side note: We know that vitamin D affects testosterone plus improves leptin sensitivity. So it could be working because of that.

2. Infra-red saunas — the estimates are 500 calories burned doing NOTHING for 30 minutes. Also amazing for detox (sweating is one of the best ways to get toxins out). And my natural bodybuilding champion friend used infra-reds to accelerate his fat-loss and achieve new levels of leanness (sub 6%).”

Ok, first the reason why I like what Matt posted: 2 anecdotal experiences come to mind. This tells me he’s thought about it and is open to a plausible alternate explanation. He’s seen correlation and doesn’t quite know the full extent of cause and effect.

Watch out, goat boat ahead

Interestingly, I use surfers all the time as an example for thermal loading exposure. I don’t just consider the incident radiation of being in the sun and resulting heating of their body like a lizard – I see the total thermal load. Unless you are surfing in 98.6/37F water, heat is leaving your body at 24x times the rate in water vs air. Every time they hit the water, they are dumping heat. In Half Moon Bay, home of the Mavericks, it’s 60F/15C air and 50F/10C year round. Perfect place to thermal load.

Surfers know squid lids, wash thru, claw hand, and surfer’s ear. They also have an EXTREME amount of thermal load and consequently “don the apron” with some of the fattiest, calorie-dense food known and magically stay rail-thin.

In addition to the thermal load of the water, there is another BIG calorie burner no one is thinking about: evaporative loss. It’s always windy and sun or not, water is evaporating off of your body and a huge rate. Think about the fact that the body’s entire cooling system is based primarily on evaporation of water from the skin (sweat). The problem is that the only calories burned happen when the sweat evaporates – dripping or towel drying don’t count.

I would suggest that some of the “suns” effects are actually the effects of rapid evaporative loss combined with constant water cooling and rewetting. Anyone that has gone swimming in the desert knows that you can get EXTREMELY cold when you get out of the pool, despite an air temperature of 110F/43F. The water flashing off your skin in dry conditions definitely removes heat and cools the skin.

So does sweat = cooling and energy deficits?

Not always. When the water comes from outside the body, it adds extra cooling the body didn’t order and this equates to caloric loss deficits. When it is induced by subjecting the body to a hot environment, causing it to activate its built-in perspiration response to dump a backlog of metabolic heat, it’s just thermal regulation. Unless the backlog of heat was caused by running, jumping, shivering, or some other activity, that evaporation is just a thermoregulatory balance.

Likewise, a quick search of the literature on infrared saunas, brought up the work of Biro et al (1). I won’t dig too deeply into this now, because I have questions into the main author, but what what strikes me is that it starts by saying that these saunas increase appetite in normal patients and then later in a group of ten obese, shuts appetite with no change in Plasma ghrelin and serum leptin concentrations.

It goes on to offer additional evidence of a 260lb/117.9kg patient that lost 38.5lb/17.5kg in 10 weeks on a 1600 cal/day diet. I don’t have height, age or sex of this patient, so we can only take a guess at how much caloric restriction, but if he ate nothing I doubt he’d reach the 3.8lbs/1.7kg a week reported. Something else is happening, we just don’t have enough information to know what.

Could skin stimulation fake the body into thinking it is warm and cause it to sweat and actually cool? Not sure and there is not enough information to even guess. I do know that cooling through evaporative loss has been very accurately measured 20-120Kcal/m^2/hr and so at 15 minute exposures, this is not likely the explanation.

I see LOTs of claims on this all over the internet and I’ve not seen much support. What I know has been researched exhaustively is the energy consumed being cold. We know those numbers and my results, along with others that tried, are not outside the explanation of those studies.

I’ll stick with my guns on Point 1 above (surfers) and on point 2 say that I am dubious, but open to other information. I’d like to understand a possible metabolic pathway for increased energy deficit and evaporation or suppression of hunger (in the paper) is not good enough, because complete starvation barely yields this level and we know the caloric intake.

In the end, there is hopefully a little more light to shine on the effects of cold/cool. We know the metabolic pathways of shivering and non-shivering thermogenesis and these can produce from 15-600% boosts in RMR. I think once people get over the aversion to cold, it’s really no sweat.

(1) Biro et al “Clinical implications of thermal therapy in lifestyle-related diseases” (Exp Biol Med (Maywood). 2003;228(10):1245-1249)