Saturday, April 7, 2012

If your NEAT is low, maybe you should chill

I wrote most of this post a while ago, and then forgot about it. The recent blogosphere storm of comments regarding cold-induced thermogenesis caught me by surprise (), and provided a motivation to get this post out. Contrary to popular perception, I guess, cold-induced thermogenesis is an extensively researched topic. Some reasonably well cited references are linked here.

Let us backtrack a bit. When people say that they want to lose weight, usually what they really want is to lose is body fat. However, they frequently do things that make them lose what they do not want – muscle glycogen, water, and even some muscle protein. Physical activity in general depletes muscle glycogen; even aerobic physical activity.

Walking, for example, depletes muscle glycogen; but slowly, and proportionally to how fast one walks. Weight training and sprints deplete muscle glycogen much faster. Whatever depletes muscle glycogen also lowers the amount of water stored in myocytes (muscle cells), effectively reducing muscle mass. Depleted muscle glycogen needs to be replenished; protein and carbohydrates are the sources. If you deplete muscle glycogen through strength training, this will provide a strong stimulus for glycogen replenishment and thus muscle growth, even beyond the original level – a phenomenon called supercompensation ().

In conjunction with strength training, situations in which one burns mostly fat, and very little glycogen, should be at the top of the list for those wishing to lose weight by losing body fat and nothing else. These are not very common though. One example is nonexercise activity thermogenesis (NEAT), or heat generation from nonexercise activities such as fidgeting (). There is a great deal of variation in NEAT across individuals; for some it is high, for others it is annoyingly low.

Walking slowly is almost as good as NEAT for body fat burning, when done in conjunction with strength training. Up the pace a bit though, and you’ll be burning more muscle glycogen. But if you walk slowly you don’t burn that much body fat per unit of time. If you walk a bit faster you’ll burn more fat, but also more glycogen. C’mon, there is no way to win in this game!

This is why being physically active, in a “non-exercise way”, seems to be so important for health; together with strength training, limiting calorie intake, and all the while having a nutritious diet. These are not very common things in modern urban environments. Long term, there isn’t a lot of margin for error. It is ultimately a game of small numbers in the short term, played over long periods of time.

But there is an alternative if your NEAT is low – just chill. That is, another situation in which one can burn mostly fat, and very little glycogen, is exposure to mildly cold temperatures, but above the level that induces shivering (mild cold: 16 degrees Celsius or so; about 60 degrees Fahrenheit). Shivering in general, and particularly intense shivering, is associated with levels of muscle activity that would induce glycogen depletion () (). If muscle glycogen depletion happens while one is fasting, liver glycogen will be used to replenish muscle glycogen, and also to supply the needs of the brain – which is always hungry for glucose.

As the liver glycogen tank goes down beyond a certain point, and no protein or carbohydrates are eaten, the body will use amino acids from muscle to produce glucose. Muscle glycogen will be locked until it is needed. Interesting eh!? The body sacrifices muscle protein but doesn’t tap into muscle glycogen, which is only used to fuel violent muscle contractions. We are talking about fight-or-flight responses here. From an evolutionary perspective, sacrificing some muscle beats losing a lot of it to a predator any day.

Cold-induced thermogenesis is a very interesting phenomenon. The figure below, where open circles represent lean and closed circles obese folks, shows that it leads to different responses in lean and obese folks, and also that it presents a lot of variation across different individuals (like NEAT). This type of thermogenesis actually seems to be strongly associated with an increase in NEAT (); although it seems to also be associated with futile cycles used by the body to generate heat without any movement, as in thermogenesis during hibernation in certain animals () (). Having more brown fat as an adult, or being able to make brown fat more easily, is associated with more cold-induced thermogenesis; and also with a lower obesity risk.

In fact, cold-induced thermogenesis leads to an increase in energy expenditure that is comparable with that of another major energy sinkhole – overfeeding () (). Unlike overfeeding though, cold-induced thermogenesis does not require calories to go in. And, no, you don’t burn more than you take in with overfeeding.

How can one burn fat via cold-induced thermogenesis? Here are some ideas. Set the home thermostat to a mildly cold temperature in the winter (this will also save you some money). When it is a little cooler than normal, don’t wear heavy clothes. Take mildly cold showers, or end a warm shower with some mildly cold water.

What about more extreme cold exposure? It should be no surprise that one would feel pretty good after a dip in ice-cold water; that is, if the person does not suffer from a glycogen storage disease (e.g., McArdle's disease). At least in theory, that type of cold exposure should induce whole-body muscle glycogen depletion, just like an intense whole-body exercise session, with the resulting hormonal changes ().

Growth hormone should be up after that, perhaps for hours. Done right after weight training, or intense exercise, it may have a boosting effect on the hormonal response. But if you do that in the recovery phase (e.g., several hours after the weight training session), it should impair muscle recovery. It would be a bit like doing another strength training session, when the body is trying to recover from the previous one.


Ed said...

Ned, the reference [6] graph looks to me like lean and obese folks have markedly different responses. Can you explain how the graph supports the notion that cold-induced thermogenesis doesn't discriminate between lean and obese folks?

garymar said...

I've heard that after heavy resistance training, a cold soak does wonders for reducing muscle soreness, especially DOMS. I haven't heard of anybody doing it to increase a hormonal response though.

Ned Kock said...

Hi Ed. You are right. I was looking at a different graph when I wrote that, and the wrong one. I will correct the post. Thanks.

Ned Kock said...

Hi garymar. Yes, that idea seems to be based on the notion that somehow the extreme cold exposure leads to a “flushing” of toxins. Empirical evidence to back up that idea is hard to find though.

Anonymous said...

You use the phrase "mildly cold." What does that mean? Can you give a number, or a range? 60-65 degrees F? Or what? Please advise. What's frustrating about all this thermogenesis talk is that no one actually explains in clear, plain English how it is done. Only these crazy extremes: there's no way I'm sitting in 40-degree F bath water with floating ice for 2 hours a day. It will only make me, as a female fat. Note all the female polar swimmers and Japanese pearl divers are counted at about 30-36% body fat. How on earth does this help me lose weight?

Anonymous said...

Ned, another great post. If one was doing intermittent LC - eating 1,000 calories one day and LC, 3,000 the next w/ starches and a work out, how much activity on the low cal/carb day is too much given glycogen depletion causing muscle protein loss?

I thought the point (one point) was to deliberately deplete glycogen stores intermittently to increase stores through compensatory adaptation? Is this at cross-purposes with muscle gain?

montediaz said...


Right in the middle of the article Ned said that mild cold is 60 degrees...

Also if you are eating a ketogenic diet and exposing yourself to temperatures that do not induce shivering...the only fat you'll add on is BAT.

psychic24 said...

I wonder how a person with Mcardle's disease would handle taking a dip in ice cold water.

Ned Kock said...

Hi Anon. It depends on the person – prior adaptations via CA, amount of glycogen stored in the liver, amount of glucose consumed per hour etc. People should know themselves, ideally through numbers:

Ned Kock said...

Hi psychic24. It seems that exposure to intense cold in general is not healthy for people with glycogen storage diseases, including McArdle's disease. Take a look at the comments on the link below; search for “cold”:

Ned Kock said...

Btw, I edited the post, adding a warning for those with McArdle's disease and related disorders. Thanks psychic24!

Ned Kock said...

Another link (below), this one related to glycogen and adaptation. It shows a graph of concurrent glucose and ketone concentrations, in a child with glycogen synthase deficiency (different from McArdle's disease).

One can see here the power of compensatory adaptation, as this child’s body apparently adapted in such a way as to make better use of ketones as a replacement for glucose.

Still, this child may have had trouble with exposure to very low temperatures, and also with glycogen depleting exercise.

Jeffrey of Troy said...

Hi Ned, interesting blog.

My position on related issues: lifting is for muscle, bf% is about diet, walking is for digestion.

More here:

Gladina said...
This comment has been removed by the author.
David Isaak said...

Hi, Ned--

I've been interested in the topic of cold-water immersion for some time.

Have you seen this rather peculiar piece of research? (Central cooling effects in patients with hypercholesterolaemia):

(As an aside, I'm also fond of a hot springs in Northern California, when one can rotate between a poll at 112-114 F, and another with flwoing water at around 45-50 F. We usually do seven cycles of the two. I'm not sure what the metabolic effects are, but the sensation of physical well-being is amazing.)

Ned Kock said...

Hi David. If you look at the numbers in that TC-cold study, the difference between conditions is small, and primarily due to changes in LDL.

Since LDL cholesterol is in part a measure of systemic inflammation, the results could be explained based on a change in the hormonal mix due to the cold baths, leaning slightly toward an anti-inflammatory profile – e.g., increased circulating GH.

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