Thursday, January 6, 2011

Does strength exercise increase nitrogen balance?

This previous post looks at the amounts of protein needed to maintain a nitrogen balance of zero. It builds on data about individuals doing endurance exercise, which increases the estimates a bit. The post also examines the issue of what happens when more protein than is needed in consumed; including by people doing strength exercise.

What that post does not look into is whether strength exercise, performed at the anaerobic range, increases nitrogen balance. If it did, it may lead to a counterintuitive effect: strength exercise, when practiced at a certain level of intensity, might enable individuals in calorie deficit to retain their muscle, and lose primarily body fat. That is, strength exercise might push the body into burning more body fat and less muscle than it would normally do under calorie deficit conditions.

(Strength exercise combined with a small calorie deficit may be one of the best approaches for body fat loss in women. Photo source:

Under calorie deficit people normally lose both body fat and muscle to meet caloric needs. About 25 percent of lean body mass is lost in sedentary individuals, and 33 percent or more in individuals performing endurance exercise. I suspect that strength exercise has the potential to either bring this percentage down to zero, or to even lead to muscle gain if the calorie deficit is very small. One of the reasons is the data summarized on this post.

Two other reasons are related to what happens with children, and the variation in spontaneous hunger up-regulation in response to various types of exercise. The first reason can be summarized as this: it is very rare for children to be in negative nitrogen balance (Brooks et al., 2005); even when they are under some, not extreme, calorie deficit. It is rare for children to be in negative nitrogen balance even when their daily consumption of protein is below 0.5 g per kg of body weight.

This suggests that, when children are in calorie deficit, they tend to hold on to protein stores (which are critical for growth), and shift their energy consumption to fat more easily than adults. The reason is that developmental growth powerfully stimulates protein synthesis. This leads to a hormonal mix that causes the body to be in anabolic state, even when other forces (e.g., calorie deficit, low protein intake) are pushing it into a catabolic state. In a sense, the tissues of children are always hungry for their building blocks, and they do not let go of them very easily.

The second reason is an interesting variation in the patterns of spontaneous hunger up-regulation in various athletes. The increase in hunger is generally lower for strength than endurance activities. The spontaneous increase for bodybuilders is among the lowest. Since being in a catabolic state tends to have a strong effect on hunger, increasing it significantly, these patterns suggest that strength exercise may actually contribute to placing one in an anabolic state. The duration of this effect is approximately 48 h. Some increase in hunger is expected, because of the increased calorie expenditure during and after strength exercise, but that is counterbalanced somewhat by the start of an anabolic state.

What is going on, and what does this mean for you?

One way to understand what is happening here is to think in terms of compensatory adaptation. Strength exercise, if done properly, tells the body that it needs more muscle protein. Calorie deficit, as long as it is short-term, tells the body that food supply is limited. The body’s short-term response is to keep muscle as much as possible, and use body fat to the largest extent possible to supply the body’s energy needs.

If the right stimuli are supplied in a cyclical manner, no long-term adaptations (e.g., lowered metabolism) will be “perceived” as necessary by the body. Let us consider a 2-day cycle where one does strength exercise on the first day, and rests on the second. A surplus of protein and calories on the first day would lead to both muscle and body fat gain. A deficit on the second day would lead to body fat loss, but not to muscle loss, as long as the deficit is not too extreme. Since only body fat is being lost, more is lost on the second day than on the first.

In this way, one can gain muscle and lose body fat at the same time, which is what seems to have happened with the participants of the Ballor et al. (1996) study. Or, one can keep muscle (not gaining any) and lose more body fat, with a slightly higher calorie deficit. If the calorie deficit is too high, one will enter negative nitrogen balance and lose both muscle and body fat, as often happens with natural bodybuilders in the pre-tournament “cutting” phase.

In a sense, the increase in protein synthesis stimulated by strength exercise is analogous to, although much less strong than, the increase in protein synthesis stimulated by the growth process in children.


Ballor, D.L., Harvey-Berino, J.R., Ades, P.A., Cryan, J., & Calles-Escandon, J. (1996). Contrasting effects of resistance and aerobic training on body composition and metabolism after diet-induced weight loss. Metabolism, 45(2), 179-183.

Brooks, G.A., Fahey, T.D., & Baldwin, K.M. (2005). Exercise physiology: Human bioenergetics and its applications. Boston, MA: McGraw-Hill.


js290 said...


isn't resistance training suppose to stimulate a growth hormone response? I mean, how else would one's muscles grow, right?

Ned Kock said...

Hi js290. Actually growth hormone doesn’t seem to lead to significant gains in type II fiber muscle tissue, at least not by itself. For example, young women have significantly higher circulating GH than men, even after both stop growing, and yet women don’t usually put on a lot much muscle in response to strength exercise. GH helps burn body fat, particularly after a SE session.

Ned Kock said...

Here is a post on GH secretion in response to exercise, for anyone interested:

Unknown said...

Hi Ned,

When you said, "one can gain muscle and lose body fat at the same time ... lose both muscle and body fat", is the muscle that is gained or lost an actual gain or loss of muscle cells? Or is it something else?

Ned Kock said...

Hi Jim. In adults gain in muscle is usually through hypertrophy of existing muscle cells, although hyperplasia can also occur (new muscle cells being created; this is a bit controversial). We gain body fat and lose it on a regular basis. The key is to lose more fat than you gain, without losing muscle.

Ned Kock said...
This comment has been removed by the author.
Ned Kock said...

I must add two caveats to the comment above: (a) I don’t think everybody should try to become “skeleton lean”, as the optimal level of leanness probably varies across individuals (see link to post below); and (b) I think that body fat loss should be VERY gradual, ideally no more than 60 g per 2-day period.

With gradual body fat loss, as indicated above, you will only notice meaningful reductions in body weight on a monthly basis. And that is if you don’t gain any lean body mass. If you gain more LBM than you lose fat, you’ll gain weight and still look much leaner.

Any scale variations on a daily or even weekly basis will be due to variations in water retention levels. See post below.

David Isaak said...

This is all from n=1 territory, but it is indeed possible to gain lean body mass while losing fat if 1) exercise is increased, and 2) protein is kept high enough.

It is a commonplace of diet studies that muscle loss is generally less on low-carb diets, but there is usually some in the absence of exercise.

With exercise, it is possible to gain lean body mass while losing fat--although the lean body gains are usually much slower than the fat loss. Last time I was dunked, I had lost 60.5 lbs--but had gained 9 lbs of muscle, which means a fat loss of nearly 70 pounds.

Gary Taubes has argued on a number of occasions that exercise is relatively useless for weight loss, tending to slow it. He attributes this to increased appetite. I think he is disregarding the possibility that exercise may slow "weight loss" loss even though it speeds fat loss. The two aren't interchangeable.

One last note, however: I think that it is important to emphasize lower body workouts to maintain muscle mass during weight loss. I beleive that one reason most people lose muscle on successful weight loss programs is that the lower body is no longer carrying as much weight around, and therefore getting less exercise. If you want to maintain that portion of your muscle mass, you need to work it hard artificially to replace the work it formerly did an carrying around all your extra poundage.

Ned Kock said...

Hi David. Thanks for sharing; and very good points.

Ned Kock said...

The idea that exercise is worthless because we “simply eat more” is completely wrong, at least as far as strength training is concerned. There are probably few things that compare with strength training as a therapeutic strategy, as long as it is done right; and ideally in combination with other diet and lifestyle changes.

Ned Kock said...

And, David, you are absolutely right re. the need of lower body strength training as one loses weight. A common trait of obese folks is that they have very strong legs.

js290 said...

Gary Taubes also didn't define what exercise was. ;-)

I tend to agree with Mark Sisson when he said diet has an 80% influence on one's health. My guess is Taubes probably agrees with that assessment. So my interpretation is if you get your diet in order, you'll make a much bigger effect than if you're doing the wrong types of exercises that may not make you healthier but may make you hungrier and wreck your diet.

Ned Kock said...

I tend to focus more on the message, or idea, than on the person. I agree with js290 in that Taubes doesn’t refer to a specific type of exercise; in fact, my impression is that what he had in mind was resistance exercise. One way or another, I much rather say that I don’t agree with idea X and explain why, than say that I don’t agree with person P. Idea X can be defended by anybody, and P can always change his or her mind.

David Isaak said...

Actually, as far as I can tell, Taubes is dismissive of exercise in any form for weight loss. (He admits that there are other benefits, but is clear that weight loss isn't one of them.) Here's his most comprehensive statement on the subject:

Toward the end of his article, he brings up insulin, but only in the context of carbohydrates and fat storage. The effects of exercise on insulin sensitivity in muscle tissue aren't mentioned...

Ned Kock said...

Oops, I meant to say that: “… my impression is that what he had in mind was ENDURANCE exercise.” If I am not mistaken, he mentioned somewhere that he practices strength exercise himself.

Zbig said...

Hi Ned,
cool blog :)
Long term low-carber, I finally started my strength training 2 months ago and entries like this, that previous one about protein (as well as many in the past that I will turn my eye to) are of real value to me.

Just out of curiosity: do you lift and what "school of thought" you would recommend,


Ned Kock said...

Hi Zbig, thanks. I do a mix of strength training and sprint-like exercises, focusing primarily on cyclical glycogen depletion/replenishment to promote health. My interest in strength training goes well beyond what I do in practice. I think that understanding it is the key to understanding a number of compensatory adaptation mechanisms.

As for schools of thought, I see a lot of people doing quite well with different approaches. Many people do quite well with an “old school” approach, including multiple balanced meals every day. Examples are Scooby ( and Doug Miller ( If they like it, and it works for them and helps them meet their goals, why not? These folks are massive and yet very lean and healthy-looking.

Personally I am happy with the weight loss (see “My transformation” post), which I have maintained, and looking like a thin person who does some healthy manual labor. It fits my lifestyle well. Many people keep trying to become something that they are not, and cannot become, and that eventually leads to health problems.

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varicose veins said...

Exercise is worthless because we "just eat more" idea is completely wrong, at least as strength training. There are probably few things more powerful training as a treatment strategy.

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