Energy and Structure: What can RQ tell us?

I wanted to do a short post quickly before I start packing my apartment to move early this week. Here I just want to look at RQ as a measurement and what it can tell us. I will write more about RMR and how it relates to RQ including different physiological states that influence RQ such as birth, what happens to RQ at the start of breast feeding, how thyroid hormones effect RQ, etc. once I get into my new apartment.

There can be a problem when reading papers as to what it exactly means to have a “high metabolism”. The phrase is loosely defined. But some people, including Dr. Peat, define the strength of the metabolism based on the RQ (respiratory quotient). The RQ is essentially the ratio of carbon dioxide eliminated to oxygen consumed.


RQ = C02 eliminated / O2 consumed

A RQ closer to 1 typically means more carbohydrate is being burned and a value closer to 0.7 typically means fat is being burned.

For some reason there is the idea that a high RQ closer to 1 is the same thing as a “high metabolism”. I don’t really know how RQ became associated with the rate of the metabolism. RQ tells you essentially what fuel you are burning, nothing about the rate of your metabolism.

“On a normal diet, his weight was 152 pounds, and his metabolic rate was from 9% to 12% below normal, but after six months on the diet it had increased to 2% below normal. After three months on the sugar and milk diet, his weight leveled off at 138 pounds. After being on the diet, when he ate 2000 calories of sugar and milk within two hours, his respiratory quotient would exceed 1.0, but on his normal diet his maximum respiratory quotient following those foods was less than 1.0.

The effect of diabetes is to keep the respiratory quotient low, since a respiratory quotient of one corresponds to the oxidation of pure carbohydrate, and extreme diabetics oxidize fat in preference to carbohydrate, and may have a quotient just a little above 0.7.” ~Dr. Peat

“His respiratory quotient increased (producing more carbon dioxide), as well as his rate of resting metabolism.” ~Dr. Peat

“Maintaining a high rate of oxidative metabolism, without calorie restriction, retards the accumulation of PUFA, and a high metabolic rate is associated with longevity. An adequate amount of sugar maintains both a high rate of metabolism, and a high respiratory quotient, i.e., high production of carbon dioxide.” ~Dr. Peat

“At high altitude, or when taking a carbonic anhydrase inhibitor, there is more carbon dioxide in the blood, and the serum phosphate is lower; sucrose and fructose increase the respiratory quotient and carbon dioxide production, and this is probably a factor in lowering the serum phosphate.” ~Dr. Peat

Needless to say, the only point with which I agree with from above is that carbohydrate increases RQ and fructose is effective at the task. The literature supports that.

It seems that as we age RQ increases and if you believe that a higher RQ is a measure of the rate of metabolism this can lead to some paradoxical conclusions. If that is what you think, you don’t have to do anything, your RQ will increase without any dietary intervention.

In obesity and diabetes it is observed that RQs tend to be higher (more towards 1). Aging, disease, and other metabolic derangements at the end of the day all basically stem from hypoxia (Douglas & Haddad, 2008).

“Similarly, individuals with a high 24-hour respiratory quotient (RQ) are more likely to gain weight than those with a low RQ.” (Ravussin, 1995)

“Over a 7-year period, mean unadjusted and adjusted 24-hour RQ increased (p < 0.01). Cross-sectional data analysis showed that both the unadjusted (r = 0.19, p < 0.03) and adjusted (r = 0.19, p < 0.03) 24-hour RQ correlated with increasing age while adjusted BMR (r = -0.21, p < 0.02) correlated inversely with age.” (Rising, Tataranni, Snitker, & Ravussin, 1996)

“Subjects with higher 24-h RQ (90th percentile) independent of 24-h energy expenditure were at 2.5 times higher risk of gaining greater than or equal to 5 kg body weight than those with lower 24-h RQ (10th percentile).” (Zurlo et al., 1990)

“In contrast obese patients who succeeded to retain the weight loss achieved initially by the VLCD at 2-yr follow-up (weight losers) or those who did not exhibit weight fluctuations (weight noncyclers) were characterized by a significantly lower RQ.” (Hainer, Kunesova, & Parizkova, 1999)

“High nonsleeping RQ (NSRQ) predicted 2-year change in FM independently of energy balance, circulating insulin, and insulin sensitivity. This observation suggests that low postprandial fat oxidation may uniquely predispose obesity-prone individuals to accrual of adipose tissue.” (Ellis, Hyatt, Hunter, & Gower, 2010)

cho thyroidThe real world is a fascinating place.

Now a high RQ is not always associated with weight gain, this is why RQ really should not be associated with the rate of metabolism. If you are into calorie counting, you can have a high RQ on a high carbohydrate diet without gaining weight. But DNL is going to be very active. You’ll be burning fat just as quickly as you make it. Your triglycerides will probably increase, but they might not if you are taking thyroid. which is going to enhance fatty acid oxidation.

Aside: Thyroid hormone itself stimulates DNL. DNL is reduced in hypothyroidism and treatment with T3 increases DNL.

T3 also decreases the RQ (Barbe et al., 2001).

Of course long term you are going to run into a lot of side effects as DNL will eventually not be able to supply the demand T3 places on fatty acid oxidation. This is speculative, but I think a reasonable partial explanation for why a lot of people on a low-fat-high-carbohydrate-diet taking thyroid probably feel better when they eat more saturated fat.


Barbe, P., Larrouy, D., Boulanger, C., Chevillotte, E., Viguerie, N., Thalamas, C., … Langin, D. (2001). Triiodothyronine-mediated up-regulation of UCP2 and UCP3 mRNA expression in human skeletal muscle without coordinated induction of mitochondrial respiratory chain genes. FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology, 15(1), 13–15. doi:10.1096/fj.00-0502fje

Douglas, R. M., & Haddad, G. G. (2008). Can O2 dysregulation induce premature aging? Physiology (Bethesda, Md.), 23, 333–49. doi:10.1152/physiol.00023.2008

Ellis, A. C., Hyatt, T. C., Hunter, G. R., & Gower, B. a. (2010). Respiratory quotient predicts fat mass gain in premenopausal women. Obesity (Silver Spring, Md.), 18(12), 2255–9. doi:10.1038/oby.2010.96

Hainer, V., Kunesova, M., & Parizkova, J. (1999). Respiratory quotient in obesity: its association with an ability to retain weight loss and with parental obesity. Sbornik …, 101(1), 99–104. Retrieved from

Ravussin, E. (1995). Metabolic differences and the development of obesity. Metabolism: Clinical and Experimental, 44(9 Suppl 3), 12–4. Retrieved from

Rising, R., Tataranni, P. A., Snitker, S., & Ravussin, E. (1996). Decreased ratio of fat to carbohydrate oxidation with increasing age in Pima Indians. Journal of the American College of Nutrition, 15(3), 309–12. Retrieved from

Zurlo, F., Lillioja, S., Esposito-Del Puente, A., Nyomba, B. L., Raz, I., Saad, M. F., … Ravussin, E. (1990). Low ratio of fat to carbohydrate oxidation as predictor of weight gain: study of 24-h RQ. The American Journal of Physiology, 259(5 Pt 1), E650–7. Retrieved from

3 Comments Energy and Structure: What can RQ tell us?

  1. K.

    “respiratory quotient (Rq) displayed an age-related decrease (P < 0.001)"

    "long-lived subjects had oxygen volume, carbon dioxide volume, and Rq significantly higher than aged subjects but lower than adult subjects. "
    Sounds like RQ falls over time to me.

  2. Sébastien

    K., I don’t think anyone can explain the reason for the roller coasting values (adult – old – long-lived) – maybe because fasting RQ may not be a valid measure (but could be for other reasons), among other methods, and probably why the controversy in this subject exists + why the regression plots are so “cloudy” in many of these papers.
    After a quick glance, I liked Ellis et al. paper for their considerations of the differing RQ, family history, insulin sensitivity, etc.

  3. Kyle

    Is it RQ that rises with age, or RER? There is a difference, and metabolically speaking a pretty huge one.

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