This article is about a decades-old study that found that adequate hydration and cooler temperatures produce greater ketosis. The topic here is different from dehydration after ketosis happens.
The Courtice-Douglas Effect
The featured study is The modification of post-exercise ketosis (the Courtice-Douglas effect) by environmental temperature and water balance.[1]
The Courtice-Douglas effect is the production of ketones while the skeletal muscles move. The amount of ketones produced in the exercise state is just enough for skeletal muscle consumption and does not accumulate in the blood or the urine in increased amounts.
When exercise ceases, the muscles no longer utilize large amounts of acetoacetic acid, and the ketone bodies can then accumulate if liver production continues rapidly.
The Study
The research was done with ten young men, who all did the exercise in warm and cold environments. Ketosis in this investigation was defined as ketonuria above five μ-mole/min. or serum concentration above 1.4 m-mole/l.
Diet
Forty-eight hours before the experiment, ten young men had a diet of 3,000 calories per day consisting of 15% protein, 45% fat, 40% carbohydrates, and unlimited fluids.
During the day of the experiment, the subjects arrived at the laboratory without food. During the eight-hour study, they did not receive food but, at regular intervals, drank measured amounts of water calculated to maintain a positive water balance.
Exercise
Each subject walked ten miles twice. Five of the participants walked inside a warm room first, and the other five started in the cooler outdoors. After a six-hour rest, they switched environments. (Cross-over study).
One walk (2.5 hours at 6-7 km/hour or four mph) was on a treadmill in a warm room of about 24°C or 75°F. After a six-hour rest of lying down, they walked outdoors on a circular track in a cooler environment of 12°C or 53.6°F.
In both times, they were given enough water to maintain adequate urine. (I keep saying this, and you will know why later.) There is a total of twenty results in this experiment.
Urine Ketone Testing
Urine specimens were collected just before and at the end of the walk, and every 2 hours during rest and tested for ketones.
Results
A. In seven out of ten paired results, ketonuria (ketones in the urine) was higher in the cool than the warm environment.
The graph below shows that more ketosis happens after walking at 8-14ºC (45-57ºF) than at 21-25ºC (69.8-77ºF).
According to the authors, warm temperatures are antiketogenic because of the mobilization of more carbohydrates. The mean amount of carbohydrates mobilized for the walk was 78 g. in the warm and 34 g. in the cool.
This excess mobilization of carbohydrates probably explains the diminished ketonuria and may account for the effects of climate on ketosis.
B. Significant ketosis was associated with positive water balance.
Despite the liberal water intake, only three were in a positive water balance for the whole period of walking and recovery. Evaporative and urinary water losses were greater in the warm than in the cool experiments.
The graph below shows that more urinary ketones are produced when there is a positive fluid balance or adequate fluid intake (red). In contrast, those with a fluid deficit of more than 400 have the lowest levels of ketones (blue).
Passmore and Johnson admit they do not have “profitable speculations” on why greater amounts of ketones are detected in positive fluid balance.
My guess is that adequate hydration allows more ketogenic enzymes to do their job.
These findings are consistent with another study done during that era.[2]
Takeaway
Exercising in cold environments and adequate hydration achieves more ketosis. If you are in a warm area, ensure you drink plenty of fluids. Don’t forget to add a bit of salt.
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Reference:
- PASSMORE R, JOHNSON RE. The modification of post-exercise ketosis (the Courtice-Douglas effect) by environmental temperature and water balance. Q J Exp Physiol Cogn Med Sci. 1958 Oct;43(4):352-61. doi: 10.1113/expphysiol.1958.sp001348. PMID: 13591502.
- SARGENT, F., II, et al. (1958).“The effects of environment and other factors on nutritional ketosis,” Quart. J. Exp. Physiol. 43, 345-351.
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