from the NY Times
Q. Does a person tend to burn more fat exercising outdoors in colder weather or in hotter weather? I am leaning to the colder weather side, since the body has to work harder to keep the body temperature near normal.
A. “Contrary to conventional wisdom, the combination of exercise and cold exposure does not act synergistically to enhance metabolism of fats,” according to a study published in 1991 in the journal Sports Medicine.
The study, done at the Hyperbaric Environmental Adaptation Program of the Naval Medical Research Institute in Bethesda, Md., found that some of the bodily processes involved in fat metabolism were actually slowed down by the effects of relatively cold temperatures on human tissue.
The researchers suggested that the slowdown in metabolic processes might be linked to the constriction of blood vessels in the peripheral fatty tissues when exercise is done in the cold.
The study found that the volume of air inhaled and exhaled in one minute increases upon initial exposure to the cold but may return to rates comparable to those in warm-air exercise upon prolonged exertion.
The heart rate is often, but not always, lower during cold-weather exercise, the study found, while oxygen uptake may increase, something the researchers suggested could be at least in part the result of shivering. C. CLAIBORNE RAY