Thermogenic effects

Thyroid hormones are intimately involved in regulating the basal metabolic rate. Liver tissue of animals given excess thyroxine shows an increased rate of 02 consumption and increased heat output (thermogenesis), but the ATP concentration in the tissue is normal. Different explanations have been offered for the thermogenic effect of thyroxine. One is that excess thryroxine causes uncoupling of oxidative phosphorylation in mitochondria. How could such an effect account for the observations Another explanation suggests that the thermogenesis is due to an increased rate of ATP utilization by the thyroxine-stimulated tissue. Is this a reasonable explanation Why ... 

Body temperature tends to rise slightly in some users of oral contraceptives (286,287) Progesterone has a mild thermogenic effect, reflected in changes in body temperature during the normal menstrual cycle. Mild pyrexia in users of oral contraceptives may reflect this, but the patient should always be examined to exclude infection. 

Samantha Heller may have said it best when she told The Early Show that food and supplement companies "like to throw around terms like thermogenesis. " In fact, the word is used in ways—mainly in sales pitches—that are not accurate. What follows are a few other substances that claim to have thermogenic effects—or at least, something like them. 

Hansen DL, Toubro S, Stock MJ, Macdonald IA, Astrup A (1998) Thermogenic effects of sibutramine in humans. Am J Clin Nutr 68 1180-1186... 

Tappy, L., Randin, J.-R, Felbcr, J.-P, Chiolern, R., Simonson, D. C, Jcquicr, E, and EieFtonzo, R. A. (1986). Comparison of thermogenic effect of fructose and glucose in normal humans. Am. ]. Physiol 250, E718-E724. 

A 4-year-old girl with accidental salbutamol intoxication (2.3 mg/kg) developed fever (38 C) besides the classical signs of salbutamol intoxication (31). Since she had no identifiable focus of infection the possibility of a thermogenic effect induced by increased adrenergic stimulation due to salbutamol intoxication was considered. 

A potentially harmful effect is the stimulation by E of potassium ion movement from plasma into skeletal muscle and liver P2), which can lead to hypokalemia. This effect is accompanied by a decrease in potassium ion excretion by the kidney. The ability of E to stimulate plasma membrane Na+,K+-ATPase activity in skeletal muscle P2) may partially explain this hypokalemic action, as well as the thermogenic effect of the hormone (see below). 

A study by Dulloo et al. showed that caffeine and catechins produced a thermogenic effect via sympathetic activation of NE, and that the effect of green tea extracts on the metabolic rate in humans is greater than that explained by caffeine content per se. In table 13.2, diurnal, nocturnal, and total 24 h energy expenditure values are presented for placebo, caffeine, and green tea extract. Diurnal energy expenditure... 

Fundamentally, there are only two ways to treat obesity reduce El and increase EE. Thermogenesis and fat oxidation are to a large extent under the control of the sympathetic nervous system and its neurotransmitter norepinephrine after a rational approach for obesity management. In this context, there has been much interest in the potential thermogenic effects of many compounds extracted from plants, namely, caffeine from coffee and tea, ephedrine from ephedra, and capsaicin from pungent spices, largely because of their potential to modulate catecholamine release and activity. ... 

Direct and Indirect Thermogenic Effects of Anorectic Drugs... 

Since that time, few researchers have been concerned with the thermogenic effects of anorectic drugs. Instead, most research on anorectic drugs has focused on elucidating the mechanisms through which these drugs inhibit appetite, in an attempt to find more effective anorectic drugs with diminished side effects and abuse potential. 

Table I. Anorectic Drugs Which Have Been Demonstrated to Have Direct Thermogenic Effects...

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