2,3,7,8-Tetrachlorodibenzo-P-Dioxin-Induced Weight Loss: A Proposed Mechanism
TCDD caused a dose-related decrease in body weight, food intake, motor activity and total and resting oxygen consumption in rats. In animals treated with 15 μg/kg, the depression in food intake and oxygen consumption lasted 2 weeks. Thereafter, the rats consummed the appropriate amounts of food and oxygen for their reduced weights. However, in rats treated with 50 μg/kg, food intake was insufficient to maintain weight. The results suggest that TCDD causes weight loss by a decrease in energy intake (as opposed to an increase in energy expenditure). The decrease in intake of energy could be due to mal-absorption of nutrients from the gastrointestinal tract and/or reduced food intake. Of these, reduction in food consumption is considered to be the main factor involved. This is because weight in pair-fed control rats stabilizes at a level only slightly higher than in TCDD- treated animals. To determine if TCDD is altering a regulatory system for body weight (as opposed to a system controlling food intake), rats had their body weights reduced by food restriction prior to TCDD (25 μg/kg). Immediately after TCDD they were given food ad lib and they exhibited hyperphagia and weight gain. Thus, the ability to feed is not directly inhibited by TCDD. We propose that TCDD lowers a regulated level or “set-point” for body weight and that the change in food intake reflects the rat’s effort to reach the new weight level.
KeywordsFood Intake Reduce Food Intake Total Oxygen Consumption TCDD Treatment Rest Oxygen Consumption
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