Anonymous asked this question on 5/4/2000:

Does the weight gain come from eating more or from a slower metabolism?

Thank you.

desertphile gave this response on 5/4/2000:

It is generally considered to be both. I'll see if I can explain one hypothesis on why people eat more while on anti-depressants.

One of the symptoms of typical depression is a loss of appetite, which some have categorized as "consummatory anhedonia." In atypical depression, one eats and sleeps too much, which can possibly be categorized as "appetitive anhedonia." This is a continuum, and all depressives fall somewhere on that scale--- even in the middle, where eating and sleeping is "normal" (average).

In typical depression one will go out and buy food, but just does not feel like eating it. In atypical depression, one will not feel like going out to buy food, but will eat all that is available around the house. Their "hedonic" (pleasure) inhibitions are different, so it is their MOTIVATION to acquire and eat food is different. The typical depressive will get some pleasure out of "hunting for food" but not much pleasure in eating it; the atypical depressive will take no pleasure in "hunting for food," but will take much pleasure in eating it. The point is, as long as food is available, the atypical depressive will eat it.

Now along comes an anti-depressant that moves the individual closer to the center of the hedonic scale. The goal is to balance the pleasure from "the hunt" with the same pleasure as "the consumption of the hunt." With typical depressives, their "consummatory anhedonia" decreases and the consumption increases. In atypical depression, "appetitive anhedonia" increase and the appetite decreases.

This is why SSRIs change a person's weight.

The most common warning about the side-effects of the SSRI anti-depressants is WEIGHT LOSS, not weight gain. This is why anorexic people should be very closely monitored when taking SSRIs and other anti-depressants: their seeming uninterest in food is not a function of depression, but body image. One should not see the anorexic's seeming lack of interest for food as typical depression, so "consummatory anhedonia" may not apply, and the movement along the hedonic scale may be moved in the "wrong" direction for the anorexic taking anti-depressants. Anorexics have "healthy" appetites: they do not eat for other reasons / causes--- often thought to be social.

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Anonymous rated this answer a 5.

Thank you. I guess I'll have to either stop eating so much or run around a tree for a few hours every day.