1. Orgasm increases prolactin levels:
"This series of studies clearly demonstrated that plasma prolactin (PRL) concentrations are substantially increased for over 1h following orgasm (masturbation and coitus conditions) in both men and women" - Neurosci Biobehav Rev. 2002 Jan;26(1):31-44.
2. Prolactin-deficient animals show greatly decreased body fat storage with no changes in feeding habits:
"The absence of PRLRs in knockout mice was accompanied by a small (5-12%), but progressive, reduction in body weight after 16 weeks of age. Females were affected to a greater degree than males. The reduction in weight in female PRLR-deficient mice (age 8-9 months) was associated with a 49% reduction in total abdominal fat mass and a 29% reduction in fat mass expressed as a percentage of body weight." - Endocrinology. 2001 Feb;142(2):532-7.Click here to read
3. Inhibiting the action of prolactin results in fat-loss and apparent muscle-gain, even without changed in feeding habits:
"Reductions of prolactin secretion by...treatment for 24 days reduced fat stores (abdominal and epididymal fat depots) in hamsters by 25-49% compared with control animals. However, body weights and food consumption were not affected. These results further substantiate an important role for prolactin in regulation of fat metabolism" - Experientia. 1987 Apr 15;43(4):416-7.
4. Increasing prolactin levels causes an increase in body-fat, especially abdominal fat:
"We have recently show marked disruption of reproductive function and weight gain in female rats treated subchronically with [prolactin-increasing drugs]...induced significant weight gain with...increases in ...intra-abdominal fat." -J Psychopharmacol. 2004 Jun;18(2):149-55.
"Weight gain is a common and severe side effect of... [prolactin-increasing] drugs...The results showed [these drugs] increase body weight and subcutaneous fat deposition." - Psychopharmacology (Berl). 2006 Sep;187(4):447-54.
"increased body weight is associated with prolactinomas [prolactin-secreting tumors] and that weight loss occurs with normalization of prolactin levels [treatment with prolactin-inhibiting drugs]. On the other hand, decreased dopaminergic tone in humans is well correlated with obesity. [prolactin-inhibiting drugs increase dopamine neurotransmission]" - European Journal of Endocrinology, 2002, vol. 147, no1, pp. 77-84
It is satisfactorily demonstrated:
1. Lowering prolactin tends to result in body-fat reductions -- especially abdominal fat
2. Increasing prolactin tends to result in body-fat increases
3. Orgasm increases prolactin
Orgasm initiates a series of biochemical processes whereby increases in body-fat -- especially abdominal fat -- and decreases in muscle may occur. Further research is needed to establish a contributory role of orgasm in the process of lipogensis and abdominal obesity, and whether or not this process occurs in humans.