title: Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis.
abstract: OBJECTIVE
  Few randomized clinical studies have evaluated the impact of diet and physical activity on testosterone levels in obese men with conflicting results. Conversely, studies on bariatric surgery in men generally have shown an increase in testosterone levels. The aim of this study is to perform a systematic review and meta-analysis of available trials on the effect of body weight loss on sex hormones levels.
  
  
  METHODS
  Meta-analysis.
  
  
  METHODS
  An extensive Medline search was performed including the following words: 'testosterone', 'diet', 'weight loss', 'bariatric surgery', and 'males'. The search was restricted to data from January 1, 1969 up to August 31, 2012.
  
  
  RESULTS
  Out of 266 retrieved articles, 24 were included in the study. Of the latter, 22 evaluated the effect of diet or bariatric surgery, whereas two compared diet and bariatric surgery. Overall, both a low-calorie diet and bariatric surgery are associated with a significant (P<0.0001) increase in plasma sex hormone-binding globulin-bound and -unbound testosterone levels (total testosterone (TT)), with bariatric surgery being more effective in comparison with the low-calorie diet (TT increase: 8.73 (6.51-10.95) vs 2.87 (1.68-4.07) for bariatric surgery and the low-calorie diet, respectively; both P<0.0001 vs baseline). Androgen rise is greater in those patients who lose more weight as well as in younger, non-diabetic subjects with a greater degree of obesity. Body weight loss is also associated with a decrease in estradiol and an increase in gonadotropins levels. Multiple regression analysis shows that the degree of body weight loss is the best determinant of TT rise (B=2.50±0.98, P=0.029).
  
  
  CONCLUSIONS
  These data show that weight loss is associated with an increase in both bound and unbound testosterone levels. The normalization of sex hormones induced by body weight loss is a possible mechanism contributing to the beneficial effects of surgery in morbid obesity.
authors.affiliation: Sexual Medicine Andrology Unit, Department of Experimental, Clinical and Biomedical Sciences, University of Florence, Florence, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Corona
authors.forename: Giulia
authors.initials: G
authors.lastname: Rastrelli
authors.forename: Matteo
authors.initials: M
authors.lastname: Monami
authors.forename: Farid
authors.initials: F
authors.lastname: Saad
authors.forename: Michaela
authors.initials: M
authors.lastname: Luconi
authors.forename: Marcello
authors.initials: M
authors.lastname: Lucchese
authors.forename: Enrico
authors.initials: E
authors.lastname: Facchiano
authors.forename: Alessandra
authors.initials: A
authors.lastname: Sforza
authors.forename: Gianni
authors.initials: G
authors.lastname: Forti
authors.forename: Edoardo
authors.initials: E
authors.lastname: Mannucci
authors.forename: Mario
authors.initials: M
authors.lastname: Maggi
mesh_terms: D001835:Body Weight / Q000502:physiology; D006801:Humans; D007006:Hypogonadism / Q000178:diet therapy / Q000209:etiology* / Q000601:surgery; D009765:Obesity / Q000150:complications* / Q000178:diet therapy / Q000601:surgery; D015431:Weight Loss / Q000502:physiology*