Male partners of obese and infertile women are often also obese and have poor lifestyle habits, and a prospective, controlled cohort study presented at the 2015 Annual Meeting of the American Endocrine Society (ENDO 2015) found that couples’ ability to conceive would improve if these male partners’ obesity markers and lifestyle behaviors improved. Jean-Patrice Baillargeon and colleagues at the University of Sherbrooke, Canada, assessed the effects of a lifestyle intervention on 65 male partners, with an average age of 33 years, recruited from several couples receiving treatment at a fertility clinic at a Canadian academic center. These male partners were assessed for obesity indicators (weight, body fat percentage, waist circumference) and lifestyle habits at baseline and again at 12 months or at the time of a successful pregnancy. About half of the women, along with their male partners, were randomized to receive different interventions, including counseling sessions with a human kinesiologist and dietitian, and nutritional, psychological, or exercise training group sessions. The researchers used t-tests for comparative analyses and multivariate logistic regression to determine the male partner’s independent predictors of couple conception. These male partners were more obese than the general population of Canadian men aged 18-33 years (47% vs. 23%, P<0.001), with more abdominal obesity (waist circumference ≥102 cm; 53% vs. 21%, P<0.001). Compared with the general population, these male partners were less active (29% vs. 58%, P<0.001), consumed at least 5 fruits and vegetables per day less frequently (12% vs. 35%, P<0.001), and ate breakfast less frequently (43% vs. 81%, P<0.001). Improvements in obesity indicators and lifestyle were seen 12 months after the intervention (n=46), but the changes were not significant. A higher proportion of male partners in successfully conceived couples lost more weight (38.5% vs. 10%, P=0.03) and had greater weight loss (-0.32kg±4.55 vs. 2.68±3.19, P=0.02) and lifestyle changes compared to non-conceived couples. The 3 independent predictors of couple conception by the male partner were weight loss (BMI, P=0.04), increased frequency of breakfast per week (P=0.02), and consumption of at least 5 medium fruits and vegetables per day (P=0.05). The researchers said this is the first prospective study to demonstrate that weight loss and dietary changes in male partners can improve couples' chances of conception. The study's findings support the development of lifestyle intervention programs for obese male partners to improve couple fertility and suggest that intervening with women alone is not sufficiently effective to improve fertility.