But how exactly can excess body weight affect reproductive function in women?
A possible explanation comes from a study by Natalia Igosheva and colleagues from King’s College London, London, UK, just published in PLoS.
Using an established mouse model of maternal diet-induced obesity and live cell dynamic fluorescence imaging techniques, the researchers demonstrated that maternal obesity prior to conception is associated with altered mitochondria in mouse oocytes (eggs) and zygotes.
Specifically, maternal diet-induced obesity in mice led to an increase in mitochondrial potential, mitochondrial DNA content and biogenesis. Generation of reactive oxygen species (ROS) was raised while glutathione was depleted and the redox state became more oxidised, suggestive of oxidative stress. (for my non-technical readers, it suffices to say that none of this is good for the egg or the zygote).
These altered mitochondrial properties were associated with significant developmental impairment as shown by the increased number of obese mothers who failed to support blastocyst formation compared to lean dams.
These studies show that compromised oocyte and early embryo mitochondrial metabolism, resulting from excessive nutrient exposure prior to and during conception, may underlie poor reproductive outcomes frequently reported in obese women.
While the leap from mice to women may seem a bit of a stretch, there is no doubt that in many overweight and obese women trying to become pregnant, weight loss is clearly one of the most effective strategies.
Now all we need are more effective strategies to help manage excess weight.
Igosheva N, Abramov AY, Poston L, Eckert JJ, Fleming TP, Duchen MR, & McConnell J (2010). Maternal diet-induced obesity alters mitochondrial activity and redox status in mouse oocytes and zygotes. PloS one, 5 (4) PMID: 20404917