Increased levels of body fat in adolescents whose mothers smoked during pregnancy appear to be driven by structural changes in a part of the brain that is involved in reward processing, according to the results of a study published online on September 3, 2012, in Archives of General Psychiatry
The study, which was conducted in Quebec, Canada, included 378 adolescents aged 13 to 19 years, 180 of whose mothers smoked during pregnancy. These mothers smoked an average of 11.1 cigarettes per day during their pregnancies. The researchers recorded participants’ levels of fat intake over a 24-hour period, total body fat levels, and volumes of parts of the brain involved in reward processing—the amygdala, nucleus accumbens, and orbitofrontal cortex.
The results showed that, compared with adolescents who were not exposed to smoking in the womb, the adolescents who were exposed had 1.7 kg more body fat and 2.7% greater fat intake. In addition, their amygdala volume was reduced by 95 mm3 , but there was no significant difference in the volume of the other 2 brain structures.
The researchers speculate that exposure to nicotine in the womb impedes the growth of the amygdala, which predisposes individuals to greater fat preference in their diets, which in turn leads to increased body fat and tendency toward obesity.