Prefrontal Cortex Response during Preferred Food Consumption as Measured by fNIRS, Level of Intuitive Eating and Current Weight in Post-partum Women
Authors:   , Lanza Lisa , Nasser Jennifer A 
Published: October 2021

Problem: As obesity rates are increasing, more women are entering pregnancy being overweight or having obesity. This places them at higher risk of retaining more weight after each delivery, and consequently, greater risk of chronic illnesses. It is recommended for women to lose 1 to 2 pounds per month between 6 weeks to 12 months post-partum, however, at least 20% of women are 11 pounds heavier after one year post-partum. Food consumption is one of the major causes of obesity, and it is affected by both the hedonic (absence of caloric deficit) control of food consumption in the brain and the physiological signals that are present when there is caloric deficit. Previous studies have shown that activation of the medial prefrontal cortex (mPFC), a component of the brain reward circuitry, is positively correlated with food eaten (grams). Additionally, research indicates that higher intuitive eating levels, eating based on physiological cues rather than emotional or external cues, are associated with lower BMI and greater weight loss in post-partum women (PPW). The primary aim for this study was to assess and compare mPFC activity during food intake and the amount of food consumed in PPW and nulligravida women (NGW). Additionally, this study aimed to assess the association between intuitive eating levels with mPFC, amount of food consumed and BMI in PPW and NGW as well as weight change between end of pregnancy and current weight in PPW only. This study had two Experiments. In Experiment 1, the association between mPFC, amount of food consumed and intuitive eating was assessed in PPW and NGW. In Experiment 2, the association between intuitive eating, BMI was assessed in PPW and NGW and weight change after pregnancy was assessed in PPW. Methods: For both experiments, women completed a phone screening to determine eligibility. For Experiment 1, thirty women (10 PPW, 20 NGW) were included. Participants visited the lab and were asked to consume an ad libitum amount of a previously designated preferred food. The mPFC activity was measured during food consumption using functional near-infrared spectroscopy (fNIRS). Food was weighed before and after the eating episode. The Intuitive Eating Scale (IES) total score (score across subscales) was used to assess intuitive eating. For Experiment 2, one-hundred and thirty women (62 PPW, 68 NGW) were included. This experiment was completely online and it included the Hunger Visual Analogue Scale, weight trajectory questions and the IES. Results: For Experiment 1, correlation of mPFC activity versus food intake were not significant in either group (rs (8) = 0.418, p = 0.115, rs (18) = -0.28, p = 0.116), PPW versus NGW, respectively). The Fisher r-to-z transformation for comparing the relationship between mPFC activity and amount of food consumed between the two groups trended toward significance (z = -1.63, p = 0.0516). The correlation of mPFC activity versus total IES in PPW was not significant (rs (7) = -0.412, p = 0.135). However, in NGW, correlation of mPFC activity and total IES was significant and positive (rs (15) = 0.414, p = 0.049). The correlation between IES score and food intake in PPW was significant (r (7) = -0.694, p = 0.019). However, there was no significant correlation between total IES and amount of food consumed in NGW (r (15) = -0.285, p = 0.134). For Experiment 2, there was a statistically significant, negative correlation between BMI and total IES (rs (66) = -0.238, p = 0.025) in NGW. There was no statistically significant relationships between total IES score and BMI in PPW (rs (60) = -0.172, p = 0.09). However, post hoc analyses revealed significant negative correlations between BMI and the individual IES subscales: unconditional permission to eat (r (62) = -0.336, p = 0.008), eating for physical rather than emotional reasons (r (62) = -0.311, p = 0.014), reliance on internal hunger and satiety cues (r (62) = -0.405, p = 0.001), and body-food choice congruence (r (62) = -0.277, p = 0.030) in PPW. Post-partum weight change was negatively correlated with the subscale measuring unconditional permission to eat in PPW who breastfeed (r (50) = -0.387, p = 0.006). Conclusions: Data from this study provides suggestions on the relationship between PFC activation and intuitive eating practices that differentially promote food overconsumption in PPW versus NGW. The negative relationship of mPFC during eating coupled with IES scores in PPW suggests a dependence on pleasure over satiety in determining food intake. Post hoc analyses revealed significant negative correlations between IES subscales and BMI in PPW. Additionally, post-partum weight change was negatively associated with the subscale measuring unconditional permission to eat in PPW who breastfeed. This finding suggests that PPW who breastfeed may experience a conflict between eating healthy to support breastfeeding and restricting eating to lose weight. Consequently, PPW who breastfeed may benefit from nutritional counseling to help them balance these conflicting needs. Development of weight loss/management interventions specifically targeted at PPW who breastfeed seem warranted.