Energy intake and season interact to influence physiological stress load among midlife women

Allostatic load (AL) is an index that measures physiologic stress associated with chronic disease risk. One factor that may influence overall physiologic stress load and AL is energy consumption, but whether this association differs across different seasons is unknown. We tested whether energy consumption interacted with the season to influence AL in 52 mid-life (40-60 years) women from the Life in All Seasons Study. Women completed an online 24-h recall every 10 days and had components of allostatic load measured seasonally. Women were from the greater Grand Forks, ND catchment area and were followed for one year between July 2012 and July 2014. We found a significant (p = 0.01) interaction between season and energy consumption on AL. Further inspection showed that, during the summer and winter seasons, the average allostatic load rose with relatively higher energy consumption. We also observed a linear and positive association between AL and energy intake in summer (β = 0.0013 ± 0.0004; p = 0.001; r² = 0.14) and winter (β = 0.0011 ± 0.0004; p = 0.007; r² = 0.10), but not in fall or spring. These results suggest that factors associated with distinct times of the year promote or prevent the effects of higher energy consumption on physiological stress load. Since allostatic load is linked to elevated disease risk, our results provide additional information that may help to explain seasonal differences in disease risk of some women.