Female breakfast skippers display a disrupted cortisol rhythm and elevated blood pressure

Chronic stress and over-activity in the hypothalamic-pituitary-adrenal (HPA) axis may link breakfast skipping and poor cardiometabolic health. Missing the first major meal of the day in rodents prolongs elevated circulating corticosterone at a time when it's normally decreasing. To extend these findings to humans, we hypothesized that habitual breakfast skippers would display a similar pattern of circulating cortisol and alterations in meal and stress-induced cortisol reactions. Normal weight to obese women aged 18-45 years old who were strictly defined as either breakfast skippers (n=30) or breakfast eaters (n=35) were invited to participate in our study. Normal breakfast habits were maintained for the entire study period and each participant attended 4 lab visits. Over the first 2 lab visits, body composition, fasting clinical chemistries, and self-reports of chronic stress were assessed. On each of 2 additional days (lab visits 3 and 4), salivary free cortisol was measured at home upon waking and at bedtime, and in the lab in response to a standard lunch, ad libitum afternoon snack buffet, and stress and control (relaxation) tasks. The order of the control and stress test visits was randomized. While body weight, body composition, HOMA-IR, total and HDL cholesterol did not statistically differ (p>0.05), both diastolic and systolic blood pressure was elevated (p<0.01) and LDL cholesterol was lower (p=0.04) in the breakfast skipper group. Compared to the breakfast eaters and on the control task visit only, breakfast skippers had higher circulating cortisol from arrival to midafternoon (p<0.01) and during the snack buffet (p<0.05). Furthermore, the lunch-induced cortisol reaction was larger in the 'skippers' (p=0.03). On both stress and control visit days, the diurnal cortisol amplitude was significantly (p=0.02) blunted in breakfast skippers. Self-reports of chronic stress did not differ between the groups. These data indicate that habitually skipping breakfast is associated with stress-independent over-activity in the HPA axis which, if prolonged, may increase risk (e.g., hypertension) for cardiometabolic disease in some people.