SAN FRANCISCO – Skipping breakfast triggered acute insulin resistance and elevated levels of free fatty acids in nine obese, nondiabetic women, compared with a day on which they ate breakfast in a randomized crossover trial.
If just 1 day of missing breakfast could do this, then skipping breakfast regularly over time may lead to further metabolic derangements, such as chronic insulin resistance and possible progression to type 2 diabetes mellitus, Dr. Elizabeth A. Thomas suggested.
The findings give clinicians one more tool to try to convince patients to eat a healthy breakfast, she said at the annual meeting of the Endocrine Society.
She and her associates studied the women on two separate days, approximately 1 month apart, and randomized them to receive breakfast or no breakfast at the first visit and the opposite at the second visit. They asked the women not to exercise prior to each visit and gave them a standardized dinner the night before the study day. Fasting laboratory measures were taken the morning of the study day, and 4 hours later, the participants were given a standardized lunch. The investigators took blood samples every 30 minutes after lunch for 3 hours and later gave them a standardized dinner.
Levels of insulin and glucose did not differ significantly between groups before lunch. Insulin and glucose levels were significantly higher after lunch on the days that the women skipped breakfast, representing acute insulin resistance, reported Dr. Thomas, an endocrinology fellow at the University of Colorado, Aurora.
Insulin levels rose significantly higher on the no-breakfast days, compared with after breakfast within 1 hour of the meal, and remained significantly higher at 2 hours. Similarly, the increase in glucose levels was significantly higher on the no-breakfast days within 1 hour of eating and remained significantly elevated, compared with levels on the breakfast days.
Free fatty acid levels were suppressed following breakfast, as would be expected, and thus were higher before lunch on days without breakfast. Both the total and incremental area under the curve (AUC) for free fatty acids after lunch were higher on the no-breakfast days, compared with breakfast days, suggesting that prelunch free fatty acid levels were not the cause of the increased AUC, she said.
Prelunch triglyceride levels were lower on no-breakfast days than on breakfast days. The total AUC for triglyceride levels after lunch was lower on no-breakfast days, compared with breakfast days, but the incremental AUC did not differ significantly between groups, suggesting that the prelunch triglyceride levels were driving the difference in total AUC, Dr. Thomas said.
Indirect calorimetry measures showed decreased energy expenditure on no-breakfast days and a significantly reduced respiratory quotient, which indicates greater fat oxidation, she said.
Previous epidemiologic and longitudinal studies have found associations between breakfast skipping and greater weight gain and risk for type 2 diabetes, but most of these were small studies focused on lean subjects, and none have shown a causal relationship, Dr. Thomas said. Few other short-term studies have assessed the effects of breakfast skipping on metabolic parameters and appetite.
In the study, the insulin total AUC was 12,322 microIU/mL x 180 minutes on no-breakfast days, compared with 8,882 microIU/mL x 180 minutes on breakfast days. The glucose total AUC was 20,775 vs. 18,126 mg/dL x 180 minutes on no-breakfast and breakfast days, respectively.
Prelunch free fatty acid levels on no-breakfast and breakfast days, respectively, were 705 vs. 287 microEq/L, and the total AUC for free fatty acids was 33,980 vs. 25,692 microEq/L x 180 minutes. The incremental AUC for free fatty acids was –92,980 vs. –26,008 microEq/L x 180 minutes. Prelunch triglyceride levels were 86 vs. 121 mg/dL on no-breakfast and breakfast days, respectively. The triglyceride total AUC was 17,352 vs. 24,060 mg/dL x 180 minutes on days without and with breakfast, respectively.
The women had a mean age of 29 years and a mean body mass index of 31 kg/m2. Eight women said that they habitually eat breakfast. Dr. Thomas hopes to expand the study to 20 women and to include more women who habitually skip breakfast. She also plans to control for exercise in a future study.
The medical literature reports that roughly 10%-20% of Americans routinely skip breakfast, she said. Dr. Lisa Fish of the University of Minnesota, Minneapolis, who moderated a press briefing on Dr. Thomas’s study, said that many American breakfasts are high in carbohydrates and low in protein, and that eating a more balanced meal at the start of the day would be healthier.