Military personnel and some athlete populations endure short-term energy deficits from reduced energy intake and/or increased energy expenditure (EE) that may degrade physical and cognitive performance due to severe hypoglycemia (<3.1 mmol/L). The extent to which energy deficits alter normoglycemia (3.9-7.8 mmol/L) in healthy individuals is not known since prior studies measured glucose infrequently, not continuously. Purpose: To characterize the glycemic response to acute, severe energy deficit compared to fully fed control condition, using continuous glucose monitoring (CGM). Methods: For 2 days during a double-blind, placebo-controlled, crossover study, 23 volunteers (17M/6F; age: 21.3±3.0 years; BMI: 25±3 kg/m2) increased habitual daily EE ([mean±SD] 2300±450 kcals/d) by 1647±345 kcals/d through prescribed exercise (~3 hr/d; 40-65% VO2peak), and consumed diets designed to maintain energy balance (FED) or induce 93% energy deficit (DEF). Interstitial glucose concentrations were measured continuously by CGM (Medtronic Minimed). Results: Interstitial glucose concentrations were 1.0±0.9 mmol/L lower during DEF versus FED (p<0.0001). The percentage of time spent in mild (3.1-3.8 mmol/L) hypoglycemia was higher during DEF compared to FED (mean difference = 20.5%, [95% CI: 13.1%, 27.9%], P=0.04), while time spent in severe (<3.1 mmol/L) hypoglycemia was not different between interventions (mean difference = 4.6% [95% CI: -0.6%, 9.8%], P=0.10). Three of 23 participants spontaneously reported symptoms (e.g., nausea) potentially related to hypoglycemia during DEF, and, an additional participant reported symptoms during both interventions. Conclusion: These findings suggest that severe hypoglycemia rarely occurs in healthy individuals enduring severe, short-term energy deficit secondary to heavy exercise and inadequate energy intake.
- caloric restriction
- interstitial glucose
- energy deficit
- continuous glucose measurement
- Copyright © 2016, Journal of Applied Physiology