Post Meal Exercise May Lead to Transient Hypoglycemia Irrespective of Glycemic Status in Humans

Abstract

During exercise, there is coordination between various hormonal systems to ensure glucoregulation. This study examined if hypoglycemia occurs during moderate-intensity exercise in non-obese and obese individuals with and without type 2 diabetes (T2D). Eighteen non-obese, 18 obese, and 10 obese with T2D completed 2 study days that included a meal at 1,800 h followed by rest (NOEX) or exercise (PMEX; 45 min/55% of VO 2 max 2 h post meal). Glucose, insulin, and glucagon concentrations were measured throughout this 5.5 h period. Subjects with T2D had elevated glucose responses to the meal on both study days, compared to non-obese and obese subjects ( P < 0.05). During evening exercise (PMEX), subjects with T2D had a greater drop in glucose concentration (−98.4 ± 13.3 mg/dL) compared to obese (−44.8 ± 7.1 mg/dL) and non-obese (−39.3 ± 6.1 mg/dL; P < 0.01) subjects. Glucose levels decreased more so in females than males in both conditions ( P < 0.01). Nadir glucose levels <70 mg/dL were observed in 33 subjects during NOEX and 39 subjects during PMEX. Obese males had a larger exercise-induced insulin drop than obese females ( P = 0.01). During PMEX, peak glucagon concentrations were elevated compared to NOEX ( P < 0.001). Male participants with T2D had an increased glucagon response during NOEX and PMEX compared to females ( P < 0.01). In conclusion, in individuals with varying glucose tolerance, there is a dramatic drop in glucose levels during moderate-intensity exercise, despite appropriate insulin concentrations prior to exercise, and glucagon levels rising during exercise. Moderate-intensity exercise can result in low glucose concentrations (<60 mg/dL), and yet many of these individuals will be asymptomatic.

Association between pre‐exercise food ingestion timing and reactive hypoglycemia: Insights from a large database of continuous glucose monitoring data

“…The reason for the occurrence of hypoglycemia in a fasted state may be a result of: a subset of individuals with low glucose concentrations (Tanaka et al, 2021); situations in which glucose levels may be unable to be maintained (the net output of glycogenolysis and gluconeogenesis cannot match glucose utilization); situations in which this could occur include prolonged exercise even at low intensity, or higher intensity shorter duration exercise; and instances of high glucose levels as a result of intense exercise may drive a level of insulin release which when combined with insulin‐independent glucose uptake and cessation of exercise may drive a physiological process not dissimilar to rebound or reactive hypoglycaemia. Porter and colleagues (2020) reported an even higher % of individuals experiencing hypoglycemia. In their study, 94% (17 in 18) of the tested individuals experienced reactive hypoglycemia (<70 mg/dL) during a 45‐minute‐long exercise.…”

“…There is no consistency between the fractions reported by Kondo et al (2019) or Moseley et al (2003) or Porter et al (2020). The paucity of information regarding the single individual responses to different pre-exercise food ingestion timing, and the reduced sample sizes, the different quality/quantity of CHO ingested, the different performance levels of the participants, makes the estimation of this percentage rather speculative and poorly generalizable to free-living conditions.…”

“…Whether this can be a good estimate of the percentage of individuals susceptible to reactive hypoglycemia is yet to be established. In fact, in most of the studies investigating the effects of pre‐exercise food ingestion timing on blood glucose concentration (Kondo et al, 2019; Kuipers et al, 1999; Moseley et al, 2003; Porter et al, 2020), results have been presented only with sample averages, without stressing the highly individual nature of reactive hypoglycemia (Burdon et al, 2017). Furthermore, whether manipulating pre‐exercise food ingestion timing can be effective on all the individuals susceptible to reactive hypoglycemia is yet to be confirmed.…”

Is There an Optimal Time of Day for Exercise? A Commentary on When to Exercise for People Living With Type 1 or Type 2 Diabetes

“…For individuals with type 1 diabetes, performing light to moderate postmeal exercise (e.g., walking for 15–30 minutes) may be beneficial from a glucose-lowering perspective ( 38 – 40 ). However, if postmeal exercise extends beyond 30 minutes, hypoglycemia can often occur ( 41 , 42 ). On the other hand, if high amounts of protein or fat are consumed in a meal, the time to peak blood glucose can be delayed, leading to rebound hyperglycemia after exercise ( 43 ).…”