A pre-lunch 30-min bout of aerobic exercise did not increase the 24-h risk of hypoglycaemia post-metabolic/bariatric surgery but elevated post-MMTT glucose levels.
Key Findings
Results
Only one isolated hypoglycaemic event occurred across both conditions, precluding statistical analysis of the primary outcome.
The primary outcome was time spent with glucose <3.0 mmol/L during the 24-h post-intervention
Only one isolated hypoglycaemic event (<3.0 mmol/L) occurred across all participants and conditions
CGM data were available for analysis in 11 of 15 enrolled participants
The extremely low incidence of hypoglycaemia made formal statistical comparison between conditions impossible
Results
Mean 24-hour glucose levels did not differ significantly between the aerobic exercise and control conditions.
Mean 24-h glucose: AEX 6.4 (1.0) mmol/L vs CON 6.5 (0.9) mmol/L
No statistically significant difference between conditions (p = 0.57)
Time with glucose <3.9 mmol/L: AEX 0 (0.0, 0.5)% vs CON 0 (0.0, 0.5)%; p = 0.68
Results suggest a single pre-lunch bout of moderate aerobic exercise does not worsen 24-h glucose control
Results
Aerobic exercise significantly reduced glucose coefficient of variation during the 24-hour post-intervention period.
Glucose coefficient of variation was lower following AEX compared to CON (p < 0.01)
This indicates reduced glycaemic variability in the exercise condition
This was a secondary CGM-derived glucose metric outcome
Results
Aerobic exercise elevated glucose and insulin responses during the 3-hour mixed-meal tolerance test (MMTT).
Nadir glucose during MMTT was higher following AEX (p < 0.05)
Peak glucose during MMTT was higher following AEX (p < 0.05)
AUC0-180 glucose during MMTT was higher following AEX (p < 0.05)
Pre-MMTT insulin concentrations were higher following AEX (all p < 0.05)
The MMTT was administered as a standardised lunch immediately after the AEX or CON condition
Methods
The study used a randomised crossover design in which participants after metabolic/bariatric surgery performed 30 minutes of treadmill walking at 60% VO2peak or time-matched sitting.
15 participants without diabetes who had undergone metabolic/bariatric surgery were enrolled
Participants completed both conditions (AEX and CON) in a crossover design
Exercise consisted of 30 minutes of treadmill walking at 60% VO2peak
Both conditions were preceded by an overnight fast and a standardised breakfast, and followed by an identical standardised lunch as a MMTT
Continuous glucose monitoring assessed glucose levels for 24 hours post-intervention, during which participants consumed standardised meals
What This Means
This research suggests that a single 30-minute session of moderate-intensity walking performed before lunch does not increase the risk of low blood sugar (hypoglycaemia) in people who have had weight-loss (bariatric) surgery. Hypoglycaemia after bariatric surgery is a known concern, as the procedure can cause exaggerated insulin responses after eating, potentially causing blood sugar to drop too low. In this small study, hypoglycaemia was extremely rare — only one episode occurred across all participants and sessions — meaning the researchers could not statistically compare hypoglycaemia rates between the exercise and resting conditions.
Interestingly, exercise actually led to higher blood sugar levels during the meal test that followed, along with higher insulin levels before the meal. This may reflect that exercise temporarily raised blood sugar and prompted the body to release more insulin in preparation for eating. Despite this, over the full 24 hours after exercise, average blood sugar levels and time spent with low glucose were similar to resting, and glucose variability was actually reduced with exercise.
This research suggests that moderate aerobic exercise before a meal appears to be safe for people after bariatric surgery and does not appear to trigger dangerous drops in blood sugar. However, the study was small and conducted under very controlled conditions, so further research in larger and more diverse groups under everyday conditions is needed before broad recommendations can be made.
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Podesta-Donoso I, Papamargaritis D, Henson J, Katsarova-Harrison S, Tziannou A, Waller H, et al.. (2026). The Effect of Acute Aerobic Exercise On the Time Spent in Hypoglycaemia After Bariatric Surgery (The BariEX Study).. Obesity surgery. https://doi.org/10.1007/s11695-026-08712-3