Impact of COVID-19 restrictions and their relaxation on body composition and glycemic control in individuals with glucose intolerance in Japan: A single-center observational study.
Kobayashi A, Keidai Y, et al. • Journal of diabetes investigation • 2026
HbA1c levels gradually increased with a significant elevation post-SOE compared to pre-SOE, while skeletal muscle mass decreased progressively across all periods, clarifying the long-term metabolic effects of COVID-19 restrictions in individuals with glucose intolerance.
Key Findings
Results
HbA1c levels gradually increased across the study periods, with a significant elevation in the post-SOE period compared to pre-SOE.
The study assessed three time periods: pre-SOE (2019), SOE (2020-2021), and post-SOE (2023)
221 outpatients with glucose intolerance who had complete data for HbA1c and body composition in all three periods were included
The increase in HbA1c was statistically significant when comparing the post-SOE period to the pre-SOE period
Japan's COVID-19 restrictions included voluntary-based restrictions under a state of emergency from 2020 to 2021, with nationwide behavioral restrictions ending in May 2023 when COVID-19 received category 5 status
Results
Body weight and BMI remained stable during the SOE period but both decreased in the post-SOE period.
Study population was 221 outpatients with glucose intolerance
Body weight and BMI showed no significant change during the SOE (2020-2021)
Both body weight and BMI decreased following relaxation of restrictions in the post-SOE period (2023)
This pattern suggests differential metabolic responses to restriction versus relaxation phases
Results
Fat mass increased during the SOE period and subsequently decreased post-SOE, while skeletal muscle mass decreased progressively across all three periods.
Fat mass showed a bidirectional pattern: increasing during the SOE and then decreasing post-SOE
Skeletal muscle mass showed a unidirectional progressive decline across all three time periods (pre-SOE, SOE, and post-SOE)
The progressive loss of skeletal muscle mass occurred even as other body composition measures partially recovered post-SOE
These changes in body composition occurred in outpatients with glucose intolerance assessed across approximately four years
Results
Among the 68 individuals whose HbA1c worsened during the SOE, 25 experienced further deterioration post-SOE while 43 showed improvements in both glycemic control and body composition.
68 of 221 total participants (approximately 31%) experienced HbA1c worsening during the SOE period
25 of the 68 (approximately 37%) showed continued HbA1c deterioration in the post-SOE period
43 of the 68 (approximately 63%) showed improvements in both glycemic control and body composition post-SOE
This subgroup analysis formed the basis of the exploratory clustering analysis of behavioral patterns
Results
Clustering analysis of questionnaire responses in the HbA1c-worsened subgroup identified two distinct behavioral patterns associated with differential post-SOE HbA1c outcomes.
Lifestyle changes were evaluated using a questionnaire administered at the post-SOE period
Clustering analysis was performed on the 68 individuals whose HbA1c worsened during the SOE
One cluster was characterized by the combination of persistent reductions in physical activity and increased snacking
The cluster marked by persistent reductions in physical activity and increased snacking showed greater post-SOE HbA1c increases compared to the other cluster
The authors describe this as an 'exploratory analysis' and note that behavioral patterns were associated with post-SOE HbA1c changes
Methods
This was a single-center observational study of outpatients with glucose intolerance in Japan, evaluating metabolic and behavioral changes across pre-SOE, SOE, and post-SOE periods.
Study design was a single-center observational study
Participants were outpatients with glucose intolerance (GI) who had complete data for HbA1c and body composition in all three periods
Total sample size was 221 participants
Outcome measures included glycated hemoglobin (HbA1c), body composition (body weight, BMI, fat mass, skeletal muscle mass), and lifestyle behaviors via questionnaire
The study period spanned from 2019 to 2023, covering pre-pandemic through post-restriction phases in Japan
What This Means
This research suggests that the COVID-19 pandemic and its associated restrictions had lasting negative effects on blood sugar control and muscle mass in Japanese patients who already had impaired glucose regulation (a condition that can precede or include type 2 diabetes). Studying 221 outpatients across four years — before, during, and after Japan's COVID-19 emergency restrictions — the researchers found that blood sugar levels (measured by HbA1c) worsened progressively, with the most significant rise seen after restrictions were lifted in 2023. Notably, muscle mass declined continuously throughout the entire study period without recovering, even as body weight and fat mass partially improved after restrictions ended.
The study also found important variation among patients whose blood sugar worsened during the restriction period. About one-third of all participants saw their HbA1c rise during the restrictions, and of those, roughly 37% continued to worsen afterward while the majority improved. When researchers analyzed questionnaire responses about lifestyle habits, they identified two behavioral patterns: one group that maintained persistent reductions in physical activity combined with increased snacking continued to see worse blood sugar control after restrictions lifted, while those without this combination tended to recover.
This research suggests that the health impacts of pandemic-era lifestyle disruptions were not simply reversed when restrictions ended, particularly for individuals already at metabolic risk. The progressive and unrecovered loss of muscle mass is notable, as is the finding that specific behavioral combinations — reduced exercise paired with increased snacking — may identify individuals at higher risk for continued metabolic deterioration. These findings highlight the potential value of targeted lifestyle support for at-risk patients both during and after periods of societal disruption.
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Kobayashi A, Keidai Y, Murakami T, Tsukaguchi R, Fujita M, Wada K, et al.. (2026). Impact of COVID-19 restrictions and their relaxation on body composition and glycemic control in individuals with glucose intolerance in Japan: A single-center observational study.. Journal of diabetes investigation. https://doi.org/10.1111/jdi.70307