20th Annual Sleep and Health Benefit

Reduced Daily Rhythm of Fractal Cardiac Dynamics Is Associated with Weight Loss Resistance in Overweight/Obese Women

Hui-Wen Yang, PhD

Brigham and Women's Hospital

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Clinical Implications
Research Narrative

Introduction: Weight loss in response to dietary interventions shows huge inter-individual variations, which cannot be explained by diet and exercise levels. A possible contributing factor is sleep/circadian regulation that may affect body weight and metabolism via its influences on autonomic function. Evidence indicates a delicate interplay between sympathetic and vagal outflows, generating fractal temporal correlations in heartbeat fluctuations that change with sleep/wake states and circadian phases. Here we tested whether the daily rhythm of fractal cardiac dynamics is linked to weight loss resistance, and whether the rhythm is altered in people carrying genetic variant CLOCK (Circadian Locomotor Output Cycles Kaput) 3111C allele who have increased weight loss resistance.

Methods: Forty overweight/obese Caucasian women (BMI>25) completed an obesity dietary treatment (up to 30 weeks) and a cardiac assessment in which heartbeat intervals were continuously recorded for ~3.5 days. The sample included 20 C carriers (CC and TC) and 20 non-carriers with matched age, BMI, energy intake, and physical activity levels. Fractal correlations in heartbeat fluctuations were quantified in each 1-h bin, and 24-h rhythmicity was estimated using cosinor analysis.

Results: Subjects lost 9.8%±0.9%[SE] of the initial weight during the treatment. There were more Low Responders (weigh loss 10% (0.150±0.012, 16% reduction, p<0.001), mainly due to increased trough alpha during the nighttime. Consistently, the amplitude was lower in C carriers than that of non-carriers (20% reduction, p<0.001).

Conclusion: Reduced daily rhythm of fractal cardiac dynamics is associated with higher weight loss resistance, which may mediate the influence of the CLOCK 3111T/C genetic variant on body weight control.


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