Key result
A low-energy diet high in fiber and coffee did not differ from a low-fiber, high-red-meat diet in improving heart rate variability over 8 weeks, though both reduced heart rate by 4-6 bpm.
Why the study?
Does a low-energy diet high in cereal fiber, free of red meat, and high in coffee improve cardiac autonomic function compared to a diet low in fiber, high in red meat, and coffee free in obese patients with type 2 diabetes?
RCT (n=28)
parallel-group
Does a low-energy diet high in cereal fiber, free of red meat, and high in coffee improve cardiac autonomic function compared to a diet low in fiber, high in red meat, and coffee free in obese patients with type 2 diabetes?
Energy restriction per se over 8 weeks improves cardiac vagal function in obese patients with type 2 diabetes, independent of dietary fiber, red meat, and coffee content.
OBJECTIVE: The autonomic nervous system (ANS) regulates both the cardiovascular system and energy balance and is disturbed in diabetes and obesity. The effect of different approaches of caloric restriction on ANS function has not been assessed in individuals with diabetes. Thus, we sought to determine whether low-energy diets differing in fiber, red meat, and coffee intake exert differential effects on cardiac autonomic function. RESEARCH DESIGN AND METHODS: In this randomized parallel-group pilot trial, obese patients with type 2 diabetes were randomly allocated to consume either a diet high in cereal fiber, free of red meat, and high in coffee (n = 13) or a diet low in fiber, high in red meat, and coffee free (n = 15) over 8 weeks. Eight measures of heart rate variability (HRV) indicating vagal and/or sympathetic modulation over 3 h and inflammatory markers were determined during a hyperinsulinemic-euglycemic clamp. RESULTS: After 8 weeks, both dietary interventions resulted in a mean weight loss of 5-6 kg, a mean decline in heart rate of 4-6 bpm, and improvement in vagally mediated HRV. However, the changes in HRV parameters from baseline to 8 weeks did not differ between the groups. In the entire study cohort, incremental HRV from baseline to 8 weeks was associated with enhanced oxidative glucose utilization (P < 0.05), but not with insulin sensitivity and inflammatory markers. CONCLUSIONS: In obese patients with type 2 diabetes, energy restriction per se over 8 weeks contributed to improved cardiac vagal function in relation to improved oxidative glucose utilization. This preliminary finding should be verified in a confirmatory trial.
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Ziegler et al. (2015) conducted an RCT in Obese with type 2 diabetes (n=28). Low-energy diet high in cereal fiber, free of red meat, and high in coffee vs. Low-energy diet low in fiber, high in red meat, and coffee free was evaluated on Changes in heart rate variability (HRV) parameters from baseline to 8 weeks. A low-energy diet high in fiber and coffee did not differ from a low-fiber, high-red-meat diet in improving heart rate variability over 8 weeks, though both reduced heart rate by 4-6 bpm.
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