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Can a ‘Carbohydrate Tolerance Questionnaire’ Predict Outcomes from Diets Differing in Carbohydrate Content? A Pilot Study

5/7/2019

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Cliff J. d C. Harvey, Grant M. Schofield, Caryn Zinn, Simon J. Thornley


​Journal of Holistic Performance
ISSN: 2463-7238 | DOI: 10.26712/072019
Published: 5 July 2019

Key findings in plain English:
  • People who score more poorly on a 'Carbohydrate Tolerance Questionnaire' are more likely to benefit from low-carbohydrate diets for improving triglyceride levels.
  • Those who are more 'carbohydrate intolerant' at baseline are also more likely to experience mood disturbance and greater symptoms of carbohydrate withdrawal (often called 'keto-flu').
  • The questionnaire might be useful for clinicians to allocate those who are less carb-tolerant to more moderate carbohydrate diets (compared to aggressive carbohydrate restriction).
  • Due to the lack of clear differences between groups, it is unclear whether the questionnaire can aid the allocation of different diets to improve cardiometabolic outcomes.
​
Clinical Trial | Peer-Reviewed
Can a Carbohydrate Tolerance Questionnaire...Harvey et al. 2019
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  • Abstract
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Background

Clinical trials and experience suggest that there is a wide variation in how people respond to different dietary protocols. Clinical experience suggests that there are common signs of relative carbohydrate ‘tolerance’ that might predict cardiometabolic and anthropometric outcomes resulting from differing diets and the optimal allocation of carbohydrate restriction that might be most suited to the individual.
​We believed that people with a higher carbohydrate intolerance score (CIS) determined from completing a carbohydrate tolerance questionnaire (CTQ) would achieve larger changes in cardiometabolic and anthropometric measures of health from greater magnitudes of carbohydrate restriction.
​

Methods

​Seventy-seven healthy participants were randomised to a very low carbohydrate ketogenic diet (VLCKD), low-carbohydrate diet (LCD), or moderate-low carbohydrate diet (MCD), containing 5%, 15% and 25% total energy from carbohydrate respectively, for 12-weeks. Anthropometric and metabolic health measures were taken at baseline and 12 weeks, and symptoms of carbohydrate withdrawal and mood evaluated by questionnaires. The association between CIS and changes in anthropometric and cardiometabolic markers and mood and symptoms of carbohydrate withdrawal were made by undertaking multiple linear regression. Differences between beta coefficients describing the outcome - CIS relationship by group were determined by an interaction term, testing for significance at a p-value < 0.05.
​

Results

Baseline carbohydrate tolerance was associated with improvement in serum triglycerides (TG) overall, (Beta = -0.025, p = 0.073) and in the VLCKD group (Beta = -0.034, p = 0.055). The only CIS-outcome relationship to vary significantly between groups was for change in body mass index (BMI); p = 0.007, with higher carbohydrate intolerance inversely associated with the change in BMI in the MCD group (Beta = -0.309, p = 0.032). Higher CIS was also associated with more severe symptoms of carbohydrate withdrawal (Beta = 0.214, p = 0.084) and increased mood disturbance (Beta = 0.044, p = 0.060). There was also a weak association between CIS and mood disturbance in the VLCKD group (Beta = 0.083, p = 0.014).
​

Conclusions

Our findings demonstrate that those with higher CIS are more likely to benefit from low-carbohydrate diets for the improvement of triglyceride concentrations. Subjects with higher scores are also more likely to experience mood disturbance and symptoms of carbohydrate withdrawal. The questionnaire might be useful for clinicians to allocate those with the highest CIS to a more moderately restricted plan to mitigate symptoms of carbohydrate withdrawal and effects on mood and to offer greater improvements in BMI. However, at this time and contrary to our hypothesis, due to the lack of clear between-group significance, it is unclear whether it can accurately predict the efficacy of dietary allocations for the individual.

Authors

Cliff J. d. C. Harvey
ORCID | Google Scholar

Grant M. Schofield
ORCID | Google Scholar

Caryn Zinn
​ORCID | Google Scholar

Simon J. Thornley

​ORCID | Google Scholar

All authors: Human Potential Centre, Auckland University of Technology.

Correspondence to: Dr Cliff Harvey  cliff@hpn.ac.nz 
​

Citation

Harvey CJ, Schofield GM, Zinn C, Thornley SJ. Can a ‘Carbohydrate Tolerance Questionnaire’ Predict Outcomes from Diets Differing in Carbohydrate Content? A Pilot Study. Journal of Holistic Performance. July 2019. DOI: 10.26712/05072019
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