Cliff J. d C. Harvey, Grant M. Schofield, Caryn Zinn, Simon J. ThornleyJournal of Holistic Performance ISSN: 2463-7238 | DOI: 10.26712/08102019 Published: 8 October 2019 Key findings in plain English:
Background
Low-carbohydrate diets are frequently used and are effective for improving a range of health outcomes. There is some evidence to suggest that certain individuals will achieve greater results from higher- or lower-carbohydrate diets but at this time there is little evidence to indicate the relative ‘appropriateness’ of diets differing in carbohydrate content for an individual. This study explores associations between baseline and changes in blood measures of cardiometabolic health, relative to carbohydrate allocation.
Methods
Seventy-seven healthy, non-diabetic participants (25 males, 52 females [mean age: 39 years, range: 25 to 49; mean body mass index (BMI) 27 kg/m2, range: 20-39]) participated in a 12-week, randomised, clinical intervention study. Participants completed baseline testing of blood measures and basic anthropometric measures and a lead-in week to identify habitual calorie intake. Participants were assigned to one of three low-carbohydrate diet plans which advised intakes of either 5%, 15%, or 25% of energy derived from carbohydrate, individualised to the participant and standardised for protein, at 1.4 g per kg of body weight (bw) per day. For the final nine weeks of the intervention they were advised to eat ad libitum but to adhere as closely as possible to the carbohydrate energy limit for their treatment group. Participants were instructed to continue habitual exercise patterns. Blood measures of cardiometabolic health (glucose, insulin, c-peptide, total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, triglycerides (TG)) and anthropometric measures (height, weight, and waist and hip girth) were measured at baseline and at the conclusion of the 12-week dietary intervention. The associations between baseline blood and anthropometric measures and the changes in these measures were made by undertaking multiple linear regression for the baseline measure and treatment group as independent variables with the change in outcome measures as dependent variables.
Results
There was a greater improvement in participants who had more adverse baseline cardiometabolic measures from a greater carbohydrate restriction, with 7 of 11 measures most benefiting from a very low carbohydrate ketogenic diet (VLCKD) intervention relative to baseline measurements. Only HDL cholesterol reached between-group significance, with every 1 mmol/L higher HDL cholesterol at baseline associated with a 0.5 and 0.2 mmol/L improvement in HDL cholesterol for the moderate-low carbohydrate diet and low-carbohydrate diet groups respectively, and a 0.4 mmol/L worsening for VLCKD (p = 0.0006).
Conclusions
Overall, there is a consistent association between baseline markers of cardiometabolic health and changes in these markers relative to the amount of carbohydrate included in the diet. However, low HDL cholesterol might be improved most by a moderate restriction of carbohydrate to ~25% of TE when compared to greater carbohydrate restriction. Because most results were not significant due to the small sample size and preliminary nature of this study, further research is required with larger cohorts to investigate this hypothesis further.
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 Baseline Cardiometabolic Markers Predict the Efficacy of Carbohydrate Restriction in Healthy Adults? A Pilot Study. Journal of Holistic Performance. October 2019. DOI: 10.26712/08102019
Cliff J. d C. Harvey, Grant M. Schofield, Caryn Zinn, Simon J. ThornleyJournal of Holistic Performance ISSN: 2463-7238 | DOI: 10.26712/072019 Published: 5 July 2019 Key findings in plain English:
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
Julia C. McPhee, Caryn Zinn, Melody Smith
Journal of Holistic Performance
ISSN: 2463-7238 | DOI: 10.26712/012018 Published: 23 January 2018 Key findings in plain English:
Background
It is well recognised that ageing in females is associated with a predilection for weight gain. Women with abdominal obesity are known to be at especially high risk of cardiovascular and metabolic disease, as well as associated poorer overall health outcomes. Many of these metabolic disorders, however, can be alleviated through weight loss.
Methods
This research describes an exploratory study investigating the self-reported acceptance of, and adherence to, a carbohydrate-restricted diet in women aged 40-55 years old. The 8-week weight loss dietary intervention was based on a whole food approach, which was lower in total carbohydrate and higher in dietary fat than mainstream nutrition guidelines. The two primary outcome measures of this research were barriers to and motivators for acceptance of and adherence to this way of eating. The mixed methods approach employed endorsed a multi-level intervention, integrating behaviour change models with both the medium of delivery and required dietary modifications.
Hypothesis
The hypothesis underpinning this study is that a lower carbohydrate, higher fat (LCHF) dietary approach, through its macronutrient profile, has the potential to enhance an individual’s self-reported adherence to behavioural lifestyle modifications required to reduce weight and improve metabolic health outcomes.
Results
Support by family members, in particular, spouses, was a key theme and appeared to act as both a barrier and motivator to adherence. Subsequent themes included satiety or feelings of fullness, being prepared by ensuring suitable food options were readily available, and acceptability of new food options.
Discussion
The findings from this study suggest self-reported adherence to this way of eating was achieved via improved satiety and enhanced social and spousal support. Moreover, results showed that for this population group, the intervention design was appropriate and medium of delivery was effective.
Authors
Julia C. McPhee
Human Potential Centre, Auckland University of Technology ORCID | Google Scholar Caryn Zinn Human Potential Centre, Auckland University of Technology ORCID | Google Scholar Melody Smith School of Nursing, Auckland University of Technology ORCID | Google Scholar Correspondence to: Julia McPhee julia.mcphee@aut.ac.nz Citation
McPhee JC, Zinn C, Smith M. Exploring the acceptability of, and adherence to a carbohydrate-restricted diet as self-reported by women aged 40-55 years. Journal of Holistic Performance. Jan 2018. DOI: 10.26712/012018
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