Effect of a Low-Carbohydrate High-Fat Diet and a Single Bout of Exercise on Glucose Tolerance, Lipid Profile and Endothelial Function in Normal Weight Young Healthy Females.

Thorhildur Ditta Valsdottir,Nancy Odden,Birgitte Nellemann,Ane C Westerberg,Jørgen Jensen,Per B Jeppesen,Jonny Hisdal,Christine Henriksen

doi:10.3389/fphys.2019.01499

Abstract

Low-carbohydrate-high-fat (LCHF) diets are efficient for weight loss, and are also used by healthy people to maintain bodyweight. The main aim of this study was to investigate the effect of 3-week energy-balanced LCHF-diet, with >75 percentage energy (E%) from fat, on glucose tolerance and lipid profile in normal weight, young, healthy women. The second aim of the study was to investigate if a bout of exercise would prevent any negative effect of LCHF-diet on glucose tolerance. Seventeen females participated, age 23.5 ± 0.5 years; body mass index 21.0 ± 0.4 kg/m2, with a mean dietary intake of 78 ± 1 E% fat, 19 ± 1 E% protein and 3 ± 0 E% carbohydrates. Measurements were performed at baseline and post-intervention. Fasting glucose decreased from 4.7 ± 0.1 to 4.4 mmol/L (p < 0.001) during the dietary intervention whereas fasting insulin was unaffected. Glucose area under the curve (AUC) and insulin AUC did not change during an OGTT after the intervention. Before the intervention, a bout of aerobic exercise reduced fasting glucose (4.4 ± 0.1 mmol/L, p < 0.001) and glucose AUC (739 ± 41 to 661 ± 25, p = 0.008) during OGTT the following morning. After the intervention, exercise did not reduce fasting glucose the following morning, and glucose AUC during an OGTT increased compared to the day before (789 ± 43 to 889 ± 40 mmol/L∙120min–1, p = 0.001). AUC for insulin was unaffected. The dietary intervention increased total cholesterol (p < 0.001), low-density lipoprotein (p ≤ 0.001), high-density lipoprotein (p = 0.011), triglycerides (p = 0.035), and free fatty acids (p = 0.021). In conclusion, 3-week LCHF-diet reduced fasting glucose, while glucose tolerance was unaffected. A bout of exercise post-intervention did not decrease AUC glucose as it did at baseline. Total cholesterol increased, mainly due to increments in low-density lipoprotein. LCHF-diets should be further evaluated and carefully considered for healthy individuals.

Highlights

There have been concerns that low-carbohydrate high-fat (LCHF) diets may increase the risk of cardiovascular disease (CVD) due to the increased intake of dietary fats (Mansoor et al, 2016b), as saturated fat has been linked to higher levels of low-density lipoprotein (LDL) with increased vascular dysfunction (Vogel et al, 1997; Mensink et al, 2003; Kim et al, 2005; Grasgruber et al, 2016; Chiu et al, 2017; Lambert et al, 2017; Durrer et al, 2019)
Glucose and Insulin Our results indicate that the overall metabolic regulation of glucose and insulin after one glucose load was not affected by the LCHF diet
The results demonstrate that the positive effect of an acute bout of endurance exercise seen prior to the intervention was blunted after a bout of exercise, after the LCHF diet

Summary

Introduction

Studies have shown that a low-carbohydrate high-fat (LCHF) diet can be a successful weight-loss tool for overweight and obese individuals (Perez-Guisado et al, 2008; Foster et al, 2010; Bueno et al, 2013; Gu et al, 2013; Bazzano et al, 2014; Moreno et al, 2014) and people with metabolic syndrome or type 2 diabetes (Tay et al, 2015; Steckhan et al, 2016). LCHF diets have resulted in favorable changes in triglycerides (TG) (Bazzano et al, 2014; Saslow et al, 2017) and high-density lipoprotein (HDL) in obese individuals (Bazzano et al, 2014; Moreno et al, 2014). Diets high in fat have been linked to disturbance in gut microbiota with increased gut permeability and inflammation (Murphy et al, 2015; SantosMarcos et al, 2019)

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