Effects Of High-fat Diet And Exercise On Total Plasma Macronutrient Contents By Fourier-transform Infrared Spectroscopy

Abstract

High fat-low carbohydrate (HFLC) diets are increasingly considered by endurance athletes to enhance their performances and overall health. Total macronutrient contents in plasma may be affected by diets and exercise. PURPOSE: To examine the effects of HFLC diet and an acute bout of exercise on total plasma macronutrient contents in trained males. METHODS: Eight trained distance runners (age = 39.5±9.9 years and VO2max = 47.9±7.6 mL/kg/min) that were on high-carbohydrate (HC) diets adopted the HFLC diet for 3 weeks, which consisted of 70% of overall caloric intake from fats and no more than 50g of carbohydrates. At the end of each diet trial, participants performed an indoor treadmill exercise for 50 minutes at varying race paces followed by an outdoor 5-km time trial. Overnight fasting blood samples were collected at pre- (baseline) and post-exercise (24-hours) to analyze changes in total plasma lipids, proteins, and carbohydrates using attenuated total reflectance Fourier-transform infrared spectroscopy (ATR FT-IR). The O-H stretch vibrational band of water was used to normalize the IR spectra and the protein content was quantified by measuring the amide I peak intensity at 1600 - 1700 cm-1. To quantify the lipids and carbohydrates, the samples were lyophilized and measured by the intensities at 2800 - 3000 cm-1 and 800 - 1200 cm-1, respectively. RESULTS: The ATR FT-IR analysis showed that total plasma proteins remained unchanged (HC baseline = 135.20±4.20 and HFLC baseline = 135.24±3.91AU). However, the HC diet at baseline showed a significant accumulation of lipids (30.06±7.75 AU, 95% CI = 6.93) and carbohydrates (42.92±11.62 AU, 95% CI = 10.39). Additionally, total lipids in the HC diet significantly decreased at 24-hours post-exercise (from 30.06±7.75 to 28.51±7.91 AU, p=0.016). CONCLUSION: A short-term high-fat diet does not significantly alter any macronutrient contents in plasma, whereas a high-carbohydrate diet increases an accumulation of lipids and carbohydrates. Elevated plasma lipids and carbohydrates with a high-carbohydrate diet may be due to decreased insulin sensitivity, which consequently led to increased plasma lipid contents. Notably, decreased total plasma lipid content following an acute bout of exercise suggests that lipids were the primary energy substrate.