Viscous placebo and carbohydrate breakfasts similarly decrease appetite and increase resistance exercise performance compared to a control breakfast in trained males

Given the common view that pre-exercise nutrition/breakfast is important for performance, the present study investigated whether breakfast influences resistance exercise performance via a physiological or psychological effect. Twenty-two resistance trained, breakfast-consuming men completed three experimental trials, consuming water-only (WAT), or semi-solid breakfasts containing 0 g/kg (PLA) or 1.5 g/kg (CHO) maltodextrin. PLA and CHO meals contained xanthan gum and low-energy flavouring (~29 kcal) and subjects were told both ‘contained energy’. Two hours post-meal, subjects completed 4 sets of back squat and bench press to failure at 90% 10 repetition maximum. Blood samples were taken pre-meal, 45 min and 105 min post-meal to measure serum/plasma glucose, insulin, ghrelin, GLP-1 and PYY concentrations. Subjective hunger/fullness were also measured. Total back squat repetitions were greater in CHO (44 (SD 10) repetitions) and PLA (43 ± 10 repetitions) than WAT (38 (SD 10) repetitions; P < 0.001). Total bench press repetitions were similar between trials (WAT 37 (SD 7) repetitions; CHO 39 ± 7 repetitions; PLA 38 (SD 7) repetitions; P = 0.130). Performance was similar between CHO and PLA trials. Hunger was suppressed and fullness increased similarly in PLA and CHO, relative to WAT (P < 0.001). During CHO, plasma glucose was elevated at 45 min (P < 0.05), whilst serum insulin was elevated (P < 0.05) and plasma ghrelin supressed at 45 and 105 min (P < 0.05). These results suggest that breakfast/pre-exercise nutrition enhances resistance exercise performance via a psychological effect, although a potential mediating role of hunger cannot be discounted

Training with low muscle glycogen enhances fat metabolism in well-trained cyclists

Purpose: To determine the effects of training with low muscle glycogen on exercise performance, substrate metabolism, and skeletal muscle adaptation. Methods: Fourteen well-trained cyclists were pair-matched and randomly assigned to HIGH-or LOW-glycogen training groups. Subjects performed nine aerobic training (AT; 90 min at 70% (V) over dotO(2max)) and nine high-intensity interval training sessions (HIT; 8 x 5-min efforts, 1-min recovery) during a 3-wk period. HIGH trained once daily, alternating between AT on day 1 and HIT the following day, whereas LOW trained twice every second day, first performing AT and then, 1 h later, performing HIT. Pretraining and posttraining measures were a resting muscle biopsy, metabolic measures during steady-state cycling, and a time trial. Results: Power output during HIT was 297 +/- 8 W in LOW compared with 323 +/- 9 W in HIGH (P < 0.05); however, time trial performance improved by similar to 10% in both groups (P < 0.05). Fat oxidation during steady-state cycling increased after training in LOW (from 26 +/- 2 to 34 +/- 2 mu mol.kg(-1).min(-1), P < 0.01). Plasma free fatty acid oxidation was similar before and after training in both groups, but muscle-derived triacylglycerol oxidation increased after training in LOW (from 16 +/- 1 to 23 +/- 1 mu mol.kg(-1).min(-1), P < 0.05). Training with low muscle glycogen also increased beta-hydroxyacyl-CoA-dehydrogenase protein content (P < 0.01). Conclusions: Training with low muscle glycogen reduced training intensity and, in performance, was no more effective than training with high muscle glycogen. However, fat oxidation was increased after training with low muscle glycogen, which may have been due to the enhanced metabolic adaptations in skeletal muscle

24-h severe energy restriction impairs postprandial glycaemic control in young, lean males

Intermittent energy restriction (IER) involves short periods of severe energy restriction interspersed with periods of adequate energy intake, and can induce weight loss. Insulin sensitivity is impaired by short-term, complete energy restriction, but the effects of IER are not well known. In randomised order, fourteen lean men (age: 25 (sd 4) years; BMI: 24 (sd 2) kg/m2; body fat: 17 (4) %) consumed 24-h diets providing 100 % (10 441 (sd 812) kJ; energy balance (EB)) or 25 % (2622 (sd 204) kJ; energy restriction (ER)) of estimated energy requirements, followed by an oral glucose tolerance test (OGTT; 75 g of glucose drink) after fasting overnight. Plasma/serum glucose, insulin, NEFA, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP) and fibroblast growth factor 21 (FGF21) were assessed before and after (0 h) each 24-h dietary intervention, and throughout the 2-h OGTT. Homoeostatic model assessment of insulin resistance (HOMA2-IR) assessed the fasted response and incremental AUC (iAUC) or total AUC (tAUC) were calculated during the OGTT. At 0 h, HOMA2-IR was 23 % lower after ER compared with EB (P<0·05). During the OGTT, serum glucose iAUC (P<0·001), serum insulin iAUC (P<0·05) and plasma NEFA tAUC (P<0·01) were greater during ER, but GLP-1 (P=0·161), GIP (P=0·473) and FGF21 (P=0·497) tAUC were similar between trials. These results demonstrate that severe energy restriction acutely impairs postprandial glycaemic control in lean men, despite reducing HOMA2-IR. Chronic intervention studies are required to elucidate the long-term effects of IER on indices of insulin sensitivity, particularly in the absence of weight loss

High-fat overfeeding impairs peripheral glucose metabolism and muscle microvascular eNOS Ser1177 phosphorylation.

CONTEXT: The mechanisms responsible for dietary fat-induced insulin resistance of skeletal muscle and its microvasculature are only partially understood. OBJECTIVE: To determine the impact of high-fat overfeeding on postprandial glucose fluxes, muscle insulin signaling, and muscle microvascular eNOS content and activation. DESIGN: Fifteen non-obese volunteers consumed a high-fat (64%) high-energy (+47%) diet for 7 days. Experiments were performed before and after the diet. Stable isotope tracers were used to determine glucose fluxes in response to carbohydrate plus protein ingestion. Muscle insulin signaling was determined as well as the content and activation state of muscle microvascular eNOS. RESULTS: High-fat overfeeding impaired postprandial glycemic control as demonstrated by higher concentrations of glucose (+11%; P = 0.004) and insulin (+19%; P = 0.035). Carbohydrate plus protein ingestion suppressed endogenous glucose production to a similar extent before and after the diet. Conversely, high-fat overfeeding reduced whole body glucose clearance (-16%; P = 0.021) and peripheral insulin sensitivity (-26%; P = 0.006). This occurred despite only minor alterations in skeletal muscle insulin signaling. High-fat overfeeding reduced eNOS content in terminal arterioles (P = 0.017) and abolished the increase in eNOS Ser1177 phosphorylation that was seen after carbohydrate plus protein ingestion. CONCLUSION: High-fat overfeeding impaired whole-body glycemic control due to reduced glucose clearance, not elevated endogenous glucose production. The finding that high-fat overfeeding abolished insulin-mediated eNOS Ser1177 phosphorylation in the terminal arterioles suggests that impairments in the vasodilatory capacity of the skeletal muscle microvasculature may contribute to early dietary fat-induced impairments in glycemic control

A 7-day high-fat, high-calorie diet induces fibre-specific increases in intramuscular triglyceride and perilipin protein expression in human skeletal muscle

KEY POINTS: We have recently shown that a high-fat high-calorie (HFHC) diet decreases whole body glucose clearance without impairing skeletal muscle insulin signalling, in healthy lean individuals. These diets are also known to increase skeletal muscle IMTG stores, but the effect on lipid metabolites leading to skeletal muscle insulin resistance has not been investigated. This study measured the effect of 7 days HFHC diet on: 1) skeletal muscle concentration of lipid metabolites, and 2) potential changes in the perilipin (PLIN) content of the lipid droplets (LD) storing IMTG. The HFHC diet increased PLIN3 protein expression and redistributed PLIN2 to LD stores in type I fibres. The HFHC diet increased IMTG content in type I fibres, while lipid metabolite concentrations remained the same. The data suggest that the increases in IMTG stores assists reducing the accumulation of lipid metabolites known to contribute to skeletal muscle insulin resistance. ABSTRACT: A HFHC diet reduces whole body glucose clearance without impairing skeletal muscle insulin signalling in healthy lean individuals. HFHC diets also increase skeletal muscle lipid stores. However, unlike certain lipid metabolites, intramuscular triglyceride (IMTG) stored within lipid droplets (LD) does not directly contribute to skeletal muscle insulin resistance. Increased expression of perilipin (PLIN) proteins and colocalisation to LD has been shown to assist in IMTG storage. We aimed to test the hypothesis that 7 days on a HFHC diet increases IMTG content while minimising accumulation of lipid metabolites known to disrupt skeletal muscle insulin signalling in sedentary and obese individuals. We also aimed to identify changes in expression and subcellular distribution of proteins involved in IMTG storage. Muscle biopsies were obtained from the m. vastus lateralis of 13 (n = 11 males, n = 2 females) healthy lean individuals (age: 23 ± 2.5 y, BMI: 24.5 ± 2.4 kg m-2 ), following an overnight fast, before and after consuming a high-fat (64% energy) high-calorie (+47% kcal) diet for 7 days. After the HFHC diet, IMTG content increased in type I fibres only (+10%; P < 0.001), whereas there was no change in the concentration of either total diacylglycerol (P = 0.123) or total ceramides (P = 0.150). Of the PLINs investigated, only PLIN3 content increased (+50%; P < 0.01) solely in type I fibres. LDs labelled with PLIN2 increased (80%; P < 0.01), also in type I fibres only. We propose that these adaptations to LD support IMTG storage and minimise accumulation of lipid metabolites to protect skeletal muscle insulin signalling following 7 days HFHC diet. This article is protected by copyright. All rights reserved

Leucine-enriched protein feeding does not impair exercise-induced free fatty acid availability and lipid oxidation: beneficial implications for training in carbohydrate-restricted states

Given that the enhanced oxidative adaptations observed when training in carbohydrate (CHO) restricted states are potentially regulated through free fatty acid (FFA) mediated signalling and that leucine rich protein elevates muscle protein synthesis, the present study aimed to test the hypothesis that leucine enriched protein feeding enhances circulating leucine concentration but does not impair FFA availability nor whole body lipid oxidation 56 during exercise. Nine males cycled for 2 h at 70% VO2peak when fasted (PLACEBO) or having consumed a whey protein solution (WHEY) or a leucine enriched whey protein gel (GEL), administered as 22 g 1 hour pre-exercise, 11 g/h during and 22 g thirty minutes post-exercise. Total leucine administration was 14.4 g and 6.3 in GEL and WHEY, respectively. Mean plasma leucine concentrations were elevated in GEL (P= 0.001) compared 60 with WHEY and PLACEBO (375 ± 100, 272 ± 51, 146 ± 14 μmol.L-1 respectively). No differences (P= 0.153) in plasma FFA (WHEY 0.53 ± 0.30, GEL 0.45 ± 0.25, PLACEBO 0.65 ± 0.30, mmol.L-1) or whole body lipid oxidation during exercise (WHEY 0.37 ± 0.26, GEL 0.36 ± 0.24, PLACEBO 0.34 ± 0.24 g/min) were apparent between trials, despite elevated (P= 0.001) insulin in WHEY and GEL compared with PLACEBO (38 ± 16, 35 ± 16, 22 ± 11 pmol.L-1 respectively). We conclude that leucine enriched protein feeding does not impair FFA availability nor whole body lipid oxidation during exercise, thus having practical applications for athletes who deliberately train in CHO restricted states to promote skeletal muscle adaptations

PAKs supplement improves immune status and body composition but not muscle strength in resistance trained individuals

Mixed formula supplements are very popular among recreational and professional weightlifters. They are usually known as PAKs and they are supposed to have a synergistic effect of their different nutrients. The purpose of this study was to determine the effects of chronic (4 weeks) PAKS supplementation in combination with strength training on body composition, immune status and performance measures in recreationally trained individuals with or without PAKs supplementation. Methods: Twelve male subjects (Placebo n = 6 and PAKs supplement n = 6) were recruited for this study. The body composition, one maximum strength repetition tests and immune status were assessed before and after 4 week supplementation. Our data showed that, 4 week PAK supplementation associated with strength exercise not was effective in change strength than compared with placebo group. However, we observed that, PAK supplement was able to improve immune status and reduced body composition when compared with placebo group. These results indicate that, a mixed formula supplement is able to improve immune status and body composition but not maximum strength in recreational strength trained subjects in a 4 weeks period

Young, healthy males and females present cardiometabolic protection against the detrimental effects of a 7-day high-fat high-calorie diet

Purpose: High-fat, high-calorie (HFHC) diets have been used as a model to investigate lipid-induced insulin resistance. Short-term HFHC diets reduce insulin sensitivity in young healthy males, but to date, no study has directly compared males and females to elucidate sex-specific differences in the effects of a HFHC diet on functional metabolic and cardiovascular outcomes. Methods: Eleven males (24 ± 4 years; BMI 23 ± 2 kg.m−2; V̇O2 peak 62.3 ± 8.7 ml.min−1.kg−1FFM) were matched to 10 females (25 ± 4 years; BMI 23 ± 2 kg.m−2; V̇O2 peak 58.2 ± 8.2 ml.min−1.kg−1FFM). Insulin sensitivity, measured via oral glucose tolerance test, metabolic flexibility, arterial stiffness, body composition and blood lipids and liver enzymes were measured before and after 7 days of a high-fat (65% energy) high-calorie (+ 50% kcal) diet. Results: The HFHC diet did not change measures of insulin sensitivity, metabolic flexibility or arterial stiffness in either sex. There was a trend towards increased total body fat mass (kg) after the HFHC diet (+ 1.8% and + 2.3% for males and females, respectively; P = 0.056). In contrast to females, males had a significant increase in trunk to leg fat mass ratio (+ 5.1%; P = 0.005). Conclusion: Lean, healthy young males and females appear to be protected from the negative cardio-metabolic effects of a 7-day HFHC diet. Future research should use a prolonged positive energy balance achieved via increased energy intake and reduced energy expenditure to exacerbate negative metabolic and cardiovascular functional outcomes to determine whether sex-specific differences exist under more metabolically challenging conditions