Effects of carbohydrate availability on sustained shivering II. Relating muscle recruitment to fuel selection

2004 ◽  
Vol 96 (1) ◽  
pp. 41-49 ◽  
Author(s):  
François Haman ◽  
Stéphane R. Legault ◽  
Mark Rakobowchuk ◽  
Michel B. Ducharme ◽  
Jean-Michel Weber
Keyword(s):  
Voluntary Contraction ◽  
Whole Body ◽  
Carbohydrate Diet ◽  
Adult Men ◽  
Low Carbohydrate Diet ◽  
Fuel Metabolism ◽  
Relative Contribution ◽  
Fuel Selection ◽  
Low Carbohydrate ◽  
Fuel Mixtures

The purpose of this study was to quantify how shivering activity would be affected by large changes in fuel metabolism (see Haman F, Peronnet F, Kenny GP, Doucet E, Massicotte D, Lavoie C, and Weber J-M, J Appl Physiol 96: 000–000, 2004). Adult men were exposed to 10°C for 2 h after a low-carbohydrate diet and exercise (Lo) and after high-carbohydrate diet without exercise (Hi). Using simultaneous metabolic and electromyographic (EMG) measurements, we quantified the effects of changes in fuel selection on the shivering activity of eight large muscles representing >90% of total shivering muscle mass. Contrary to expectation, drastic changes in fuel metabolism [carbohydrates 28 vs. 65% of total heat production (Ḣprod), lipids 53 vs. 23% Ḣprod, and proteins 19 vs. 12% Ḣprod for Lo and Hi, respectively] are achieved without altering the EMG signature of shivering muscles. Results show that total shivering activity and the specific contribution of each muscle to total shivering activity are not affected by large changes in fuel selection. In addition, we found that changes in burst shivering rate (∼4 bursts/min), relative contribution of burst activity to total shivering (∼10% of total shivering activity), and burst shivering intensity (∼12% of maximal voluntary contraction) are the same between Lo and Hi. Spectral analysis of EMG signals also reveals that mean frequencies of the power spectrum remained the same under all conditions (whole body average of 78 ± 5 Hz for Lo and 83 ± 7 Hz for Hi). During low-intensity shivering, humans are therefore able to sustain the same thermogenic rate by oxidizing widely different fuel mixtures within the same muscle fibers.

scholarly journals Beneficial Effects of an 8-Week, Very Low Carbohydrate Diet Intervention on Obese Subjects

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Yunjuan Gu ◽  
Haoyong Yu ◽  
Yuehua Li ◽  
Xiaojing Ma ◽  
Junxi Lu ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Weight Loss ◽  
Body Composition ◽  
Metabolic Profile ◽  
Whole Body ◽  
Carbohydrate Diet ◽  
Beneficial Effects ◽  
Low Carbohydrate Diet ◽  
Low Carbohydrate ◽  
Obese Subjects

Aim. To investigate the effects of weight loss during an 8-week very low carbohydrate diet (VLCD) on improvement of metabolic parameters, adipose distribution and body composition, and insulin resistance and sensitivity in Chinese obese subjects.Methods. Fifty-three healthy obese volunteers were given an 8-week VLCD. The outcomes were changes in anthropometry, body composition, metabolic profile, abdominal fat distribution, liver fat percent (LFP), and insulin resistance and sensitivity.Results. A total of 46 (86.8%) obese subjects completed the study. The VLCD caused a weight loss of−8.7±0.6 kg (mean ± standard error (SE),P<0.0001) combined with a significant improvement of metabolic profile. In both male and female, nonesterified fatty acid (NEFA) significantly decreased (−166.2±47.6 μmol/L,P=0.001) andβ-hydroxybutyric acid (BHA) increased (0.15±0.06 mmol/L,P=0.004) after eight weeks of VLCD intervention. The significant reductions in subcutaneous fat area (SFA), visceral fat area (VFA), and LFP were−66.5±7.9 cm2,−35.3±3.9 cm2, and−16.4±2.4%, respectively (allPvaluesP<0.0001). HOMA IR and HOMAβsignificantly decreased while whole body insulin sensitivity index (WBISI) increased (allPvaluesP<0.001).Conclusion. Eight weeks of VLCD was an effective intervention in obese subjects. These beneficial effects may be associated with enhanced hepatic and whole-body lipolysis and oxidation.

Enzymatic regulation of glucose disposal in human skeletal muscle after a high-fat, low-carbohydrate diet

2005 ◽  
Vol 98 (1) ◽  
pp. 100-107 ◽  
Author(s):  
Tanya L. Pehleman ◽  
Sandra J. Peters ◽  
George J. F. Heigenhauser ◽  
Lawrence L. Spriet
Keyword(s):  
Skeletal Muscle ◽  
Active Form ◽  
Whole Body ◽  
Glucose Disposal ◽  
Oral Glucose ◽  
Vastus Lateralis Muscle ◽  
High Fat ◽  
Carbohydrate Diet ◽  
Low Carbohydrate Diet ◽  
Low Carbohydrate

Whole body glucose disposal and skeletal muscle hexokinase, glycogen synthase (GS), pyruvate dehydrogenase (PDH), and PDH kinase (PDK) activities were measured in aerobically trained men after a standardized control diet (Con; 51% carbohydrate, 29% fat, and 20% protein of total energy intake) and a 56-h eucaloric, high-fat, low-carbohydrate diet (HF/LC; 5% carbohydrate, 73% fat, and 22% protein). An oral glucose tolerance test (OGTT; 1 g/kg) was administered after the Con and HF/LC diets with vastus lateralis muscle biopsies sampled pre-OGTT and 75 min after ingestion of the oral glucose load. The 90-min area under the blood glucose and plasma insulin concentration vs. time curves increased by 2-fold and 1.25-fold, respectively, after the HF/LC diet. The pre-OGTT fraction of GS in its active form and the maximal activity of hexokinase were not affected by the HF/LC diet. However, the HF/LC diet increased PDK activity (0.19 ± 0.05 vs. 0.08 ± 0.02 min−1) and decreased PDH activation (0.38 ± 0.08 vs. 0.79 ± 0.10 mmol acetyl-CoA·kg wet muscle−1·min−1) before the OGTT vs. Con. During the OGTT, GS and PDH activation increased by the same magnitude in both diets, such that PDH activation remained lower during the HF/LC OGTT (0.60 ± 0.11 vs. 1.04 ± 0.09 mmol acetyl-CoA·kg−1·min−1). These data demonstrate that the decreased glucose disposal during the OGTT after the 56-h HF/LC diet was in part related to decreased oxidative carbohydrate disposal in skeletal muscle and not to decreased glycogen storage. The rapid increase in PDK activity during the HF/LC diet appeared to account for the reduced potential for oxidative carbohydrate disposal.

scholarly journals Alternate Day Fasting Combined with a Low Carbohydrate Diet: Effect on Sleep Quality, Duration, Insomnia Severity and Risk of Obstructive Sleep Apnea in Adults with Obesity

Nutrients ◽  
2021 ◽  
Vol 13 (1) ◽  
pp. 211
Author(s):  
Faiza Kalam ◽  
Kelsey Gabel ◽  
Sofia Cienfuegos ◽  
Mark Ezpeleta ◽  
Eric Wiseman ◽  
...  
Keyword(s):  
Weight Loss ◽  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Sleep Quality ◽  
Weight Maintenance ◽  
Carbohydrate Diet ◽  
Low Carbohydrate Diet ◽  
Obstructive Sleep ◽  
Low Carbohydrate ◽  
Insomnia Severity

Background: Alternate day fasting combined with a low carbohydrate diet (ADF-LC) is an effective weight loss regimen. Whether the weight loss induced by ADF-LC can improve sleep, remains unknown. Objective: This study examined the effect an ADF-LC diet on sleep quality, duration, insomnia severity and the risk of obstructive sleep apnea. Methods: Adults with obesity (n = 31) participated in ADF (600 kcal “fast day”; ad libitum intake “feast day”) with a low-carbohydrate diet (30% carbohydrates, 35% protein, and 35% fat). The 6-month trial consisted of a 3-month weight loss period followed by a 3-month weight maintenance period. Results: Reductions in body weight (−5 ± 1 kg, p < 0.001) and fat mass (−4 ± 1 kg, p < 0.01) were noted during the weight loss period, and these reductions were sustained during the weight maintenance period. Lean mass and visceral fat remained unchanged. The Pittsburgh Sleep Quality Index (PSQI) score indicated poor sleep quality at baseline (6.4 ± 0.7) with no change by month 3 or 6, versus baseline. ISI score indicated subthreshold insomnia at baseline (8.5 ± 1.0), with no change by month 3 or 6, versus baseline. The percent of subjects with high risk of obstructive sleep apnea at baseline was 45%, with no change by month 3 or 6. Wake time, bedtime, and sleep duration remained unchanged. Conclusion: The ADF-LC diet does not impact sleep quality, duration, insomnia severity or the risk of obstructive sleep apnea in adults with obesity.

Sign in / Sign up

Export Citation Format

Share Document