Skeletal muscle low attenuation area and maximal fat oxidation rate during submaximal exercise in male obese individuals

Abstract

BACKGROUND: Muscle triacylglycerols (TG) are known to be a source of energy during submaximal exercise. OBJECTIVE: The aim of this study was to assess whether an index of muscle fat content is related to maximal fat oxidation rate (FATOX max ) in 58 obese men (mean age 45.5 AE 0.8 (s.e.) y, body weight 95.3 AE 1.4 kg, percentage fat 31.1 AE 0.6%). DESIGN: FATOX max was defined as the highest value of fat oxidation rate, measured by indirect calorimetry, while walking on a treadmill (4.3 km=h) at three different slopes: 0% (40 AE 1% of VO 2max ), 3% (47 AE 1% of VO 2max ) and 6% (58 AE 1% of VO 2max ). Fat-free mass (FFM) and fat mass (FM) were measured with the underwater technique and scans were obtained by computed tomography (CT) at the mid thigh level to assess areas of adipose tissue within skeletal muscle, ie deep adipose tissue (DAT), subcutaneous adipose tissue (SAT), skeletal muscle (M) and low attenuation skeletal muscle (LAM, range of attenuation values 0 -34 Hounsfield units). LAM and DAT were used as indices of skeletal muscle fat content. RESULTS: FATOX max , adjusted for age, was correlated with FFM (r ¼ 0.25, P < 0.05), LAM (r ¼ 0.28, P < 0.05), DAT (r ¼ 0.23, P < 0.05), abdominal visceral adipose tissue (r ¼ 0.26, P < 0.05) and plasma free fatty acid (FFA) levels (r ¼ 0.36, P < 0.05) but not with SAT (r ¼ 0.07). In a stepwise linear multiple regression, plasma FFA, age and LAM significantly predicted FATOX max (r 2 ¼ 0.27). Each independent variable explained about 9% of the FATOX max variance. CONCLUSION: LAM makes a significant but weak contribution to the modulation of fat oxidation during submaximal exercise in obese men.

Measurement and Physiological Relevance of the Maximal Lipid Oxidation Rate During Exercise (LIPOXmax)

“…LIPOXmax SIN model initial publication Dériaz et al, 2001Achten et al, 2002Jeukendrup, 2003;Venables et al, 2005Brun et al, 2009b;Chenevière et al, 2009b …”

Long term (3 years) weight loss after low intensity endurance training targeted at the level of maximal muscular lipid oxidation

“…By contrast, low intensity endurance, that promotes lipid oxidation, has been proposed since almost twenty years as a promising strategy against obesity [8][9][10][11][12] .When targeted with exercise calorimetry at levels where lipid oxidation is maximal (LIPOXmax), it has been shown to improve mitochondrial respiration [13], blood glucose control and blood lipids, low grade inflammation and body composition, even at low weekly volume [14]. Surprisingly, this approach generated less literature, perhaps because its weight-reducing effects over the short term, although significant, were not spectacular.…”

“…At 1 year subjects with LIPOX max in the lower quartile (<35% VO2max n=23) lose less weight than the others (-2.3 ± 0.98 vs -5.4 ± 0.83 p=0,05) but this difference vanishes over time. This study shows that this low intensity exercise training maintains its weight-reducing effect 3 years while diet is no longer efficient, and that this effect is initially related to muscular ability to oxidize lipids but that metabolic and behavioral adaptations have been further developed and contribute to a long lasting effect.By contrast, low intensity endurance, that promotes lipid oxidation, has been proposed since almost twenty years as a promising strategy against obesity [8][9][10][11][12] .When targeted with exercise calorimetry at levels where lipid oxidation is maximal (LIPOXmax), it has been shown to improve mitochondrial respiration [13], blood glucose control and blood lipids, low grade inflammation and body composition, even at low weekly volume [14]. Surprisingly, this approach generated less literature, perhaps because its weight-reducing effects over the short term, although significant, were not spectacular.…”

Maximizing Acute Fat Utilization: Effects of Exercise, Food, and Individual Characteristics

“…Recent studies have examined the ideal volume (Bond Brill et al, 2002) or intensity (Achten et al, 2002;Bergman and Brooks, 1999;Deriaz et al, 2001) of exercise for maximizing fat utilization. The macronutrient composition (Whitley et al, 1997) and the effects of caloric content (Martin et al, 2000) of a meal on fat metabolism have also been the subject of recent study.…”