first blood
MuscleChemistry Member
The message is clear. The more fat you gain during an extended period of inactivity, the more muscle mass you lose.
Conclusion
“The present study shows that excess fat deposition during physical inactivity is associated with greater muscle loss […],” the researchers summarise. “These mechanisms potentially contribute to long-term changes in body composition and to the cardiometabolic risk observed in sedentary persons.”
The implications for athletes are clear. If they can’t train for an extended period, they’ll probably retain more muscle mass by making sure they don’t consume too many calories.
We wonder what would happen if inactive athletes go for a negative calorie balance in these longer periods, so that they lose a little fat mass? Will the muscle mass loss also increase? Or is it a way to reduce muscle mass even further?
Positive energy balance is associated with accelerated muscle atrophy and increased erythrocyte glutathione turnover during 5 wk of bed rest1,2,3
Abstract
Background
Physical inactivity is often associated with positive energy balance and fat gain.
Objective
We aimed to assess whether energy intake in excess of requirement activates systemic inflammation and antioxidant defenses and accelerates muscle atrophy induced by inactivity.
Design
Nineteen healthy male volunteers were studied before and at the end of 5 wk of bed rest. Subjects were allowed to spontaneously adapt to decreased energy requirement (study A, n = 10) or were provided with an activity-matched diet (study B, n = 9). Groups with higher (HEB) or lower (LEB) energy balance were identified according to median values of inactivity-induced changes in fat mass (ΔFM, assessed by bioelectrical impedance analysis).
Results
In pooled subjects (n = 19; median ΔFM: 1.4 kg), bed rest–mediated decreases in fat-free mass (bioelectrical impedance analysis) and vastus lateralis thickness (ultrasound imaging) were significantly greater (P < 0.03) in HEBAB (−3.8 ± 0.4 kg and −0.32 ± 0.04 cm, respectively) than in LEBAB (−2.3 ± 0.5 kg and −0.09 ± 0.04 cm, respectively) subjects. In study A (median ΔFM: 1.8 kg), bed rest–mediated increases in plasma leptin, C-reactive protein, and myeloperoxidase were greater (P < 0.04) in HEBA than in LEBA subjects. Bed rest–mediated changes of glutathione synthesis rate in eythrocytes (L-[3,3-2H2]cysteine incorporation) were greater (P = 0.03) in HEBA (from 70 ± 19 to 164 ± 29%/d) than in LEBA (from 103 ± 23 to 84 ± 27%/d) subjects.Conclusions Positive energy balance during inactivity is associated with greater muscle atrophy and with activation of systemic inflammation and of antioxidant defenses. Optimizing caloric intake may be a useful strategy for mitigating muscle loss during period of chronic inactivity.Source: http://ajcn.nutrition.org/content/88/4/950.long
Conclusion
“The present study shows that excess fat deposition during physical inactivity is associated with greater muscle loss […],” the researchers summarise. “These mechanisms potentially contribute to long-term changes in body composition and to the cardiometabolic risk observed in sedentary persons.”
The implications for athletes are clear. If they can’t train for an extended period, they’ll probably retain more muscle mass by making sure they don’t consume too many calories.
We wonder what would happen if inactive athletes go for a negative calorie balance in these longer periods, so that they lose a little fat mass? Will the muscle mass loss also increase? Or is it a way to reduce muscle mass even further?
Positive energy balance is associated with accelerated muscle atrophy and increased erythrocyte glutathione turnover during 5 wk of bed rest1,2,3
Abstract
Background
Physical inactivity is often associated with positive energy balance and fat gain.
Objective
We aimed to assess whether energy intake in excess of requirement activates systemic inflammation and antioxidant defenses and accelerates muscle atrophy induced by inactivity.
Design
Nineteen healthy male volunteers were studied before and at the end of 5 wk of bed rest. Subjects were allowed to spontaneously adapt to decreased energy requirement (study A, n = 10) or were provided with an activity-matched diet (study B, n = 9). Groups with higher (HEB) or lower (LEB) energy balance were identified according to median values of inactivity-induced changes in fat mass (ΔFM, assessed by bioelectrical impedance analysis).
Results
In pooled subjects (n = 19; median ΔFM: 1.4 kg), bed rest–mediated decreases in fat-free mass (bioelectrical impedance analysis) and vastus lateralis thickness (ultrasound imaging) were significantly greater (P < 0.03) in HEBAB (−3.8 ± 0.4 kg and −0.32 ± 0.04 cm, respectively) than in LEBAB (−2.3 ± 0.5 kg and −0.09 ± 0.04 cm, respectively) subjects. In study A (median ΔFM: 1.8 kg), bed rest–mediated increases in plasma leptin, C-reactive protein, and myeloperoxidase were greater (P < 0.04) in HEBA than in LEBA subjects. Bed rest–mediated changes of glutathione synthesis rate in eythrocytes (L-[3,3-2H2]cysteine incorporation) were greater (P = 0.03) in HEBA (from 70 ± 19 to 164 ± 29%/d) than in LEBA (from 103 ± 23 to 84 ± 27%/d) subjects.Conclusions Positive energy balance during inactivity is associated with greater muscle atrophy and with activation of systemic inflammation and of antioxidant defenses. Optimizing caloric intake may be a useful strategy for mitigating muscle loss during period of chronic inactivity.Source: http://ajcn.nutrition.org/content/88/4/950.long
