Acute exercise does not decrease liver fat in men with overweight or NAFLD

Abstract

Elevated hepatic lipid content (IntraHepatic Lipid, IHL) increases the risk of metabolic complications. Although prolonged exercise training lowers IHL, it is unknown if acute exercise has the same effect. Furthermore, hepatic ATP content may be related to insulin resistance and IHL. We aimed to investigate if acute exercise leads to changes in IHL and whether this is accompanied by changes in hepatic ATP. Twenty-one men (age 54.8 ± 7.2 years, BMI 29.7 ± 2.2 kg/m2) performed a 2 h cycling protocol, once while staying fasted and once while ingesting glucose. IHL was determined at baseline, 30 min post-exercise and 4 h post-exercise. Additionally ATP/Total P ratio was measured at baseline and 4 h post-exercise. Compared with baseline values we did not observe any statistically significant changes in IHL within 30 min post-exercise in neither the fasted nor the glucose-supplemented condition. However, IHL was elevated 4 h post-exercise compared with baseline in the fasted condition (from 8.3 ± 1.8 to 8.7 ± 1.8%, p = 0.010), an effect that was blunted by glucose supplementation (from 8.3 ± 1.9 to 8.3 ± 1.9%, p = 0.789). Acute exercise does not decrease liver fat in overweight middle-aged men. Moreover, IHL increased 4 h post-exercise in the fasted condition, an increase that was absent in the glucose-supplemented condition. These data suggest that a single bout of exercise may not be able to lower IHL.

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“…Indeed, glucose ingestion during exercise causes plasma NEFA levels to decrease below fasting levels during and after exercise [36,42]. Accordingly, glucose supplementation during and after cycling prevents an increase in liver fat during the recovery phase [36]. Furthermore, studies with isoenergetic diets show a decrease in liver fat only with high-carbohydrate diets, not with high-fat diets [6,7].…”

“…A third possibility is that the participants did not refrain from exercise for 48 h before the examination as they were supposed to, leading to a decrease in muscle fat and an increase in liver fat. In healthy people with normal weight and in overweight individuals, an acute bout of aerobic exercise immediately increases liver fat [35,36]. This exercise-induced increase in liver fat seems to be mainly due to the rise in plasma NEFA during and after exercise [35,36].…”

“…In healthy people with normal weight and in overweight individuals, an acute bout of aerobic exercise immediately increases liver fat [35,36]. This exercise-induced increase in liver fat seems to be mainly due to the rise in plasma NEFA during and after exercise [35,36]. All participants in our study were told to refrain from exercise for 48 h prior to liver fat examination.…”

“…Suppression of adipose tissue lipolysis through insulin administration or carbohydrate ingestion leads to a reduction in plasma NEFA levels. Indeed, glucose ingestion during exercise causes plasma NEFA levels to decrease below fasting levels during and after exercise [36,42]. Accordingly, glucose supplementation during and after cycling prevents an increase in liver fat during the recovery phase [36].…”

Liver fat: a relevant target for dietary intervention? Summary of a Unilever workshop

“…Increasing the level of circulating NEFA in vivo , for example by performing acute exercise in the fasted state ( 20 ) , leads to an increase in cardiac and hepatic lipid content ( 21 ) . However, regular exercise training, leading to an improvement in oxidative capacity, lowers fat accumulation in liver and the heart ( 22 ) .…”