Low carbohydrate diet induces metabolic depression: a possible mechanism to conserve glycogen. - PubMed - NCBI
Long-term studies have found low carbohydrate diets are more effective for weight loss than calorie restricted diets in the short-term, but equally or only marginally more effective in the long-term. Low carbohydrate diets have been linked to reduced glycogen stores and increased feelings of fatigue. We propose that reduced physical activity in response to lowered glycogen explains the diminishing weight loss advantage of low carbohydrate compared to low calorie diets over longer time scales. We explored this possibility by feeding adult Drosophila melanogaster either a standard or low carbohydrate diet for nine days and measured changes in metabolic rate, glycogen stores, activity, and body mass. We hypothesized that a low carbohydrate diet would cause a reduction in glycogen stores that recovers over time, reduced physical activity, and an increase in resting metabolic rate. The low carbohydrate diet was found to reduce glycogen stores, which recovered over time. Activity was unaffected by diet but the low carbohydrate group experienced a reduction in metabolic rate. We conclude that metabolic depression could explain the decreased effectiveness of low carbohydrate diets over time and recommend further investigation of long-term metabolic effects of dietary interventions and a greater focus on physiological plasticity within the study of human nutrition.
Influence of high- and low-carbohydrate diet following glycogen-depleting exercise on heart rate variability and plasma catecholamines. - PubMed - NCBI
Abstract
The effects of simple-carbohydrate (CHO)- and complex-CHO-rich diets on skeletal muscle glycogen content were compared. Twenty male marathon runners were divided into four equal groups with reference to dietary consumption: depletion/simple, depletion/complex, nondepletion/simple, and nondepletion/complex. Subjects consumed either a low-CHO (15% energy [E] intake), or a mixed diet (50% CHO) for 3 days, immediately followed by a high-CHO diet (70% E intake) predominant in either simple-CHO or in complex-CHO (85% of total CHO intake) for another 3 days. Skeletal muscle biopsies and venous blood samples were obtained one day prior to the start of the low-CHO diet or mixed diet (PRE), and then again one day after the completion of the high-CHO diet (POST). The samples were analysed for skeletal muscle glycogen, serum free fatty acids (FFA), insulin, and lactate and blood glucose. Skeletal muscle glycogen content increased significantly (p less than 0.05) only in the nondepletion/simple group. When groups were combined, according to the type of CHO ingested and/or utilization of a depletion diet, significant increases were observed in glycogen content. Serum FFA decreased significantly (p less than 0.05) for the nondepletion/complex group only, while serum insulin, blood glucose, and serum lactate were not altered. It is concluded that significant increases in skeletal muscle glycogen content can be achieved with a diet high in simple-CHO or complex-CHO, with or without initial consumption of a low-CHO diet
Long-term studies have found low carbohydrate diets are more effective for weight loss than calorie restricted diets in the short-term, but equally or only marginally more effective in the long-term. Low carbohydrate diets have been linked to reduced glycogen stores and increased feelings of fatigue. We propose that reduced physical activity in response to lowered glycogen explains the diminishing weight loss advantage of low carbohydrate compared to low calorie diets over longer time scales. We explored this possibility by feeding adult Drosophila melanogaster either a standard or low carbohydrate diet for nine days and measured changes in metabolic rate, glycogen stores, activity, and body mass. We hypothesized that a low carbohydrate diet would cause a reduction in glycogen stores that recovers over time, reduced physical activity, and an increase in resting metabolic rate. The low carbohydrate diet was found to reduce glycogen stores, which recovered over time. Activity was unaffected by diet but the low carbohydrate group experienced a reduction in metabolic rate. We conclude that metabolic depression could explain the decreased effectiveness of low carbohydrate diets over time and recommend further investigation of long-term metabolic effects of dietary interventions and a greater focus on physiological plasticity within the study of human nutrition.
Influence of high- and low-carbohydrate diet following glycogen-depleting exercise on heart rate variability and plasma catecholamines. - PubMed - NCBI
Abstract
The effects of simple-carbohydrate (CHO)- and complex-CHO-rich diets on skeletal muscle glycogen content were compared. Twenty male marathon runners were divided into four equal groups with reference to dietary consumption: depletion/simple, depletion/complex, nondepletion/simple, and nondepletion/complex. Subjects consumed either a low-CHO (15% energy [E] intake), or a mixed diet (50% CHO) for 3 days, immediately followed by a high-CHO diet (70% E intake) predominant in either simple-CHO or in complex-CHO (85% of total CHO intake) for another 3 days. Skeletal muscle biopsies and venous blood samples were obtained one day prior to the start of the low-CHO diet or mixed diet (PRE), and then again one day after the completion of the high-CHO diet (POST). The samples were analysed for skeletal muscle glycogen, serum free fatty acids (FFA), insulin, and lactate and blood glucose. Skeletal muscle glycogen content increased significantly (p less than 0.05) only in the nondepletion/simple group. When groups were combined, according to the type of CHO ingested and/or utilization of a depletion diet, significant increases were observed in glycogen content. Serum FFA decreased significantly (p less than 0.05) for the nondepletion/complex group only, while serum insulin, blood glucose, and serum lactate were not altered. It is concluded that significant increases in skeletal muscle glycogen content can be achieved with a diet high in simple-CHO or complex-CHO, with or without initial consumption of a low-CHO diet
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